Perspiration is a natural human process that serves important purposes, yet so many of us revile its effects in both ourselves and others. Some people don’t like to be stinky, some don’t like to be slimy, and most don’t want to be close to others who are either! Personal trainers are forever intertwined with exercise-induced sweat and so, likely do not regard it with as much disdain as some of our clients. Here’s how we can help our clients make peace with the perspiration process and teach them about the benefits of sweating.

No Sweat is No Good

Evaporated sweat moderates body temperatures whether or not the cause is strenuous exercise or exposure to hot environments 1. While sweat is odorless, topical bacteria in hairy areas of the body can cause odor and wetness when a person is anxious or stressed  – right?

  • Deodorants and antiperspirants make up a $5 Billion market segment in the USA – which Statista equates to an average annual cost of ~$15 per consumer. Saddlebag, under-arm sweat is not good in a big business meeting, yet that category known as apocrine sweat is not the topic of this post. Rather, eccrine sweat from about 3 million sweat glands is as it relates to clients’ training, exercise, and healthspan.

Professional trainers must be aware of potential heat-related stressors, regardless of the season or temperature or workout intensity, when coaching or working with their clients. We are trained to know the dangers of heat stroke, and to recognize possible indicators for this potentially dangerous condition – headache, confusion, no sweating, rapid heart rate, nausea or vomiting, and loss of consciousness.

No sweat is no good.

Here are three points of perspiration we will ponder ahead:

  • Human sweat processes also aid other important bodily functions 1a.
  • Exercise-induced sweat 2 may extend a client’s healthspan.
  • A client’s readiness checklist for chasing the biology of bliss (as addressed by author and ultra-marathoner Chris Bergland) 3 is also summarized for safety and client satisfaction.

Human Sweat Functions


Some adults can lose up to 4 liters (1 gallon) of sweat per hour with exertion and/or heat. That is about eight pounds of coolant exchanged per hour in bodily attempts to maintain homeostasis in fairly extreme cases. Our sweaty coolant is mostly water, sodium chloride, and potassium. Trace compounds like lactates and micronutrients are also excreted.

Note: Every client is different. Two clients of the same size, age, and gender may exhibit dramatically different sweat processes. Clients may need several days to re-absorb potassium and sodium from diet and drink to offset muscle cramps.

Recall that one’s athletic performance degrades after about two percent of body weight is lost in sweat and exhalations. The training platitude to drink a little before thirst sets in is spot-on, as it can take about ten minutes or more to absorb “simple” hydrations on an empty stomach. If your client is a stamina-focused endurance athlete, bear in mind that staying power can be reduced by half when dehydrated.


Negative performance impacts include: reduced blood volume, reduced sweating, increased core temperature, and increased glycogen use by skeletal muscles.4  However, drinking too much water during an endurance activity can be harmful or even deadly as sodium exchanges at the cellular level are limited in a condition known as hyponatremia.5

  • Cleansing

A tiny percentage of “normal” eccrine sweat is comprised of ammonia or urea, salts, sugar, and glycoproteins.  Professional researchers do not agree on whether sweating from activity, a sauna session or a hot bath can add “detoxification” roles for pollutants – chemicals, contaminants, and heavy metals – to this list. Without full double-blind or clinical experiments, this “detox” disagreement may not resolved. There is credible evidence that sweating can eliminate certain skin bacteria.

  • Healthspan boosts
    • Skin cell nourishment – from increased circulation of blood – can give clients a “dewy” healthy appearance
    • Endorphin boosts from runners’ highs (30 – 50 minutes of low to moderately intense aerobics)
    • Boosted self-confidence
    • Improved mental health with restorative sleep.

Exercise-induced Sweat and its Benefits

When a client works in a focused strength or stamina lesson of tailored intensity and duration, she or he triggers a chemical sensing and response for muscular inflammation. Exercise as a stressor and as a generator of eccrine sweat causes “micro-tears” in the sarcomeres. Stressed skeletal muscles release glycoproteins, also known as cytokines, into the tissues and bloodstream from moderate and intense exercise or exertion. There are many glycoprotein messengers, yet this post addressed one pro-inflammatory sensing cytokine, called IL-6 or C-6.  Then we consider a responsive anti-inflammatory cytokine, IL-10 or C-10.

Recall that no two clients are identical for sweat functions; Fitter clients can work harder, thereby generating more heat to be cooled by eccrine sweat, likewise, a fit client with a genetic predetermination for less sweat may demonstrate such.

Sensory C-6 Cytokines are bodily messengers which alert our central nervous system (CNS) to that exercise-induced inflammation. Our bodies’ C-10 Cytokines respond to help that muscle or body region heal and restore. Note: Delayed onset of muscle soreness (DOMS) may also be a time-late indicator of adequate inflammation to induce muscle repair and restoration.

How does a client know what level of exertion or duration is adequate for this desirable sense-and-respond cycle?  There are estimates of exercise intensity in near real-time, then in non real-time measures or estimates after exercise is completed with “biomarkers”.

Case 1: A client’s stationary bicycle session includes blood checks for lactates vs. time and intensity of spinning. As a guideline, a blood lactate measurement of about 2 millimoles per liter (2 mmoL) indicates a “moderate intensity” threshold for aerobic exertion. If the cyclist exceeds that measured threshold at 4 or more minutes after a warm-up, anaerobic efforts should be adequate to generate DOMS and exercise-induced stress and sweat in a “survival” circuit, as Michael Sinclair labels it.

That survival circuit is a biochemical chain reaction that can promote a better fitness age, compared to a client’s calendar age. Now, many clients don’t care for the finger pricks and logistics of lactate testing. Relative Perceived Exertion (RPE) levels and monitored exercise heart rate are usual surrogates. When in doubt, if a client is just past the stage of conversational exercise, then the intensity is about right for the pro- and anti-inflammatory signaling to proceed.

Or, if that cyclist maintains a low/lower intensity spin for about 30 minutes or longer, that extended exertion should be sufficient to trigger exercise-induced stress and sweat that leads to biochemical sense and respond efforts for skeletal muscle repair and growth.

Added perks of sweat, or as ultra-athlete and author Christopher Bergland called “the biology of bliss” – like mood change and better sleep, were mentioned above when one sweats for a half hour or more of moderately intense exercise. After about 75-90 minutes of steady-state exercise, the cost-benefit of muscular and cardiovascular growth versus inflammation tapers off. As we know from both over-trained athletes, and from victims of COVID-19, inflammatory “cytokine storms” are counter-productive, or worse.

Case 2: A client’s resistance session includes a long, proper warmup before a focused program of high-intensity interval training, or HIIT.

The client’s HIIT efforts should feel vigorous and challenging, whether the session is for body weight or resistance training or including both. Respiration and training heart rate should be high – with the heart rates during intense exercise periods reaching 85-90% of maximum Heart Rate.

Sweat should be fairly heavy, and the client should not be able to converse. When this HIIT point or points occur, then the client has generated a bodily hypoxic response, which is a good temporal factor for activating bodily defenses versus aging without causing permanent harm. Note this credible finding which is echoed and endorsed by many exercise researchers,

“vigorous exercise has a clear advantage over moderate‐intensity exercise in inducing health‐related adaptations.”6

Safe Sweating – A Readiness Checklist

A four-point checkup for your client’s readiness for sweat and bliss is:

  • Am I adequately conditioned for my workout environment (altitude/dryness, temperature, shade from sun…)?

  • Have I acclimated to my workout environment with proper rest, nutrition and hydration?

  • Am I prepared to adapt my workout volume, intensity and tempo if conditions change?

  • Am I wearing anti-wicking clothing that is more comfortable and breathable for warm workout conditions or heavy exertion?


As Michael Sinclair asserts, DO SWEAT IT. Our clients need “the mild kind of adversity that wakes up and mobilizes cellular defenses without causing too much havoc.”

Take this to your client’s physical bank; exercise-induced sweat and stress, when appropriate in intensity or duration, can “turn on the genes to make us young again at the cellular level.


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[1] Citation Casa DJ, Cheuvront SN, Galloway SD, et al. Fluid needs for training, competition, and recovery in track-and-field athletesInt J Sport Nutr Exerc Metab. 2019;29(2):175–180.

[1a] Baker LB. Physiology of sweat gland function: The roles of sweating and sweat composition in human health. Temperature (Austin). 2019 Jul 17;6(3):211-259. doi: 10.1080/23328940.2019.1632145. PMID: 31608304; PMCID: PMC6773238.

[2] Sinclair, David, and Matthew D. LaPlante. Lifespan: Why We Age and Why We Don’t Have To. Harper Thorsons, 2021.

[3] Bergland, Christopher. The Athlete’s Way: Sweat and the Biology of Bliss. St. Martin’s Press, 2007.

[4] Jeukendrup, Asker, and Michael Gleeson. “Dehydration and Its Effects on Performance.”Humankinetics. N.p., n.d. Web. 17 July 2020,


[6] Nicolò A, Girardi M. The physiology of interval training: a new target to HIIT. J Physiol. 2016 Dec 15;594(24):7169-7170. doi: 10.1113/JP273466. PMID: 27976397; PMCID: PMC5157059.

Dave Frost

Dave Frost has served the fitness community as a NFPT-certified CPT since 2013, and a Master Fitness Trainer since 2019.
As a Medicare-aged baby boomer, he specializes in training those clients who intend to stay “well past forty”.
He is a former world champion in Masters Rowing and National Indoor Rowing champion for his age group. He is also a group fitness instructor for The Row House. His website is Dave recently published his work: KABOOMER: Thriving and Striving into your Nineties to promote stamininety for those intending to add years to their lives and life to their years.