INTRODUCTION TO VBT Velocity Based Training (VBT) emerged in the 1990s as a new approach to strength and power training, providing a strategy to increase the sports performance of traditional methods of programming and periodization. This technique utilizes bar speed technology to provide objective data on athletes' performance, allowing for real-time adjustments to any given workout[2]. As bar speed monitoring technology became more accessible and affordable, VBT gained traction in many team weight rooms, offering coaches and athletes a more precise way to calibrate training stressors. As the technology has become more available, individuals can now incorporate the technology into their own programming. At its core, VBT is not a specific program or routine, but rather an objective methodology for understanding an athlete's performance during strength training exercises[1]. It involves measuring the speed of movement which is usually a barbell. The speed is usually measured in meters per second (m/s), for compound movements such as squats, deadlifts, bench presses, and Olympic lifts[2]. By tracking metrics like average speed, and peak velocity, VBT enables coaches and athletes to individualize training programs based on each athlete's readiness and fatigue levels, ensuring optimal performance and reducing the risk of injuries[3]. This data-driven approach addresses the challenges of traditional planning methods, providing valuable insights that were previously difficult to obtain without sophisticated technology. The concept of "heavy" is relative in strength training. For one athlete, a 225-pound back squat might be impossible, while for another, it's only a warm-up. This relativity applies not only between different athletes but also to an individual athlete's training sessions over time. Using the 33% rule, approximately one-third of our training days are average, another third are better than average, and the remaining third are below average. Velocity-Based Training (VBT) provides a valuable tool for athletes and coaches to optimize performance. It allows them to capitalize on good days by pushing harder and to adjust accordingly on less optimal days by reducing intensity. UNDERSTANDING VBT Velocity-Based Training (VBT) is essentially about measuring the speed at which an athlete moves a weight during exercise. Unlike traditional percentage-based training methods, VBT focuses on the velocity of movement rather than solely on the weight lifted. This approach allows for real-time adjustments to training loads based on an athlete's daily performance capabilities. At its core, VBT is built on the principle of the load-velocity relationship, which states that there's an inverse correlation between the weight being lifted and the speed at which it can be moved. By monitoring movement velocity, coaches can gain insights into an athlete's current strength levels, fatigue state, and readiness. This information enables more precise control over training intensity and volume, leading to more individualized and effective workout sessions. VBT also incorporates the concept of velocity zones, where specific speed ranges are targeted to achieve different training outcomes such as power development or strength gains[9][12]. BENEFITS OF VBT IN SPORT The largest strength of VBT is in its ability to adapt training to an athlete's daily physiological state. Unlike standard training protocols that use fixed workout plans, VBT allows for real-time adjustments based on an athlete's current measurements. Some days an athlete might feel incredibly strong, while other days they may need a less intense workout - VBT helps identify and respond to these variations. Athletic performance is the primary goal of VBT. By tracking velocity, athletes can develop more explosive power and speed, which are critical in many sports. The method provides objective information about an athlete's strength, allowing for more targeted and effective training strategies. Coaches and athletes can now see exactly how an athlete is moving and progressing, rather than relying on subjective assessments. LIMITATIONS OF VBT While Velocity-Based Training (VBT) has earned a place in athletic circles, its application for the general population is less beneficial. EQUIPMENT AND COST BARRIERS For the general population, the specialized equipment or app subscriptions required for VBT cannot be worth the expense. High-quality velocity measurement devices are often expensive and may not be easy to use in a mainstream gym. This cost factor can make VBT less accessible to the average fitness enthusiast compared to sport focused athletes or well-funded sports teams. TECHNICAL COMPLEXITY Information used improperly may do more harm than good. VBT requires a certain level of technical knowledge to implement effectively. While athletes often have access to trained coaches who can interpret the data, the general population may struggle to understand and apply VBT principles correctly[9]. This can lead to misuse or ineffective implementation of the training method. TIME AND EFFORT INVESTMENT Setting up VBT equipment and analyzing the data can be time-consuming. For busy individuals in the general population, this additional time investment may not be practical or desirable, especially when compared to more straightforward training methods[8]. RELEVANCE TO FITNESS GOALS Many individuals in the general population have fitness goals that differ from those of athletes. While VBT excels in developing power and speed, which are crucial for athletic performance, these may not be primary objectives for the average gym-goer focused on general health, weight management, or basic strength gains[9]. PSYCHOLOGICAL FACTORS The constant feedback and data from VBT devices might be overwhelming or demotivating for some individuals in the general population. Unlike athletes who are accustomed to performance metrics, regular gym-goers might find the continuous measurement stressful or distracting from their workout experience. This is sometimes called “analysis by paralysis”. OVEREMPHASIS ON SPEED When used improperly VBT's focus on movement speed might lead to an overemphasis on velocity in movements that velocity is not a primary factor. For the general population, factors like proper form, consistency, and overall workout enjoyment are often more critical than measuring bar speed[10]. HOW TO MEASURE VBT VBT requires specialized equipment or apps to measure movement velocity accurately. The equipment based systems use Linear Position Transducers (LPTs). These devices are mounted to the floor or rack and a cable to the bar. As the bar moves the cable moves as well. This speed is measure by the equipment. The app systems generally use cameras to measure bar speed. COMMON TOOLS INCLUDE: 1. Linear Position Transducers Popular devices include GymAware, Vitruve encoder, and Enode. 2. Accelerometer-based devices 3. Video analysis software 4. Smartphone apps (e.g., Metric VBT app) Popular apps include Metric, TrueRep VBT, and My Jump Lab REPETITIONS AND SETS VBT allows for flexible rep schemes. The most common approach is to determine a desired speed and continue performing reps until the velocity drops below a certain threshold (e.g., 10% below the target velocity). This ensures quality reps and accounts for daily fluctuations in performance[3]. EXERCISE SELECTION VBT is most effective with compound, multi-joint exercises that allow for a full range of motion. Examples include squats, bench presses, deadlifts, and Olympic lifts. These movements provide the most transfer to athletic performance[2][5]. Measuring the speed of a bicep curl has little no real life value. IMPLEMENTING VBT IN YOUR WORKOUTS Steps to implement VBT: 1. Choose a velocity zone based on your training goal (e.g., strength, power, speed)[6]. 2. Select an initial weight and perform the movement as explosively as possible[6]. 3. Adjust the weight based on the measured velocity to match your target velocity zone[6]. 4. Continue adjusting until you find the appropriate load for your target velocity[6]. * Target velocities will be discussed later in this article. SAMPLE VBT WORKOUT Here's a basic VBT workout structure: 1. Main lift (e.g., Squat): 5 sets of 3 reps at 0.5-0.7 m/s 2. Power movement (e.g., Jump Squat): 3 sets of 5 reps at >1.0 m/s 4. 3. Accessory lift (e.g., Bench Press): 4 sets of 5 reps at 0.4-0.6 m/s LOAD SELECTION In VBT, load selection is somewhat of a moving target and based on the desired velocity. Generally individuals start with a moderate weight and adjust based on the measured velocity. If the velocity is too high, increase the weight; if it's too low, decrease it[6]. Recall that Velocity-Based Training (VBT) uses bar speed (measured in meters per second, or m/s) to guide training intensity and ensure athletes are working toward specific performance goals. The chart provided outlines the relationship between bar speed, training goals, and approximate load percentages (% of 1-rep max or 1RM). Here's a breakdown of each training goal and what it means: 1. STARTING STRENGTH - Bar Speed:> 1.3 m/s - Load:Very light weights (typically <30% of 1RM) - Purpose: This phase focuses on developing the ability to initiate movement quickly from a dead stop. It’s often used to improve neuromuscular efficiency and is critical for beginners or athletes recovering from injury. The light load allows for explosive movement without fatiguing the muscles. 2. SPEED-STRENGTH - Bar Speed:1.0 – 1.3 m/s - Load:~30–40% of 1RM - Purpose: Speed-strength emphasizes moving light-to-moderate loads as quickly as possible. This is ideal for athletes who need to generate high power output in sports requiring rapid acceleration (e.g., sprinters, jumpers). The focus is on speed rather than maximum force. 3. STRENGTH-SPEED - Bar Speed:0.75 – 1.0 m/s - Load:~40–65% of 1RM - Purpose: Strength-speed is about producing high force at relatively high velocities. It’s a balance between speed and strength, making it valuable for athletes in power sports like weightlifting, football, or rugby. This zone builds explosive power while still maintaining some velocity. 4. ACCELERATIVE STRENGTH - Bar Speed: 0.5 – 0.75 m/s - Load:~65–80% of 1RM - Purpose: Accelerative strength focuses on moving heavier loads with controlled speed. It bridges the gap between power and maximal strength development, helping athletes improve their ability to lift heavy weights explosively. 5. ABSOLUTE STRENGTH - Bar Speed: < 0.5 m/s - Load: ~85–100% of 1RM - Purpose: Absolute strength is the maximum amount of force an athlete can generate regardless of speed. Training in this range builds raw strength and is essential for powerlifters or anyone aiming to increase their maximum lifts (e.g., squats, deadlifts). 6. 1RM THRESHOLD - Bar Speed: ~0.3 m/s - Load:Maximum load (100% of 1RM) - Purpose: This represents the slowest bar speed at which you can still complete a lift successfully. It’s typically used to test an athlete’s true one-rep max (1RM). Bar speed below this threshold often results in failed lifts. KEY TAKEAWAYS - As bar speed decreases, the load increases, shifting the focus from speed and explosiveness to raw strength. - Each training goal corresponds to specific athletic needs: - Lighter weights and faster speeds develop power and explosiveness. - Heavier weights and slower speeds build strength. - Intermediate zones (speed-strength and strength-speed) combine elements of both.

Time Under Tension: A Comprehensive Look at an Effective Strength Training Method Time Under Tension (TUT) has emerged as a powerful and scientifically-backed approach to strength training, offering benefits for muscle growth, strength gains, and overall fitness. This article attempts to explain and simplify the concept of TUT, exploring its mechanisms, benefits, and practical applications in detail. UNDERSTANDING TIME UNDER TENSION Time Under Tension refers to the total duration a muscle is under strain during a resistance training set[1]. It encompasses the entire range of motion in an exercise, including the concentric (lifting), isometric (holding), and eccentric (lowering) phases. TUT is calculated by multiplying the duration of each movement phase by the number of repetitions performed[1]. For example, in a pull-up with a 3-second concentric phase, 3-second isometric hold at the top, and 3-second eccentric phase, the TUT for one repetition would be 9 seconds[1]. Conversely, those that participate in Crossfit can complete a full pullup rep in less than one second. THE SCIENCE BEHIND TUT Research has shown that manipulating TUT can significantly impact muscle growth and strength development. A study by Burd et al. (2012) demonstrated that prolonged muscle TUT affects protein synthesis and recovery, highlighting the importance of not only exercise volume but also manipulating eccentric loading to increase muscle fatigue[2]. MUSCLE FIBER RECRUITMENT TUT training enhances muscle fiber recruitment and activation. By extending the duration of each repetition, more muscle fibers are engaged throughout the movement, leading to greater mechanical tension and metabolic stress. This prolonged engagement stimulates the muscle fibers to adapt and grow stronger. Muscle fiber recruitment refers to the process by which the nervous system activates muscle fibers to produce force and movement. This recruitment follows the size principle, which prioritizes the activation of smaller, more fatigue-resistant fibers (Type I) before larger, more force-generating ones (Type IIa and Type IIb) as the force demand increases. During TUT training, the extended time under load allows for a more complete recruitment of muscle fibers across all types. As the exercise progresses and fatigue sets in, additional motor units are activated to maintain the required force output. This progressive recruitment ensures that a larger proportion of muscle fibers, including those that might not be engaged during shorter duration repetitions, are stimulated. The increased activation of fast-twitch fibers (Type IIb) during prolonged tension is particularly beneficial for muscle growth, as these fibers have the greatest potential for hypertrophy. The sustained tension created by TUT training enhances metabolic stress within the muscle, leading to greater accumulation of metabolic byproducts. This metabolic environment further contributes to muscle fiber activation and the subsequent adaptive responses that promote muscle growth.. METABOLIC STRESS AND BENEFICIAL MUSCLE DAMAGE Increasing TUT, particularly during the eccentric phase, elevates metabolic stress within the muscle. This "pump" feeling is associated with increased anabolic signaling and hormone responses[1]. Additionally, the extended time under load induces more significant beneficial muscle fiber damage, which leads to repair and contributes to muscle growth and strength gains[3]. PROTEIN SYNTHESIS Protein synthesis is a fundamental process in muscle growth and adaptation. The study published in The Journal of Physiology provides valuable insights into how time under tension (TUT) affects this crucial mechanism. The researchers found that greater muscle time under tension significantly increased the acute amplitude of protein synthesis in different muscle protein fractions. Especially when using the SLOW method. "SLOW" refers to a specific training condition where the tempo of the exercise is deliberately extended to increase time under tension (TUT). In this condition, participants performed resistance exercises with a significantly slower tempo, specifically using a 6-second concentric phase (the lifting portion of the exercise) and a 6-second eccentric phase (the lowering portion). Specifically: 1. Myofibrillar protein synthesis: The SLOW method (6-second concentric and eccentric actions) resulted in a higher myofibrillar protein synthetic rate compared to the control condition after 24-30 hours of recovery[14]. This delayed stimulation of myofibrillar protein synthesis is particularly important for muscle growth, as myofibrillar proteins are the primary structural components of muscle fibers. 2. Mitochondrial and sarcoplasmic protein synthesis: Exercise-induced rates of mitochondrial and sarcoplasmic protein synthesis were elevated by 114% and 77%, respectively, above resting levels at 0-6 hours post-exercise, but only in the SLOW condition[14]. This rapid increase in protein synthesis for these fractions suggests that TUT may have significant effects on muscle metabolism and non-contractile proteins. 3. Prolonged effect: Mitochondrial protein synthesis rates remained elevated above resting levels during the 24-30 hour recovery period in both the SLOW (175%) and control (126%) conditions[14]. This indicates that the effects of increased TUT on protein synthesis can persist for an extended period after exercise. BENEFITS OF TIME UNDER TENSION TRAINING 1. Enhanced Muscle Growth (Hypertrophy): By extending the time muscles spend under load, TUT creates greater metabolic stress and muscle damage, stimulating muscle fibers to adapt and grow[3]. 2. Improved Strength: The prolonged tension forces muscles to work harder, potentially leading to increased strength gains over time[5]. 3. Enhanced Muscle Endurance: Longer TUT (40-70 seconds per set) is particularly effective for developing muscle endurance and definition[5]. 4. Joint-Friendly Training: Using lighter weights with TUT can reduce stress on joints and ligaments, potentially lowering injury risk while still providing an effective stimulus for muscle growth[2]. 5. Breaking Through Plateaus: TUT introduces a novel stimulus to muscles, helping overcome training plateaus and promoting continuous progress[3]. 6. Versatility: TUT principles can be applied to various exercises and fitness levels, making it suitable for beginners and experienced athletes alike[3]. UNDERSTANDING TIME UNDER TENSION NOTATION When you see a time under tension (TUT) notation like #-#-#-#-#, each number represents a specific phase of the exercise. Here's what each number typically corresponds to: 1. Eccentric phase: The lowering or lengthening of the muscle 2. Bottom pause: The pause at the end of the eccentric phase 3. Concentric phase: The lifting or shortening of the muscle 4. Top pause: The pause at the end of the concentric phase 5. Transition: The time to start the next repetition (if applicable) For example, in a 4-1-2-1-0 tempo: 4 seconds for the eccentric phase 1 second pause at the bottom 2 seconds for the concentric phase 1 second pause at the top 0 seconds transition (immediate start of next rep) METHODS OF INCORPORATING TIME UNDER TENSION 1. Slow-tempo reps: Focuses on extending the duration of each repetition Increases muscle fiber recruitment and activation Example: 3-1-3-0 tempo for bicep curls[2] 2. Increased volume: Involves performing more repetitions or sets Extends overall time under tension without changing rep speed Example: Increasing from 8 to 12 reps per set[5] 3. Drop sets: Performing a set, then immediately reducing weight and continuing Prolongs muscle engagement without rest Best suited for isolation exercises[5] 4. Isometric holds: Incorporating pauses at various points in the movement Increases time under tension without changing rep count Example: Pausing at the bottom of a squat for 2-3 seconds 5. Full range of motion: Emphasizing complete extension and contraction Increases time under tension naturally Example: Full depth in squats or full extension in pull-ups IMPLEMENTING TUT IN YOUR WORKOUTS Steps to incorporating TUT: 1. Control the Tempo: Use a specific tempo for each phase of the movement. For example, a 3-2-5-0 tempo for bicep curls means 3 seconds up, 2 seconds pause, 5 seconds down, and no pause at the bottom[2]. 2. Adjust Duration: For muscle growth, aim for a TUT of 20-40 seconds per set. For endurance, extend this to 40-70 seconds[5]. 3. Reduce Weight: You may need to decrease the weight to maintain proper form throughout the extended repetitions[3]. 4. Focus on Form: Maintain strict form throughout the movement to maximize muscle engagement and minimize injury risk[3]. 5. Progressive Overload: Gradually increase the TUT or weight as you adapt to the training stimulus. SAMPLE TUT WORKOUT Here's an example of a TUT-focused workout: 1. Push-ups: 4 sets of 8 reps, 5 seconds on the way down 2. Squats: 4 sets of 10 reps, 5 seconds on the way down 3. Bent-over rows: 3 sets of 8 reps, 3 seconds up and 3 seconds down 4. Machine leg curls: 3 sets of 8 reps, 3 seconds up and 3 seconds down[3] To simplify the Time Under Tension (TUT) method, we can incorporate the 2-2-2 tempo approach. This straightforward technique makes it easier for both trainers and clients to implement TUT effectively in their workouts. IMPLEMENTING THE SLOW METHOD The slow method, also known as super slow resistance training, is a technique that emphasizes controlled, deliberate movements to maximize muscle tension and stimulate growth. SLOW TEMPO AND TIMING Use a specific tempo for each repetition, typically following a pattern like 10-4 or 6-6. For example: 10 seconds for the concentric (lifting) phase 4 seconds for the eccentric (lowering) phase Alternatively, some protocols suggest: 6 seconds for the concentric phase 6 seconds for the eccentric phase LOAD SELECTION Reduce the weight you normally use by about 30% to accommodate the slower tempo. This allows for better control and sustained tension throughout the movement. REPETITIONS AND SETS Perform fewer repetitions per set, typically 4 to 6, due to the increased time under tension. One set per exercise is often sufficient when using this method, as it leads to complete muscle fatigue. EXERCISE SELECTION Choose compound exercises that allow for smooth, controlled movements. Exercises like squats, chest presses, rows, and pull-downs are well-suited for the slow method. SIMPLIFYING TUT WITH THE 2-2-2 METHOD The 2-2-2 method is a simplified way to apply Time Under Tension principles to your exercises. Here's how it works: 1. Eccentric phase (lowering): 2 seconds 2. Pause at the bottom: 2 seconds 3. Concentric phase (lifting): 2 seconds This approach creates a total of 6 seconds per repetition, making it easy to calculate and maintain consistent tension throughout the set. BENEFITS OF THE 2-2-2 METHOD 1. Simplicity: The 2-2-2 tempo is easy to remember and apply to various exercises. 2. Consistency: It provides a uniform approach across different movements. 3. Balanced tension: Equal time is spent on each phase of the movement, ensuring comprehensive muscle engagement. 4. Adaptability: The method can be adjusted for different fitness levels by increasing or decreasing the number of repetitions. IMPLEMENTING THE 2-2-2 METHOD To use this simplified TUT approach: 1. Choose an appropriate weight that allows you to maintain proper form for 8-12 repetitions. 2. Apply the 2-2-2 tempo to each repetition. 3. Focus on maintaining control and tension throughout the entire range of motion. 4. Adjust the number of repetitions based on your goals and fitness level. By using the 2-2-2 method, you can effectively incorporate TUT principles into your workouts without the need for complex tempo schemes or calculations. This simplified approach makes it easier to focus on proper form and muscle engagement, potentially leading to better results in muscle growth and strength development. ADVANCED TUT TECHNIQUES 1. Eccentric Emphasis: Focus on slowing down the eccentric phase of the movement, as this has been shown to be particularly effective for muscle growth[1]. 2. Isometric Holds: Incorporate pauses at various points in the range of motion to increase time under tension and challenge stability. 3. Drop Sets: Perform a set to near failure, then immediately reduce the weight and continue with more repetitions, maintaining the TUT principle. 4. Supersets: Combine two exercises targeting the same muscle group, performing them back-to-back with minimal rest to maximize TUT. LIMITATIONS & CONSIDERATIONS ON SPORTS PERFORMANCE While Time Under Tension (TUT) training can be beneficial for muscle hypertrophy, it has several limitations when it comes to sports performance: 1. Reduced Power Output: TUT training, with its emphasis on slower movements, may negatively impact an athlete's ability to generate explosive power[22]. This can be detrimental for sports requiring quick, powerful movements. 2. Decreased Rate of Force Development: Studies have shown that TUT training can have negative effects on the rate of force development[22]. This is crucial for many sports where rapid force production is essential. 3. Strength Gains: Research indicates that TUT training may lead to fewer strength gains compared to traditional training methods[22]. For many sports, maximal strength is a key component of performance. 4. Sport-Specific Speed: The slow, controlled movements in TUT training do not mimic the velocities used in most competitive sports, potentially limiting transfer to actual performance[23]. 5. Time Efficiency: TUT workouts typically take longer to complete, which may not be ideal for athletes with limited training time[21]. 6. Fatigue Management: Prolonged time under tension can lead to increased fatigue, potentially affecting overall workout performance and recovery[21]. 7. Neuromuscular Adaptations: TUT training may not optimally stimulate the high-threshold motor units necessary for developing explosive strength and power[23]. CONCLUSION Time Under Tension is a scientifically method for enhancing muscle growth, strength, and endurance. By adjusting the duration of muscle contractions, TUT training offers a different stimulus that can lead to improvements in strength training and physique. For both novice and experienced athletes, incorporating TUT principles into your workout routine can provide new stimuli and help break through training plateaus. SOURCES:  [1] https://www.muscleandmotion.com/tension-hypertrophy/ [2] https://www.trainheroic.com/blog/volume-vs-time-under-tension-for-hypertrophy/

INTRODUCTION Your body is amazing at adapting to what you do regularly. This is called the SAID principle, which stands for Specific Adaptation to Imposed Demands. In simple terms, it means your body changes based on how you use it or in a way, don’t use it. For example, people who spend a lot of time on their phones often develop a hunched posture because their bodies adapt to that position. Their hamstrings get longer, hip flexors get shorter, and their chest muscles tighten up. On the other hand, people who lift heavy weights muscles get stronger. Those who do a lot of steady state, slow cardio exercise improve their ability to utilize oxygen by improving uptake at the cell level and increase their heart and lung function. The SAID principle is important in exercise science. It helps professionals and their athletes create specified workout plans. By understanding this principle, coaches can make sure training routines match their population(s) fitness & performance goals. Whether a person wants to build muscle, improve endurance, or just stay healthy, using the SAID principle will ensure that the training plan will result in the desire adaptations. This article will provide an introduction into the SAID principle. Future articles will expand on incorporating the SAID principle into various training programs. AEROBIC TRAINING AND THE SAID PRINCIPLE The SAID principle in aerobic training leads to specific cardiovascular and muscular adaptations. Regular aerobic exercise improves heart function, increases stroke volume, and enhances oxygen delivery to muscles. It also develops slow-twitch muscle fibers, increases capillary density at the tissues, boosts mitochondrial density, improves fat metabolism, and enhances neuromuscular efficiency. The body adapts to utilize energy systems specific to the duration and intensity of training. For example, a person that only trains at or near lactate threshold will have neither VO2max or aerobic capacity, but will increase their bodies ability to utilize and clear lactate. To apply the SAID principle effectively, match training intensity and duration to your goals, progressively increase training volume, and incorporate sport-specific movements. STRENGTH TRAINING AND THE SAID PRINCIPLE In strength training, the SAID principle is evident through neuromuscular adaptations, and movement pattern specificity. Specific strength exercises improve neural recruitment and synchronization of muscle fibers. Different loading schemes target fast-twitch or slow-twitch muscle fibers, and strength gains are most pronounced in the specific movements trained. To apply this principle, choose exercises that mimic your sport or daily activities, vary rep ranges and loading schemes, and progressively overload exercises to continue challenging the muscles and nervous system. HYPERTROPHY TRAINING AND THE SAID PRINCIPLE For muscle growth, the SAID principle guides adaptations in muscle fiber hypertrophy and metabolism. Specific training protocols lead to increases in muscle fiber size, and the body adapts to handle increased workload and nutrient demands for muscle growth. To apply this principle in hypertrophy training, focus on exercises targeting specific muscle groups, utilize appropriate rep ranges and time under tension, and progressively increase volume and intensity to continue stimulating muscle growth. SPORT-SPECIFIC TRAINING AND THE SAID PRINCIPLE The SAID principle is crucial in sport-specific training, emphasizing movement pattern specificity and skill acquisition. Training should replicate the exact movements and energy systems used in the sport, and repeated practice of sport-specific skills leads to neural adaptations that improve performance. To apply this principle, analyze the demands of your sport, design training programs that mimic those demands, incorporate drills replicating game scenarios, and progressively increase the complexity and intensity of sport-specific exercises. THE SAID PRINCIPLE & MALADAPTATIONS FROM A SEDENTARY LIFESTYLE While the SAID principle is often discussed in the context of positive adaptations from exercise, it's equally applicable to understanding negative adaptations or maladaptations that occur from prolonged sedentary behaviors, such as sitting. For example, take a person that has an 8 hour desk job with a 45-60 minute commute. They workout for 45 minutes in the evening, commuting 15 minutes to and from the gym where their cool off period is mostly the way home from the gym. Below is the standard adaptations expected with a person that fits this criteria. POSTURAL CHANGES Prolonged sitting imposes specific demands on the body, leading to adaptations that can be detrimental to overall musculoskeletal health. The seated position keeps the hip flexors in a shortened state, which can result in adaptive shortening over time. This constant flexed position at the hips can lead to tightness and reduced flexibility in these muscles. Additionally, the glutes and hamstrings remain largely inactive during sitting, potentially leading to weakness and reduced activation in these important muscle groups [1]. The tendency to hunch forward while sitting can also have negative consequences, often resulting in a rounded upper back. This posture can lead to adaptive shortening of chest muscles and a corresponding lengthening of upper back muscles, contributing to poor posture and potential discomfort or pain in the upper body. These adaptations highlight the importance of regular movement and postural awareness to counteract the effects of prolonged sitting [1]. MUSCULAR IMBALANCES The SAID principle (Specific Adaptation to Imposed Demands) provides insight into how prolonged sitting can lead to significant postural changes and muscular imbalances. As the body adapts to the demands of extended periods in a seated position, it develops specific muscular patterns that can have far-reaching effects on posture and overall musculoskeletal health. For instance, the combination of tight pectoral muscles and weak upper back muscles often results in rounded shoulders and a forward head posture, altering the natural alignment of the upper body. Similarly, the shortening of hip flexors, coupled with the weakening of gluteal muscles due to inactivity, can significantly impact pelvic positioning. This imbalance can potentially contribute to lower back pain and other related issues. These adaptations underscore the importance of understanding the SAID principle in the context of sedentary behaviors and highlight the need for targeted interventions to counteract these negative postural changes [1]. METABOLIC ADAPTATIONS Prolonged sitting not only affects our musculoskeletal system but also imposes significant metabolic demands, or more accurately, a lack thereof, on our bodies. The extended periods of inactivity, particularly in the large leg muscles, can lead to decreased insulin sensitivity and an increase in fat concentration in the blood. This reduction in muscle activity means that our bodies are not actively using energy as they would during movement or standing. As a result, the body begins to adapt to this low-energy state, potentially leading to reduced metabolic efficiency over time. These adaptations can have far-reaching consequences for our overall health, contributing to issues such as weight gain, increased risk of type 2 diabetes, and cardiovascular problems. Understanding these metabolic adaptations underscores the importance of regular movement and activity breaks, even in environments that require extended periods of sitting. COUNTERACTING SEDENTARY ADAPTATIONS Understanding these maladaptations through the lens of the SAID principle can help in designing effective strategies to counteract them: 1. Regular movement breaks : Interrupting long periods of sitting with short bouts of activity can help prevent these adaptations[1]. You can go for a short walk every 45 minutes or better yet, perform a one minute bout of high intensity exercise, such as burpees or jumping jacks. 2. Targeted exercises: Incorporating exercises that specifically address the muscles affected by prolonged sitting (e.g., hip flexor stretches, glute strengthening exercises) can help reverse these adaptations[1]. 3. Ergonomic adjustments: Modifying the work environment to encourage better posture and more movement throughout the day can help impose different demands on the body[1]. Try to incorporate a stand up desk or choose to stand when possible. SUMMARY The SAID (Specific Adaptation to Imposed Demands) principle is a fundamental concept in exercise science and physiology that explains how the human body adapts to the stresses placed upon it. This principle applies to both positive adaptations from exercise and negative adaptations from sedentary behavior. In the context of exercise, the SAID principle guides the development of targeted training programs. For aerobic training, it leads to cardiovascular improvements, enhanced oxygen delivery, and increased muscular endurance. In strength training, it results in neuromuscular adaptations, changes in muscle fiber types, and movement-specific strength gains. Hypertrophy training focuses on muscle growth through specific protocols that increase muscle fiber size and metabolic efficiency. Additionally, sport-specific training emphasizes replicating exact movements and energy systems used in particular sports to improve performance. However, the SAID principle also explains maladaptations that occur due to prolonged sedentary behavior. For instance, sitting for extended periods can lead to postural changes such as shortened hip flexors, weakened glutes and hamstrings, and rounded upper backs. These adaptations contribute to muscular imbalances, including tight pectorals and weak upper back muscles, which can alter pelvic positioning. Furthermore, sedentary behavior can negatively impact metabolic health by decreasing insulin sensitivity and reducing overall metabolic efficiency. To counteract these negative adaptations, it is crucial to incorporate regular movement breaks and targeted exercises that address the specific demands of prolonged sitting. Understanding and applying the SAID principle is essential for designing effective exercise programs, improving athletic performance, and maintaining overall health in our increasingly sedentary society. SOURCES [1] https://www.ptpioneer.com/personal-training/certifications/study/said-principle/ [2] https://www.ptpluswellness.com/post/maximize-your-workouts-understanding-the-said-principle-in-fitness-training [3] https://www.bettermovement.org/blog/2009/0110111 [4] https://www.simplesolutionsfitness.com/said-principle [5] https://www.freeletics.com/en/blog/posts/said-training-principle/ [6] https://en.wikipedia.org/wiki/SAID_principle [7] https://www.mdpi.com/2411-5142/7/4/76 [8] https://oshwiki.osha.europa.eu/en/themes/musculoskeletal-disorders-and-prolonged-static-sitting [9] https://safunctionalfitness.com/said-principle/ [10] https://www.freeletics.com/en/blog/posts/said-training-principle/ [11] https://www.ptpluswellness.com/post/maximize-your-workouts-understanding-the-said-principle-in-fitness-training [12] https://williamsonsource.com/the-said-principle-explained-how-and-why-the-body-requires-time-for-adaptations/ 

INTRODUCTION Hypertrophy Specific Training (HST) is a scientifically-based workout program designed to maximize muscle growth through targeted exercises and progressive overload. HST focuses on stimulating muscle hypertrophy - the increase in size of muscle cells - through specific training principles and techniques. Unlike traditional bodybuilding approaches, HST is grounded in the physiological mechanisms that drive muscle growth. It incorporates key factors like mechanical load, training frequency, and strategic deconditioning to optimize the hypertrophy response. Whether you're an experienced lifter looking to break through a plateau or a beginner aiming to build lean mass efficiently, HST offers a systematic framework to achieve your muscle-building goals. This article will explore the core principles of HST, debunk common myths surrounding hypertrophy training, and examine the numerous benefits this approach can offer - from improved body composition to enhanced athletic performance. We'll also provide practical insights on how to implement HST effectively in your own training regimen. Get ready to dive deep into the science of muscle growth and discover how HST can transform your physique. WHAT IS HYPERTROPHY SPECIFIC TRAINING? The word hyper/trophy in its parts means hyper - above/beyond - Trophy - growth. Hypertrophy Specific Training (HST) is a scientifically-based workout program designed to maximize muscle growth through targeted exercises and progressive overload. HST focuses on stimulating muscle hypertrophy - the increase in size of muscle cells - through specific training principles and techniques. In simple terms, HST is a systematic approach to increase muscle size. BREAKING THE MYTHS RELATED TO HST MYTH #1: HST WILL MAKE WOMEN LOOK LIKE MEN One of the most persistent myths is that women who engage in hypertrophy training will develop bulky, masculine physiques. This fear is largely unfounded. Women typically have much lower levels of testosterone compared to men, which makes it difficult for them to build large amounts of muscle mass. In reality, hypertrophy training can help women achieve a toned, lean appearance while improving overall strength and body composition. MYTH #2: HST IS BAD FOR ENDURANCE ATHLETES Contrary to popular belief, hypertrophy training can be beneficial for endurance athletes. While it's true that excessive muscle mass can be detrimental to endurance performance, a well-designed hypertrophy program can actually enhance an athlete's capabilities. Increased muscle strength and power can improve running economy, cycling efficiency, and overall performance in endurance events[3]. MYTH #3: HST ALWAYS LEADS TO WEIGHT GAIN Many people assume that hypertrophy training inevitably results in significant weight gain. However, this is not always the case. Hypertrophy training primarily focuses on increasing muscle fiber diameter and improving force generation capacity. These adaptations can occur without substantial changes in overall body weight, especially when combined with proper nutrition and endurance training. BENEFITS OF HST PHYSICAL BENEFITS 1. Increased Muscle Size: The primary goal of hypertrophy training is to increase muscle size. Increased muscle size allows for a greater strength development. Improves a person’s physique and in sports like football, the extra mass increases a person’s interia, their resistance to be moved or to be stopped from moving [6][7]. 2. Improved Strength: While not as focused on maximal strength as a strength training program, hypertrophy training still significantly increases overall strength[7]. Just like an engine, the larger the size, the greater force it can generate. 3. Enhanced Athletic Performance: Larger, stronger muscles can generate more force, potentially improving performance in various sports and activities [7]. 4. Better Body Composition: Hypertrophy training can help increase lean muscle mass while decreasing body fat percentage [7]. HEALTH BENEFITS 1. Improved Joint and Bone Health: All resistance training, including hypertrophy work, can enhance joint stability and increase bone density[8]. 2. Metabolic Boost: Muscle is akin to being the engine of the human body. Increased muscle mass leads to a higher resting metabolic rate, helping with weight management and energy expenditure[6][7]. 3. Better Insulin Sensitivity: When exercising, especially at high intensities, glycogen (glucose) is the primary energy source for muscle cells. This increases the cell's sensitivity to glucose which in terms reduces the risk of insulin resistance and type 2 diabetes[7]. 4. Cardiovascular Health: All exercise will provide some benefits for cardiovascular health. While this is generally not the focus with HST. There's evidence that resistance training may reduce the risk of cardiovascular disease[8]. FUNCTIONAL AND LONG-TERM BENEFITS 1. Maintained Functional Movement: Hypertrophy training helps maintain lean muscle mass and functional movement abilities as you age[8]. 2. Reduced Injury Risk: Stronger muscles and improved joint stability can lower the risk of injuries in daily activities and sports[6]. 3.Improved Mood and Mental Health: Like other forms of exercise, hypertrophy training releases endorphins, which can enhance mood and confidence[6]. 4. Long-term Health: Research suggests that resistance training is linked to a reduced risk of all cause mortality, including cancer and cardiovascular disease[8]. KEY PRINCIPLES OF HST MECHANICAL LOAD This principle is all about putting enough stress on your muscles to make them grow. It's like challenging your muscles to lift heavy things. When you do this, your body thinks, "I need to get stronger to handle this!" and starts building more muscle. HST makes sure you're lifting weights that are heavy enough to trigger this growth response. PROGRESSIVE OVERLOAD Think of this as gradually making things harder for your muscles. Whether you are increasing the weight, number of sets or reps. In progressive overload you are continually increasing the demand in the muscles. This demand causes them to adapt to whatever stimulus is imposed. This often referred to as the SAID principle. Specific Adaptation to an Imposed Demand. FREQUENT STIMULUS Hypertrophy training, aimed at increasing muscle size, requires a delicate balance between stimulus and recovery. Recent research and practical experience suggest that an optimal approach involves training each muscle group twice a week with approximately 72 hours of rest between sessions targeting the same muscle group. The 72-Hour Recovery Window The 72-hour rest period between training sessions for the same muscle group is based on several physiological factors: Muscle Protein Synthesis (MPS): Studies indicate that MPS peaks around 24-36 hours post-exercise and can remain elevated for up to 48-72 hours in trained individuals.Muscle Damage Recovery: Most muscle damage markers return to baseline within 48-72 hours after a training session, allowing for adequate recovery. Training Each Muscle Group Twice A Week Training each muscle group twice a week aligns with current research on optimal training frequency for hypertrophy: It allows for sufficient volume distribution throughout the week. This frequency has been shown to promote superior hypertrophic outcomes compared to once-weekly training. It provides a good balance between stimulus and recovery for most individuals. There is some evidence that training 3 days a week with 48 hours of rest may be beneficial. STRATEGIC DECONDITIONING This is a more sophisticated way of expressing "planned rest periods." When one consistently engages in the same training regimen, the body can adapt to the stimulus, resulting in diminished progress. Hypertrophy-Specific Training (HST) incorporates phases where training intensity is reduced or altered. This approach functions similarly to pressing a reset button for the muscles, enhancing their responsiveness when intense training resumes. COMPOUND EXERCISES These are exercises that work multiple muscle groups at once. Instead of just doing bicep curls (which only work your biceps), HST focuses on exercises like squats or bench presses that work several muscles together. It's like killing two (or more) birds with one stone. This approach is more efficient and often leads to better overall muscle growth and strength gains. For example, the best way to get big biceps is by incorporating a supinated grip barbell bent over rows. INCORPORATING HYPERTROPHY INTO SPORTS PERFORMANCE PERIODIZATION IS KEY When it comes to hypertrophy and sport, hypertrophy must be incorporated with intention and planning. Often periodized training programs will alternate between hypertrophy-focused phases and sports-specific performance phases. This approach allows for muscle growth while maintaining and improving sport-specific skills[3]. - Off-season: Focus more on hypertrophy training - Pre-season: Gradually shift towards more sport-specific training - In-season: Maintain muscle mass with minimal hypertrophy work, prioritize sports performance COMPOUND MOVEMENTS FOR DUAL BENEFITS Incorporate compound exercises that mimic sports-specific movements. These exercises build muscle mass while improving functional strength relevant to your sport[4]. EXAMPLES - Olympic lifts; For explosive power - Squats and deadlifts; for overall lower body strength - Pull-ups and rows; for upper body development SPORT-SPECIFIC HYPERTROPHY Target muscle groups crucial for your sport. This approach ensures that the muscle mass gained directly contributes to improved performance[5]. EXAMPLES - Swimmers; Focus on lats, shoulders, and core - Sprinters; Emphasize quadriceps, hamstrings, and glutes - Basketball players; Target legs for jumping power and upper body for shooting strength BALANCE VOLUME AND INTENSITY Carefully manage training volume and intensity to avoid overtraining and ensure recovery for sports practice and competition[3]. - Use lower volume, higher intensity workouts during the competitive season - Increase volume during off-season for maximum hypertrophy gains FUNCTIONAL HYPERTROPHY TRAINING Incorporate exercises that improve both muscle size and sports-specific skills: - Medicine ball throws; for rotational power and core hypertrophy - Plyometric push-ups; for explosive upper body strength - Bulgarian split squats; for unilateral leg development and balance NUTRITION FOR GROWTH AND PERFORMANCE Tailor your diet to support both muscle growth and athletic performance: - Increase protein intake to support muscle hypertrophy - Consume adequate carbohydrates for energy during sports training - Time nutrient intake around workouts and competitions for optimal performance RECOVERY AND ADAPTATION Prioritize recovery to allow for both muscle growth and skill development: - Implement deload weeks to prevent overtraining - Use active recovery techniques like light cardio or yoga - Ensure adequate sleep for muscle repair and skill consolidation By strategically combining hypertrophy training with sports-specific work, athletes can build muscle mass that directly contributes to improved performance in their chosen sport. This integrated approach ensures that gains in size translate to enhanced strength, power, and overall athletic ability on the field or court. Citations: [1] https://dr-muscle.com/hypertrophy-specific-training/ [2] https://www.backbayfit.com/post/hypertrophy-specific-training (3) [1] https://pmc.ncbi.nlm.nih.gov/articles/PMC10487730/ [4] https://www.sci-sport.com/en/articles/Concurrent-training-Does-cardio-affect-muscle-mass-and-strength-gains-233.php [5] https://www.backbayfit.com/post/hypertrophy-specific-training [6] https://www.kelseywells.com/blogs/lifestyle/hypertrophy-training [7] https://www.backbayfit.com/post/hypertrophy-specific-training [8] https://www.onepeloton.com/blog/hypertrophy-vs-strength-training/

1. Training Methods Overview: - 80/20: 80% low-intensity (Zone 2), 20% high-intensity (Zones 4-5) - 60/40: 60% low-intensity (Zone 2), 40% high-intensity (Zones 4-5) 2. 80/20 Method: - Popular among endurance athletes - Benefits: Maximizes aerobic endurance, reduces injury risk, improves long-duration performance - Implementation: Long, slow distance (80%), intervals/tempo runs (20%) - Best for: Long-distance runners, cyclists, triathletes 3. 60/40 Method: - More balanced approach - Benefits: Develops aerobic and anaerobic systems, versatile, time-efficient - Implementation: Steady-state workouts (60%), intervals/sprints/plyometrics (40%) - Best for: Multi-disciplinary athletes, sports requiring endurance and power 4. Zone 2 Training: - Characteristics: Low-intensity, conversational pace - Benefits: Improves aerobic capacity, fat oxidation, builds aerobic base - Metrics: 60-70% max heart rate, 55-75% lactate threshold - Volume: 180-480 minutes/week (method dependent) 5. Zone 5 Training: - Characteristics: High-intensity, maximal effort - Benefits: Improves VO2 max, anaerobic capacity, power output - Metrics: 90-100% max heart rate, 100-120% lactate threshold - Volume: 15-60 minutes/week (method dependent) 6. Age Considerations: - Younger (20s-30s): More Zone 5 work (2-3 sessions/week) - Middle-aged (40s-50s): Reduce Zone 5 (1-2 sessions/week) - Older (60+): Limit Zone 5 (once/week or less)

INTRODUCTION Training intensity and duration distribution is an essential aspect of any endurance training program. Intensity is usually measured in terms of % of maximum heart rate or rating of perceived exertion (RPE). While duration is the length of each session. A program that does not take into consideration the benefits and risks of both modalities will fail to meet the athletes training goals and will potentially lead to burnout and/or injury. Two popular methods are the 60/40 and 80/20 approaches, which differ in how they allocate time between low (zone 2) and high-intensity (zone 5) work. This article will compare Zone 2 and Zone 5 training within these frameworks, discussing their benefits, risks, and optimal implementation. By understanding these methods, coaches and athletes can tailor their training to enhance endurance, power, and overall performance. THE 60/40 vs 80/20 TRAINING METHODS The 60/40 and 80/20 training methods are two approaches to balancing the distribution of low-intensity and high-intensity workouts within an athlete's training regimen. The key difference between them lies in the proportion of time spent in each training intensity zone. 80/20 METHOD The 80/20 training method has gained significant popularity among endurance athletes, offering a structured approach to balancing workout intensity. This method allocates 80% of training time to low-intensity aerobic exercise (typically Zone 2) and 20% to high-intensity workouts (Zones 4 and 5). Long-distance runners, cyclists, and triathletes particularly favor this approach for its ability to build a strong aerobic base while incorporating enough high-intensity work to improve speed and VO2 max. BENEFITS OF THE 80/20 METHOD 1. Maximizes aerobic endurance 2. Reduces risk of injury and overtraining 3. Improves overall performance in long-duration sports 4. Allows for consistent training volume IMPLEMENTING THE 80/20 METHOD - Low-intensity workouts (80%): Long, slow distance runs, easy bike rides, or relaxed swims - High-intensity workouts (20%): Interval training, tempo runs, hill repeats CONSIDERATIONS While the 80/20 method is highly effective for endurance sports, athletes in power-based or sprint-focused disciplines may find it lacking in terms of power and speed development. These athletes might need to adjust the ratio to include more high-intensity training. By prioritizing low-intensity training, athletes can build a solid foundation of aerobic fitness while minimizing the risk of burnout or injury. The strategic incorporation of high-intensity sessions ensures continued improvement in speed and power, creating a well-rounded training program for endurance athletes. 60/40 METHOD The 60/40 training method offers a more balanced approach to intensity distribution in athletic training. This method allocates 60% of training time to low-intensity, aerobic exercise (typically Zone 2) and 40% to higher-intensity workouts (Zones 4 and 5). This strategy caters to athletes who require a closer ratio of endurance and power, making it particularly suitable for sports demanding both sustained effort and explosive performance. KEY FEATURES OF THE 60/40 METHOD 1. Versatility: Develops both aerobic endurance and anaerobic power 2. Balanced approach: Suitable for athletes with diverse performance needs 3. Time-efficient: Higher proportion of high-intensity training can lead to rapid improvements IMPLEMENTING THE 60/40 METHOD - Low-intensity workouts (60%): Steady-state runs, moderate cycling, or swimming - High-intensity workouts (40%): Interval training, sprints, plyometrics, or sport-specific drills CONSIDERATIONS While the 60/40 method offers a well-rounded approach, it requires careful management: 1. Increased recovery needs due to higher intensity training volume 2. Greater risk of overtraining if not properly monitored 3. May not be suitable for pure endurance athletes or beginners The 60/40 method provides a dynamic training structure that can enhance both endurance and power. However, coaches must pay close attention to their athletes' response and adjust as needed to prevent fatigue and optimize performance gains. This approach is ideal for multi-disciplinary athletes or those seeking a more varied training regimen. ZONE 2 vs ZONE 5 COMPARISON ZONE 2 TRAINING Zone 2 is typically defined as the low-intensity aerobic training zone, often referred to as "conversational pace." It is usually characterized by a steady, sustainable effort that can be maintained for extended periods. Training in Zone 2 primarily targets the aerobic energy system and has 3 major effects. 1. Improves the efficiency of the cardiovascular system 2. Increases capillary density at the tissue level. 3. Increases mitochondrial density at the cellular level which increases the body's ability to burn fat as a fuel source. BENEFITS - Improves aerobic capacity and fat oxidation - Enhances capillary & mitochondrial density and efficiency - Builds a strong aerobic base for higher-intensity work - Low risk of injury and quick recovery DOWNFALLS/RISKS - Can be mentally tedious - May not provide enough stimulus for experienced athletes if overused - The high volume increases the risk of overuse injuries HEART RATE METRICS - 60-70% of max heart rate - 55-75% of lactate threshold TRAINING VOLUME - 80/20 method: 240-480 minutes per week - 60/40 method: 180-360 minutes per week - Minimum effective dose: 30-45 minutes per session for novice, 60-90 minutes for advanced ZONE 5 TRAINING Zone 5 is the high-intensity anaerobic training zone, often associated with maximal effort. Often referred to as HIIT workouts. It involves pushing the body's limits with short bursts of intense exercise, focusing on speed, power, and anaerobic capacity. Training in Zone 5 targets the anaerobic energy system and is commonly used to improve an athlete's top-end speed and power output. BENEFITS - Significantly improves VO2 max - Enhances anaerobic capacity and power output - Boosts metabolic rate and fat burning post-exercise - Efficient for time-constrained individuals DOWNFALLS/RISKS - High risk of injury if not properly executed or executed with a novice athlete/client. - Requires longer recovery periods - Can lead to burnout if overused HEART RATE METRICS - 90-100% of max heart rate - 100-120% of lactate threshold TRAINING VOLUME - 80/20 method: 15-30 minutes per week (not counting rest between sets) - 60/40 method: 30-60 minutes per week (not counting rest between sets) - Minimum effective dose: 4-5 minutes per session (in intervals) IMPACT OF AGING As we age, our ability to recover from high-intensity exercise diminishes. While Zone 2 training remains beneficial throughout life, Zone 5 training should be adjusted: - Younger athletes (20s-30s): Can handle more Zone 5 work, up to 2-3 sessions per week - Middle-aged athletes (40s-50s): Should reduce Zone 5 sessions to 1-2 per week - Older athletes (60+): May benefit from limiting Zone 5 work to once per week or less It's crucial to listen to your body and adjust training intensity based on individual recovery capacity. As we age, the 80/20 method often becomes more appropriate, emphasizing a larger base of Zone 2 work with strategic, limited use of Zone 5 training. CONCLUSION Zone 2 and Zone 5 training offer unique benefits. The 80/20 method prioritizes building a strong aerobic base with targeted high-intensity work, while the 60/40 approach allows for more frequent high-intensity sessions. The optimal balance depends on individual goals, age, and recovery capacity. Regardless of the chosen method, incorporating both zones into a training plan can lead to well-rounded fitness improvements. SOURCES: [1] https://athletica.ai/captivate-podcast/balancing-intensity-the-science-behind-the-80-20-training-principle/ [2] https://www.8020endurance.com/new-study-strikes-fatal-blow-to-80-20-training-philosophy/ [3] https://www.reddit.com/r/running/comments/o0qo5l/we_need_to_talk_about_the_8020_rule/ [4] https://www.forum.8020endurance.com/topic/high-intensity-distribution-in-training-plans/ [5] https://www.bogleheads.org/forum/viewtopic.php?t=233488 [6] https://trainingdayfitness.co/blogs/news/what-is-the-80-20-intensity-balance-rule-can-it-improve-your-endurance [7] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4030606/ [8] https://nutrabio.com/blogs/blog/tudca-5-key-benefits-for-bodybuilders-liver-support

Heart Rate Training Zones