Your Muscles Like it Hot

Two weeks ago, we posted a news article about a new study showing that postexercise cooling can harm your gains. Today, let’s take a look at another study, this one examining the other side of the temperature scale, heat. Heat applied to the muscles, more precisely, and the fact that this procedure seems to be beneficial and help muscle growth.

Thirty young and healthy males performed 18 training sessions over the course of 6 weeks. They trained 3 times per week, performing 3 sets of 8 repetitions of lying dumbbell triceps extensions each workout. The intensity of the workouts was very low. The participants only used a load corresponding to 30% of their 1RM, and stopped at 8 reps. Very light, non-failure training, in other words.

Half of the subjects acted as a control group and trained normally. The other half, the intervention group, applied a heat pack to the muscle before each training session. The heat pack was heated to 75 °C in an hydrocollator and wrapped in a towel, then held against the muscle belly of the triceps for 20 minutes.


No changes in strength or muscle thickness were evident in the control group after 6 weeks of training. Not surprising. This super-low intensity is not enough for any kind of gains, regardless of training experience.

The men who applied the hot pack to the muscle before training it, on the other hand, experienced significant increases in muscle strength and muscle thickness, as measured by ultrasonography, from the same low-volume, low-intensity training.

muscles like it hot

The study did not try to investigate the mechanisms behind these gains. However, previous research suggests that heat applied to muscles can increase anabolic signaling.

It is important to keep in mind that this is a pilot study. The results need replication and confirmation. If that happens, this could be applied to, for example, situations where an athlete can’t train hard and heavy, like during an injury, or in the frail and elderly.

If nothing else, the results from this study, combined with what we know about the effects of cold on muscle growth, suggest that your muscles like it hot.


BMC Musculoskeletal Disorders volume 20, Article number: 603 (2019). The effect of low-intensity resistance training after heat stress on muscle size and strength of triceps brachii: a randomized controlled trial.

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Andreas Abelsson

Andreas is a certified nutrition coach with over three decades of training experience. He has followed and reported on the research fields of exercise, nutrition, and health for almost as long and is a specialist in metabolic health and nutrition coaching for athletes. Read more about Andreas and StrengthLog by clicking here.