Cotton vs polyester gym t-shirt across human trials and two reviews

Most trials comparing cotton with polyester during exercise found no meaningful difference in core temperature, heart rate or comfort ratings, and two reviews reach the same overall conclusion. For the cotton vs polyester gym t-shirt question, this guide sets out what controlled human trials and reviews actually measured, from rectal temperature and sweat retention to skin temperature, comfort and bacteria on worn shirts, so you can judge the marketing claims for yourself.

Key takeaways

• Most trials comparing cotton with polyester during exercise found no meaningful difference in core temperature, heart rate or comfort ratings, and two reviews reach the same overall conclusion.
• Where differences did appear, they mostly involved how much sweat stayed in the fabric, skin temperature, and how hot or exertion-heavy the session felt, though one cycling trial found a 0.8% faster 20-km time trial in a synthetic ensemble, and one found lower late-session rectal temperature with a form-fitted synthetic shirt.
• In the two trials whose abstracts report it, polyester or synthetic shirts retained less sweat than cotton ones. The two trials gave different core-temperature results (similar in Brazaitis et al.; lower late-session rectal temperature in De Sousa et al.), and neither measured performance.
• Blends, fabric construction and fit also shape comfort, so the fibre name on the label is only part of the picture.
• The evidence is limited: small groups, mostly men, mostly running, cycling and walking, and none of the studies summarised here tested lifting sessions specifically.

Why the material matters

Clothing can act as a barrier to evaporative and convective cooling during exercise in the heat (Davis and Bishop, 2013). A t-shirt sits between your skin and the air, so it can change how easily sweat evaporates and how the cloth feels against you. Two properties are often tested separately. Absorption is how much liquid a fabric takes up. Wicking, or water transfer, is how well it moves liquid along so it can evaporate (Dai et al., 2008). Synthetic sports fabrics are marketed as keeping wearers drier and cooler, and some are constructed with ventilation features such as mesh loops (Davis et al., 2017; Davis and Bishop, 2013).

That is the theory behind synthetic gym kit. The question for anyone weighing up a cotton vs polyester gym t-shirt is whether the theory shows up when real people exercise in real fabrics.

What the research says

Core temperature and heart rate: mostly no difference

Several trials measured core temperature as part of their heat-strain measures and found little separating the fabrics.

In a small study of eight well-trained men exercising at 30 °C and 35% relative humidity, an evaporative polyester ensemble, a traditional cotton ensemble and a swimsuit-only condition produced no differences in mean body, rectal or mean skin temperature during or after exercise, and no differences in oxygen use, heart rate or comfort. The only difference reported was a lower skin temperature in the swimsuit-only condition during pre-exercise rest (Gavin et al., 2001).

A later trial in eight male collegiate athletes compared 100% cotton, a 50/50 cotton and soybean blend and 100% polyester with mesh loops during a 45-minute run at 60% of maximal oxygen uptake at 32 °C. Clothing had no effect on rectal, skin or body temperature, heart rate, in-session ratings of perceived exertion or comfort scores (Davis et al., 2017). Session ratings taken afterwards did differ; see Perception below.

A randomised crossover study of 20 well-trained and national-level athletes ran for 60 minutes at 70% of peak oxygen uptake at 35 °C and 30% relative humidity in four garments: a cotton t-shirt, a sweat-wicking t-shirt, a compression t-shirt and a t-shirt with aluminium dots inside. Running speed, physiological heat strain and perceptual responses did not differ significantly between garments (Ioannou et al., 2024).

Where differences did appear

Not every study came up empty.

Ten men exercised for 45 minutes at 50% of peak oxygen uptake in 33 °C and 60% humidity, wearing either a 100% cotton short-sleeved shirt or a synthetic shirt made of 81% polyester and 19% elastane. Rectal temperature was lower in the synthetic condition during the last 15 minutes, and the synthetic shirt retained less sweat (De Sousa et al., 2014). The abstract describes the synthetic shirt as form fitted and does not say how the cotton shirt was cut, so fabric and cut may not have been separated.

In a 10 km outdoor run with six men and six women, heart rate, rectal and skin temperatures and pace did not differ among conditions, but a physiological strain index (PSI) was higher in the black and white cotton conditions than in the black and white polyester ones, and the black cotton shirt reached a higher shirt temperature than the white polyester, black polyester and white cotton shirts (Alcantara Borba et al., 2016).

In a 20-km cycling time trial with 15 competitive cyclists and triathletes at about 24 °C and 17% humidity with a simulated breeze, a synthetic ensemble (60% polyester and 40% nylon) beat a 100% cotton one by 15.7 seconds, or 0.8%. Mean skin temperature was about 1 °C lower, and comfort and thermal sensation ratings were more favourable. Core (oesophageal) temperature, sweat rate and perceived exertion did not explain the gain (Ferguson et al., 2021). Both outfits were loose-fitting long-sleeved mesh garments with trousers, so this is not a plain t-shirt comparison.

Sweat retention and skin temperature

In the two trials whose abstracts report how much sweat stayed in the shirt, the finding pointed the same way. In eight men running at 8 km/h in three 20-minute bouts at 25 °C and 60% humidity, a long-sleeve polyester shirt showed greater sweating efficiency and less clothing regain, meaning less sweat held in the garment, than cotton. Thermophysiological and subjective sensations during exercise were similar, but afterwards skin temperature returned to its pre-exercise level faster, and ratings of thermal and shivering or sweating sensation were lower with polyester (Brazaitis et al., 2010).

In a pilot trial of seven physically active men with obesity, 30 minutes of walking at 27 °C and 12% humidity in polyester or cotton shirts produced one fabric-by-time difference. The only fabric-by-time interaction was for forehead temperature (P = 0.016), though the abstract's figures are inconsistent, so treat the direction with caution. Perspiration rate did not differ, and the authors saw no superiority of either fabric (Masoud et al., 2023).

Perception: how hot and hard it feels

In the collegiate-athlete trial, the polyester ensemble with mesh loops lowered chest microenvironment temperature compared with cotton and reduced session ratings of exertion and thermal sensation, even though rectal temperature and heart rate were unchanged (Davis et al., 2017).

In the 20-athlete trial, runners reported larger areas of perceived suboptimal cooling in the cotton shirt and the aluminium-dot shirt than in the sweat-wicking and compression shirts (effect sizes 0.43 to 0.52), although the abstract reports no significant differences in perceptual responses, running speed or heat strain (Ioannou et al., 2024).

Blends and other fibres

The abstract of the collegiate trial reports no significant difference for the cotton/soybean blend on session exertion, thermal sensation or the other microenvironment areas it measured (the significant chest result was for the polyester ensemble versus cotton) (Davis et al., 2017). A separate wear trial found that a soybean protein and cotton blend with better wicking delayed and limited the rise in vapour pressure under the shirt and kept skin temperature beneath it lower than plain cotton (Dai et al., 2008).

Fibres can also behave differently once you stop. Twelve men cycled at 15 °C and 50% humidity, followed by a drying phase in a windy environment, wearing full-sleeve shirts. A wool shirt held greater torso skin temperature than cotton, viscose or polyester, and was rated more comfortable afterwards (Abedin and DenHartog, 2024). That is a cool-conditions result, but it shows the cotton-versus-polyester framing can leave out options.

Odour and bacteria on worn shirts

Ten students wore polyester, cotton and polyester-cotton shirts during exercise, and the shirts were sampled using 16S rRNA gene sequencing. Overall bacterial diversity did not differ between the three fabrics. Pantoea and Pseudomonas, which mainly come from the environment, were enriched on polyester but not cotton, while Enhydrobacter, which comes from human skin, did better on cotton, with the blend in between (Yan et al., 2022). The abstract does not measure odour, so the study cannot tell us which shirt smells worse.

What the reviews conclude

A 2022 narrative review of sports clothing in the heat found that few studies have identified significant differences between natural and synthetic fabrics in thermo-physiological, perceptual or performance measures. It called for tests in hot, humid conditions (30 °C or more and 70% humidity or more), sessions longer than 45 minutes, and richer measures of comfort (Di Domenico et al., 2022).

A 2013 review reached a similar view: the majority of research on advertised synthetic fabrics showed no difference in thermoregulation or comfort against natural fabrics in the heat, and clothing construction has been little studied (Davis and Bishop, 2013).

What this means when choosing

None of this makes either fabric a clear winner. These are general patterns, not promises.

• Think about the whole picture, not just the fibre. Three trials at 30-35 °C (Gavin et al., 2001; Davis et al., 2017; Ioannou et al., 2024) found no difference in core or rectal temperature between fabrics (Ioannou et al. also found no difference in running speed), but De Sousa et al. (2014), at 33 °C, found lower late-session rectal temperature with a form-fitted synthetic shirt. The trials that found synthetic advantages differed in conditions, garments and measures, so they do not point to a clear threshold at which fibre starts to matter.
• Cotton shirts held more sweat in the two trials whose abstracts report it. In 8 men running in long-sleeve shirts (Brazaitis et al., 2010) and 10 men in a form-fitted polyester-elastane shirt (De Sousa et al., 2014), the cotton shirt retained more sweat. Both samples were small and all-male, so treat this as a pattern, not a promise.
• Pay attention to fit and construction. A manikin study found that a flared, fuller cut reduced a t-shirt’s thermal insulation and moisture vapour resistance when walking or in wind, and small openings helped further (Ho et al., 2011). That was a manikin test of one flared design, not people wearing fitted or relaxed tees, so it does not show that a larger size would feel cooler. Fabric is not the only variable.
• Treat comfort as personal. Many trials found no difference in comfort ratings, so the shirt you will actually wear is a reasonable tie-breaker.

If you are comparing options, the practical question behind a cotton vs polyester gym t-shirt choice is often fit, feel and how you train, rather than a single fibre label. A cotton gym t-shirt in an athletic cut is one example; see the product section below for what its page does and does not say.

Limits of the evidence

• Small samples. The human trials above that reported sample sizes used between 7 and 20 participants, mostly men; one study used a manikin. Results may not carry over to everyone.
• Short sessions and narrow activities. The studies covered walking, running and cycling. Where the abstracts give a duration, exercise lasted from 30 to 60 minutes (Brazaitis used three 20-minute bouts); the 10 km run and 20 km time trial durations are not stated. None of the studies summarised here tested heavy resistance training.
• Conditions vary widely. Temperatures ranged from 15 °C to 35 °C and humidity from 12% to 60% across the trials. The 2022 review argued that hot and humid protocols and longer sessions are still needed (Di Domenico et al., 2022).
• Odour, shrinkage and print wear are untested here. The bacterial study did not measure smell, and none of the sources reviewed here covered shrinkage or print wear.

The Free Muscle product in this context

The Free Muscle T-Shirt is a cotton gym tee. Its product page describes it as an athletic cut, tapered through the body and shoulders, with a soft, breathable cotton feel, a Free Muscle graphic and reinforced stitching. It comes in five sizes, XS to XL. The page advises sizing up for a relaxed fit, and care instructions are to machine wash cold, inside out, and hang to dry to protect the print.

Read against the research above, two points matter. The page does not give a fabric weight or an exact cotton percentage, and states no polyester or elastane content, so we cannot say how this shirt would compare in the trials described. The studies also tested other garments, so they are general context rather than evidence about this tee.

If you want to see the wider range of apparel, browse the Free Muscle merch collection.

Frequently asked questions

What did the trials measure in the cotton vs polyester gym t-shirt comparison?

Across the human trials summarised here, the measures included core or rectal temperature, heart rate, sweat retained in the shirt, skin temperature, comfort and perceived exertion, and, in one study, bacteria on worn shirts. Most found no meaningful difference in core temperature, heart rate or comfort, and two reviews reach the same overall conclusion (Di Domenico et al., 2022; Davis and Bishop, 2013).

Is cotton bad for the gym?

The research shows no clear disadvantage in most trials, and two reviews reach the same overall conclusion (Di Domenico et al., 2022; Davis and Bishop, 2013). A few trials found cotton held more sweat or felt less cooling, and none of the studies summarised here tested lifting sessions.

Is polyester better than cotton for the gym?

The research does not give a simple yes. Several trials found no differences in core temperature, heart rate or comfort (Gavin et al., 2001; Davis et al., 2017; Ioannou et al., 2024), while two trials found advantages for synthetic shirts, a lower late-session rectal temperature (De Sousa et al., 2014) and a 0.8% faster 20-km cycling time trial (Ferguson et al., 2021).

Does cotton hold more sweat than polyester?

In the two small all-male trials whose abstracts report it, the cotton shirt retained more sweat (Brazaitis et al., 2010; De Sousa et al., 2014). The trials did not agree on whether that changes core temperature. Sweat rate itself did not differ in the walking trial in seven men with obesity (Masoud et al., 2023).

What do the studies say about blends?

No trial in our sources compared a cotton-polyester blend on heat or comfort. Two trials tested a cotton-soybean blend: Dai et al. (2008) found it kept vapour pressure and skin temperature under the shirt lower than cotton in a wear trial, while Davis et al. (2017) found no significant difference for the blend on session exertion or thermal sensation. The only cotton-polyester blend study measured bacteria: the abstract reports the blend as intermediate between polyester and cotton for Enhydrobacter, a genus from human skin, with no overall diversity difference between the three fabrics (Yan et al., 2022).

Does shirt colour matter when exercising?

In the 10 km outdoor trial, pace did not differ by colour or fabric, but the black cotton shirt reached a higher shirt temperature than the other shirts tested (Alcantara Borba et al., 2016).

Do polyester shirts smell worse than cotton?

We cannot say from the research reviewed. The only study among those reviewed that sampled bacteria on shirts after exercise found no overall diversity difference between polyester, cotton and polyester-cotton shirts, though a few genera, such as Pantoea and Pseudomonas on polyester and Enhydrobacter on cotton, were more common on one fabric, and it did not measure smell (Yan et al., 2022).

Does the cut of a t-shirt change heat and moisture transfer?

A thermal manikin study found that a fuller, flared cut lowered thermal insulation and moisture vapour resistance when walking or in wind compared with traditionally sized shirts (Ho et al., 2011). The caveat in the bullet above applies: it was a manikin test of one flared design.

Sources

1. Masoud AA, Alansare AB, Finch AE. Physiological effects of exercise in heat while wearing a polyester versus cotton T-shirt in physically active men with obesity: a pilot study. J Sports Med Phys Fitness. 2023;63(12):1358-1365. doi:10.23736/S0022-4707.23.15164-4. PMID 37721720
2. De Alcantara Borba D, Ferreira JB, Coelho LG, et al. T-Shirt fabric and color affect the physiological strain but not 10 km outdoor running performance. J Sports Med Phys Fitness. 2016;56(4):359-67. PMID 25567048
3. De Sousa J, Cheatham C, Wittbrodt M. The effects of a moisture-wicking fabric shirt on the physiological and perceptual responses during acute exercise in the heat. Appl Ergon. 2014;45(6):1447-53. doi:10.1016/j.apergo.2014.04.006. PMID 24768089
4. Brazaitis M, Kamandulis S, Skurvydas A, Daniusevičiūtė L. The effect of two kinds of T-shirts on physiological and psychological thermal responses during exercise and recovery. Appl Ergon. 2010;42(1):46-51. doi:10.1016/j.apergo.2010.04.001. PMID 20427033
5. Gavin TP, Babington JP, Harms CA, et al. Clothing fabric does not affect thermoregulation during exercise in moderate heat. Med Sci Sports Exerc. 2001;33(12):2124-30. doi:10.1097/00005768-200112000-00023. PMID 11740309
6. Davis JK, Laurent CM, Allen KE, et al. Influence of clothing on thermoregulation and comfort during exercise in the heat. J Strength Cond Res. 2017;31(12):3435-3443. doi:10.1519/JSC.0000000000001754. PMID 27984496
7. Ioannou LG, Tsoutsoubi L, Gkiata P, et al. Effect of sportswear on performance and physiological heat strain during prolonged running in moderately hot conditions. Scand J Med Sci Sports. 2024;34(1):e14520. doi:10.1111/sms.14520. PMID 37839051
8. Ferguson J, Hadid A, Epstein Y, Jensen D. Effect of clothing fabric on 20-km cycling performance in endurance athletes. Front Sports Act Living. 2021;3:735923. doi:10.3389/fspor.2021.735923. PMID 35072062
9. Di Domenico I, Hoffmann SM, Collins PK. The role of sports clothing in thermoregulation, comfort, and performance during exercise in the heat: a narrative review. Sports Med Open. 2022;8(1):58. doi:10.1186/s40798-022-00449-4. PMID 35482166
10. Davis JK, Bishop PA. Impact of clothing on exercise in the heat. Sports Med. 2013;43(8):695-706. doi:10.1007/s40279-013-0047-8. PMID 23620245
11. Abedin F, DenHartog E. Clothing impact on post-exercise comfort: skin-clothing physiology in transient environment. Ergonomics. 2024;67(8):1080-1096. doi:10.1080/00140139.2023.2281272. PMID 37960939
12. Ho C, Fan J, Newton E, Au R. The effect of added fullness and ventilation holes in T-shirt design on thermal comfort. Ergonomics. 2011;54(4):403-10. doi:10.1080/00140139.2011.556260. PMID 21491282
13. Dai XQ, Imamura R, Liu GL, Zhou FP. Effect of moisture transport on microclimate under T-shirts. Eur J Appl Physiol. 2008;104(2):337-40. doi:10.1007/s00421-007-0628-z. PMID 18071744
14. Yan H, Ren Y, Zhou B, Ye F, Wu Z. Microbial profile of T-shirts after a fitness session of Chinese students. Heliyon. 2022;8(12):e12379. doi:10.1016/j.heliyon.2022.e12379. PMID 36582726