The Effects of Heat Therapy During Immobilization and Rehabilitation on Muscle Atrophy and Strength Loss at Return to Sports in Healthy Humans.
Level 3 - non-randomized controlled study
Controlled trial with sham comparator; randomization is not explicitly stated in the abstract
PubMed 39444938 · doi:10.1177/23259671241281727
What was done
Twenty healthy men (age 33.6 ± 2.8 years) completed 4 weeks of supervised training, 2 weeks of unilateral lower leg immobilization, and 2 weeks of supervised rehabilitation before return to sports (RTS). Participants were split into two groups: whole-body heat therapy (HEAT) or sham treatment (SHAM) administered throughout immobilization and rehabilitation. Muscle strength (isometric and isokinetic), muscle architecture/volume (MRI and ultrasound), and muscle biopsies were assessed pre-immobilization, post-immobilization, and at RTS.
What was found
Maximal isometric plantarflexor strength decreased at RTS compared to pre-immobilization in SHAM (P = .027) but not in HEAT (P = .301). Isokinetic fatigue strength at RTS increased compared to pre-immobilization in HEAT (P = .039) but not in SHAM (P = .245). Pennation angle and muscle thickness decreased post-immobilization only in SHAM (P ≤ .027). Muscle cross-sectional area decreased across soleus, gastrocnemius medialis, and gastrocnemius lateralis in SHAM (all P ≤ .035), whereas in HEAT, only gastrocnemius medialis decreased. Biopsies showed increased phosphorylated FoxO in HEAT (P = .034), a non-significant decrease in phosphorylated/total NFκB ratio in HEAT (d = 0.91, P = .054), and increased caspase 3 expression post-immobilization in SHAM only (P = .004).
Why it matters
This study provides human evidence that whole-body heat therapy can mitigate immobilization-induced muscle atrophy and retain strength, likely through the downregulation of proteolytic signaling pathways (FoxO and caspase 3).
Limits
The study is limited by a small sample size (n = 20) restricted to healthy adult males. The abstract does not specify whether allocation was randomized or if outcome assessors were blinded. Exact baseline and post-intervention numerical values and confidence intervals for strength and morphological metrics were not provided in the abstract.
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