A client completes a new lower-body session and spends the next two days negotiating the stairs. Another completes a familiar session, feels relatively comfortable afterward, and wonders whether the workout was demanding enough. For personal trainers, delayed-onset muscle soreness creates an important coaching problem: the client can feel the response, but cannot directly observe the adaptation.
Specifically, soreness, muscle damage, and hypertrophy describe different things. Soreness is an experience; damage refers to disruption of tissue; hypertrophy is an increase in muscle size over time. Treating them as interchangeable encourages clients to chase a sensation when the program is supposed to develop a capacity.
October’s first series considered how exercise fits into a working week. Here, the question shifts to what clients believe a successful session should leave behind. NFPT’s Recovery 101 for New Personal Trainers provides broader recovery context. This article examines the narrower issue of what soreness can—and cannot—tell us about muscle growth.
In this article, we will examine:
- Why soreness is an imperfect indicator of muscle damage.
- How adaptation can continue as soreness diminishes.
- How to use symptom reports without making discomfort a programming target.
Three Related Responses, Three Different Questions
Delayed-onset muscle soreness, commonly shortened to DOMS, develops after exercise rather than being felt during the immediate effort of a set. Unfamiliar exercise, particularly actions in which an active muscle lengthens, can produce it. The lowering phase of a curl is one example of this eccentric muscle action. Cleveland Clinic’s DOMS guidanceexplains the typical delayed pattern and the need to seek help for unusually severe symptoms.
However, a sensation is not a tissue biopsy. Nosaka and colleagues (2002) studied 110 male students performing different numbers of maximal eccentric elbow-flexor actions. Soreness generally correlated poorly with other indirect indicators of damage. The relationship also depended on whether soreness was assessed during palpation, flexion, or stretching.
Consequently, asking how sore a client feels is useful, but translating that answer into a precise estimate of tissue damage is not justified. Equally, the absence of soreness cannot certify that every aspect of muscle function has recovered. This controlled elbow-flexor experiment informs interpretation; it does not supply a universal readiness test for an adult completing a full-body program.
To illustrate, consider the difference between noticing that a room is noisy and measuring how much useful work occurred inside it. The noise tells us something about the experience, but cannot establish the quality of the work. Soreness has a similar limitation: it deserves attention without becoming the final verdict on training.
What Happens When the Body Becomes Familiar With the Work?
The repeated bout effect describes a protective adaptation in which a previous exposure to eccentric exercise reduces damage from a subsequent bout. McHugh’s (2003) review considered possible neural, mechanical, and cellular contributions while emphasizing that a unified explanation remained unresolved. We should resist reducing this response to one convenient mechanism.
For coaching purposes, the important implication is that the same exercise need not produce the same soreness indefinitely. A client becoming less uncomfortable after repeated exposure has not necessarily stopped responding to training. Changing exercises solely to restore soreness may replace useful familiarity with unnecessary novelty.
This does not mean that a familiar program should remain unchanged forever. Loads, repetitions, and other demands still require thoughtful progression. The distinction is between progressing an exercise because the client’s capacity warrants it and changing the exercise because discomfort has disappeared.
Damage Is Not a Required Receipt for Growth
Flann and colleagues (2011) compared a group introduced gradually to eccentric cycling with a group exposed to an initially damaging bout. Both then completed an eight-week eccentric-cycling program with work equated between groups. Despite different initial signs of damage, gains in muscle size and strength did not differ significantly.
This supports an important, bounded conclusion: detectable initial damage was not required for adaptation in that experiment. It does not establish that all forms of muscle damage are biologically irrelevant, or that every resistance-training method produces identical outcomes. It does challenge the assumption that a client must first be made substantially sore to benefit.
Damas and colleagues (2016) examined another part of the question in 10 young men completing 10 weeks of lower-limb resistance training. The initial postexercise increase in myofibrillar protein synthesis (e.g., the production of proteins within muscle’s contractile machinery) was largest when damage was greatest. That early response did not correlate with eventual hypertrophy. Later synthesis responses, after damage had diminished, were related to growth.
These findings illustrate why a large acute response should not automatically be called a better long-term result. Early synthesis may help repair and remodel tissue rather than represent newly accumulated muscle alone. The small, specific sample also prevents us from prescribing an exact adaptation timetable for every client.
Introduce Novelty Without Introducing a New Problem
When introducing an unfamiliar exercise, I would begin by considering what is actually new. The movement may be new, the range may be new, or the amount of work may have changed. Increasing several demands at once makes the subsequent response harder to interpret.
As a hypothetical example, a client already accustomed to bilateral squatting begins split squats. The trainer can introduce a modest amount of practice, assess control, and ask about the response afterward before adding substantial work. The goal is to learn how this person tolerates the movement, not to prove that the exercise deserves its reputation for creating soreness.
Record what changed and what followed. Did discomfort interfere with walking, normal activity, or the next planned session? Did the client move differently to avoid it? These observations help determine whether the introduction needs adjustment. They are coaching information, not a diagnosis of damaged tissue.
NFPT’s recent Recovery is Part of the Workout discusses the broader need to consider several signals together. Within a soreness-focused conversation, that means asking what the symptom is doing to function instead of treating its intensity as the program’s report card.
Respect Symptoms Without Practicing Medicine
A trainer should not relabel every pain report as ordinary DOMS. Sharp or persistent pain, substantial swelling, or symptoms that don’t improve warrant medical assessment. CDC/NIOSH guidance identifies unexpectedly severe muscle pain, dark urine, and unusual weakness or inability to complete familiar tasks as possible warning signs of rhabdomyolysis. Seek medical attention immediately for those signs; do not attempt to clear the client through another workout.
Even when soreness seems consistent with an ordinary exercise response, it does not permit forcing a painful movement. Adjusting the session, using a comfortable alternative, or allowing more recovery can be reasonable coaching choices. A trainer cannot establish tissue safety from a soreness score, and symptom relief should not be treated as proof that normal loading is appropriate.
Give Clients a More Useful Explanation
A practical explanation might be: “The new exercise may explain why you feel different afterward. We will pay attention to that response, but we do not need to recreate it every week to make progress.” This acknowledges the client’s experience without awarding discomfort special status.
Then connect the next decision to the program’s purpose. Retain an exercise when it continues to serve that purpose and can be performed appropriately. Progress it when the client is ready. Reconsider it when the response repeatedly disrupts the training plan or ordinary activity. None of those decisions requires soreness to become a badge of commitment.
Ultimately, soreness belongs in the conversation because clients experience it. It should not govern the conversation simply because it is easy to notice. Effective coaching helps clients distinguish the immediate sensation from the longer process of adaptation—and gives them a reason to trust productive work that does not announce itself on tomorrow’s staircase.
References
Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health. (2025). Signs and symptoms of rhabdomyolysis. https://www.cdc.gov/niosh/rhabdo/signs-symptoms/index.html
Cleveland Clinic. (2025). Delayed onset muscle soreness (DOMS).https://my.clevelandclinic.org/health/diseases/delayed-onset-muscle-soreness
Damas, F., Phillips, S. M., Libardi, C. A., Vechin, F. C., Lixandrão, M. E., Jannig, P. R., Costa, L. A. R., Bacurau, A. V., Snijders, T., Parise, G., Tricoli, V., Roschel, H., & Ugrinowitsch, C. (2016). Resistance training-induced changes in integrated myofibrillar protein synthesis are related to hypertrophy only after attenuation of muscle damage. The Journal of Physiology, 594(18), 5209–5222. https://doi.org/10.1113/JP272472
Flann, K. L., LaStayo, P. C., McClain, D. A., Hazel, M., & Lindstedt, S. L. (2011). Muscle damage and muscle remodeling: No pain, no gain? Journal of Experimental Biology, 214(4), 674–679. https://doi.org/10.1242/jeb.050112
McHugh, M. P. (2003). Recent advances in the understanding of the repeated bout effect: The protective effect against muscle damage from a single bout of eccentric exercise. Scandinavian Journal of Medicine & Science in Sports, 13(2), 88–97. https://doi.org/10.1034/j.1600-0838.2003.02477.x
Nosaka, K., Newton, M., & Sacco, P. (2002). Delayed-onset muscle soreness does not reflect the magnitude of eccentric exercise-induced muscle damage. Scandinavian Journal of Medicine & Science in Sports, 12(6), 337–346. https://doi.org/10.1034/j.1600-0838.2002.10178.x
