By Dr. John R. Mishock
There is a belief that resistance exercises or weightlifting create muscle damage, leading to tightness and limiting function in sports such as baseball, basketball, golf, and others. Does resistance exercise damage muscle? Can the muscle damage be helpful?
Resistance training exercise creates micro-damage to the muscle. This muscle damage is critical to the physiological cellular change needed for muscle adaptation. Muscle micro-damage is contrasted with muscle injury when the micro-damage becomes excessive, leading to muscle strain, inflammation, and pain. Individuals who follow proper resistance exercise training principles will not create injury or excessive tightness but will enhance most injury prevention and sports performance metrics. During exercise, the positive effects of muscle micro-damage occur when the exercise is novel, the intensity or volume increases, or the contraction type changes (concentric to eccentric or isometric). Regular manipulation of these variables can help to optimize the training effect found through muscle micro-damage. This article will describe how small amounts of muscle damage are critical for hypertrophy, strength, and power gains. Listed below are the physiological benefits of exercise created through muscle damage.
- Connective tissue matrix damage: Resistance exercise causes damage to muscle connective tissue matrix (sarcolemma, basal lamina, and supportive connective tissue, contractile elements, or actomyosin bonds). This matrix is the scaffolding that holds the muscle together. Small amounts of damage cause a strengthening of this matrix, allowing an enhanced base to create stronger muscle contractions. The strong connective tissue matrix can minimize or prevent muscle injury. (Clark et al. 2002)
- Repeated bout effect: Progressive resistance exercise stresses the muscle, causing larger numbers of muscle fibers to contract with increased muscle contraction efficiency and coordination. The repeat bout effect improves the movement pattern of the exercise while causing adaptation in muscle strength and hypertrophy. This neuro-muscular phenomenon is why exercise movements become more effortless in the first several weeks of training.
- Inflammatory cascade effect: Muscle microtrauma causes small amounts of inflammation triggered by immune cells (WBCs, neutrophils, macrophages). This inflammation facilitates tissue repair and regeneration. Macrophages (immune cells) release myokines (IL-6, IL7, IL8, IL 10), signally molecules that stimulate muscle hypertrophy and strength. Reactive oxygen species (superoxide, hydrogen peroxide, hydroxyl radical), released during inflammation, signal muscle growth and hypertrophy through increased protein synthesis (muscle building).This increased immune cell function is believed to enhance the body’s defenses against infections (Covid-19) and other diseases. (Peake et al. 2017)
- Protein synthesis (muscle building): Mechanical muscle trauma triggers protein synthesis during exercise. Muscle-building occurs through a complex physiological interaction (cyclooxygenase pathway (COX-2), ultimately creating the increased size (muscle hypertrophy) of existing muscle and the development of new muscle fibers. Adequate amounts of protein (1.6 g per lb body weight) are needed from the diet to maximize this muscle growth. (Clarkson et al. 1996) Without the protein, the muscle can not be built, further stressing the importance of good nutrition to optimize the training effect. Nonsteroidal anti-inflammatory drugs (NSAIDs), COX-2 inhibitors, can blunt the cellular response, possibly reducing muscle hypertrophy during exercise. Taking NSAIDs during training can be counterproductive to this process. It is theorized that individuals who take anti-oxidant supplements (Vitamin C, E, Curcumin) should take them on non-workout days to allow some of this inflammatory process. Antioxidants may help in muscle recovery (delayed muscle soreness (DOMS) when appropriate dosage and timing are utilized.
- Natural hormone production: Growth hormone (GH) and Insulin-like growth factor (IGF-1), anabolic hormones, are released by mechanical loading. IGF-1 and GH stimulate the rapamycin (mTOR) pathway, widely considered a master network for controlling skeletal muscle growth. These hormones also have a critical role in protein synthesis, which leads to muscle hypertrophy, strength, and power.
Can I create too much muscle micro-damage during resistance exercise training?
Not following proper training guidelines can lead to excessive muscle damage, reduced strength, lessened hypertrophy gains, excessive fatigue, and overuse injury. In these cases, the exercise reduces sports performance.
What is the best prescription for resistance exercise to optimize muscle micro-damage to create sports performance gains?
Progressive resistance exercise must follow strict training guidelines in;
- Volume (total amount of reps or sets): 2-3 sets of 5-15 reps with 3-5 exercises per body region.
- Load (amount of weight): The weight used should challenge the muscle while performing safe, effective movements. With proper weight during training, the individual should feel a “muscle burn” and challenge for the last 2-3 reps of the movement. The amount of load can also be determined in testing for the one rep max and then reducing the load by 20-40% for training.
- Frequency (training sessions per week): 2-3 training sessions per week.
- Intensity (effort per rep): A high-intensity and focused effort should be encouraged for every repetition.
- Rest/recovery (rest days between exercises): Between sets of an exercise, there should be 2-5 minutes between sets. During the rest period, a different muscle group or movement pattern can be trained (super set) to optimize time. There should be at least 24-48 hours between training sessions. High-quality sleep is essential, with most experts recommending 7-10 hours per night. During sleep is when muscle hypertrophy and strength adaptations occur.
- Changing the exercise routine or the exercise contraction type (concentric, isometric, and eccentric) every 4-to 12 weeks will enhance the muscle micro-damage.
For more in-depth details on training, check out my book (found on Amazon) “Fundamental Training Principles: Essential Knowledge for Building the Elite Athlete.”
Dr. Mishock is one of only a few clinicians with doctorate level degrees in both physical therapy and chiropractic in the state of Pennsylvania.
He has authored two books; “Fundamental Training Principles: Essential Knowledge for Building the Elite Athlete“, and “The Rubber Arm; Using Science to Increase Pitch Control, Improve Velocity, and Prevent Elbow and Shoulder Injury” both can be bought on Amazon.
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