Réf : Schoenfeld, B. J., & Contreras, B. (2013). Is Postexercise Muscle Soreness a Valid Indicator of Muscular Adaptations?. Strength & Conditioning Journal, 35(5).

Adaptation : Alexandre Paré - M.Sc.,CSCS. Kinésiologue

Introduction
Post-exercise muscle soreness (aches and pain) are a common manifestation of unusual or vigorous physical activity. It has been observed that many individuals who regularly practice resistance-based training consider that body soreness are, according to them, one of the best indicators of the effectiveness of their training. In fact, there has long been a belief that aches and pains are a necessary precursor to muscle remodeling.

1. Micro tears and Body Aches = TRUE

Current theory suggests that muscle aches are related to muscle breakdown resulting from excessive or unusual exercise. Although the exact mechanisms are poorly understood, soreness seem to be the product of inflammation caused by microtearing of the connective tissue that sensitize the nociceptors and thus increase the sensation of pain.

 

Soreness can be exacerbated by edema, swelling exerting pressure in the muscle fibers that stimulates the nociceptors. Muscle pains are more pronounced when training provides an unusual or new stimulus to the musculoskeletal system. Although concentric and eccentric training can induce aches, studies show that eccentric contractions have the most noticeable effect on the manifestation of soreness. As a general rule, the pain becomes noticeable about 6-8 hours after intense exercise and peaks about 48 hours after exercise.

The muscle micro tear resulting from intense training will result in 3 things:

• Inflammation: it is assumed that the acute inflammatory response to the lesion site would be an important mediator for future hypertrophic adaptations.
• Satellite cells: when stimulated by mechanical stress, satellite cells stimulate the proliferation of new cells that merge with existing ones, creating muscle tissue remodeling.
• Edema: micro tears are accompanied by an accumulation of fluids inside the muscle fiber. Cellular swelling is known to stimulate anabolism through combined protein synthesis and decreased protein degradation.

1. Micro tears and Hypertrophy = Uncertain

Despite popular belief, studies showing a cause-and-effect relationship between micro tear and hypertrophy are inconclusive.

Indeed, it has been shown that it is not mandatory to have muscle lesions to obtain hypertrophic adaptations.

In addition, it is important to note that excessive damage has a markedly negative effect on exercise performance and recovery, that is, severe muscle micro tear reduces strength production capacity by 50%. or more. Such a decrease will necessarily alter a person's ability to train again at high intensity, which would impair muscle growth. In addition, performing a training session during the rebuilding phase may slow down the overall recovery process.

Taking all factors into account, it can be assumed that micro tears can improve hypertrophic adaptations, but this theory is far from conclusive. Much like an inverted U-shaped curve, many biological systems adapt positively with moderate stress, but become strained when stress exceeds the acceptable limit. We can therefore believe that if micro tears actually promote muscle development, the optimal benefits would be obtained with mild to moderate damage. Unfortunately, the optimal degree of muscle damage to maximize growth, assuming there is one, remains to be determined.

2. Soreness and Hypertrophy = Uncertain

As mentioned earlier, it is true to say that muscle breakdowns cause muscle aches, but it is still questionable whether these soreness are an accurate indicator of the amount of muscle damage.

Here are 5 situations that tend to show that the degree of body soreness can not be a predictor of hypertrophy:

1. Absence of inflammation

As mentioned above, post-exercise inflammation is a precursor to tissue remodeling, but it has already been shown that it is possible to feel aches without showing local signs of inflammation. In a study of subjects who practiced different forms of unusual eccentric exercises (downhill run, eccentric bike and downhill stairs), the researchers found no inflammatory markers after exercise despite the presence of severe muscle soreness. These results justify caution when trying to use muscle soreness as a measure of muscle adaptations.

2. Type of contraction

It should also be mentioned that long-lasting concentric aerobic endurance tests (marathon and long distance bike rides) can cause many muscle soreness. These types of exercises are not usually associated with significant hypertrophic adaptations, indicating that pain alone is not necessarily contributive to growth.

3. Type of muscles

Anecdotally, many bodybuilders claim that some muscles are more sensitive to pain than others. They report that some muscles almost never experience muscle soreness, while others almost always experience it after training. Because bodybuilders have a marked hypertrophy of muscles that are and are not prone to aches, this casts doubt on the assumption that pain is mandatory for muscle development.

4. Type of exercises

Strength training exercises that place the peak tension at longer muscle lengths have also been shown to produce more pain than exercises that place peak tension at shorter muscle lengths. According to this concept, it would be conceivable that exercise that stress a muscle maximally at a short muscle length can promote hypertrophic gains without inducing pain.

5. Frequency

Another factor to consider is the frequency of strength training which has an effect on the extent of the aches. Indeed, the pain tends to dissipate when a muscle is subjected to repeated episodes of the same stimulus of effort. Therefore, the recurrent training of a muscle group would reduce the pain, while allowing to obtain impressive hypertrophic results.

Conclusion

Since muscle tearing is related to the hypertrophic process, it is justified to actively look for these lesions during a training session if hypertrophy is the desired goal. Since aches and pains are a general indicator of micro tears, pain can provide raw information about whether they have occurred. On the other hand, some strategies exist to minimize the soreness, like to repeat the same exercises, to carry out only the concentric phase of the movements and to execute only exercises which apply the maximum tension in position of the shortened muscle. Some muscles seem more prone to soreness than others and high levels of pain should be considered dangerous, as this is a sign that the athlete has exceeded the ability of the muscle to repair itself effectively.

These examples remind us that caution should be exercised in developing qualitative conclusions given the low correlation between body soreness and the extent of muscle breakdown.

Thus, the use of the degree of body pain in the evaluation of the quality of a training is limited, and therefore should not be used as a predictor of the results of hypertrophy.