Daily deep heating slowed muscle loss in legs held still for 10 days
In this 2019 Journal of Applied Physiology study, 23 healthy adults had one leg immobilized for 10 days. Each day their thigh got two hours of shortwave heating or a sham treatment.
The paper
Daily heat treatment maintains mitochondrial function and attenuates atrophy in human skeletal muscle subjected to immobilization
Hafen PS, Abbott K, Bowden J, Lopiano R, et al.. Journal of Applied Physiology, 2019;127(1):47-57.
See the study at a glance
- Design
- Controlled trial of heat against sham
- People
- 23 healthy adults
- Who they were
- Eleven healthy women and 12 healthy men.
- What they did
- One leg stayed immobilized for 10 days. Each day the outer thigh muscle got two hours of either pulsed shortwave diathermy (deep heating with radio waves) or a sham. The heat raised muscle temperature by 4.2°C.
- How long
- 10 days
These numbers came out of it
−4.5%
The whole muscle's cross-sectional area (a measure of its size) shrank 4.5% with daily heat. With sham it shrank 7.6%.
−5.8%
Individual muscle fibers shrank 5.8% in cross-sectional area with heat and 10.8% with sham.
−8%
Coupled respiration, which measures how well the muscle's mitochondria make energy, fell 8% with heat and 27% with sham.
+25%
Heat shock protein 70 rose 25% in the heated muscle, and HSP90 rose 20%.
The researchers did this
Twenty-three healthy adults had one leg immobilized for 10 days. Every day a pulsed shortwave diathermy device heated the outer thigh muscle for two hours, or a sham device went through the motions.Source 1 · Clinical trialDaily heat treatment maintains mitochondrial function and attenuates atrophy in human skeletal muscle subjected to immobilizationHafen PS, Abbott K, Bowden J, et al.. Journal of Applied Physiology, 2019.Read the paper ↗PubMed ↗ The heat raised muscle temperature by 4.2°C.
Both groups lost muscle, and the heated group lost less. The whole muscle's cross-sectional area fell 7.6% with sham and 4.5% with heat. Measured fiber by fiber, the loss came to 10.8% with sham and 5.8% with heat.
The mitochondria fared better too. Their coupled respiration fell 27% with sham and 8% with heat. In the heated muscle, heat shock protein 70 rose 25% and HSP90 rose 20%.
A sauna warms muscle less than this. In one study, 40 minutes at 80°C raised muscle temperature by 1.95°C, and the diathermy here produced more than twice that.Source 2 · Clinical trialThe vascular response to acute sauna heating is similar in young and middle-aged adultsLeach OK, Strong K, Mack GW, et al.. Journal of Applied Physiology, 2024.Read the paper ↗PubMed ↗
The study can't tell you these things
- The heat came from a diathermy device aimed at one muscle for two hours a day. A sauna heats the whole body for minutes and warms muscle less.Source 2 · Clinical trialThe vascular response to acute sauna heating is similar in young and middle-aged adultsLeach OK, Strong K, Mack GW, et al.. Journal of Applied Physiology, 2024.Read the paper ↗PubMed ↗
- The abstract doesn't say how people ended up in the heat or sham group.
- The volunteers were healthy and immobilized for only 10 days, so the study can't speak to muscle loss after surgery or during illness.
- The study measured how much muscle people lost while a leg was out of use. Whether heat helps people who train build muscle is a separate question it didn't test.
We cited these sources
- 01Hafen PS, Abbott K, Bowden J, Lopiano R, Hancock CR, Hyldahl RD. Daily heat treatment maintains mitochondrial function and attenuates atrophy in human skeletal muscle subjected to immobilization. Journal of Applied Physiology. 2019;127(1):47-57. doi:10.1152/japplphysiol.01098.2018 PMID 31046520
- 02Leach OK, Strong K, Mack GW, Gifford JR. The vascular response to acute sauna heating is similar in young and middle-aged adults. Journal of Applied Physiology. 2024;136(3):573-582. doi:10.1152/japplphysiol.00287.2023 PMID 38271083