Responses of muscle mass, strength and gene transcripts to long-term heat stress in healthy human subjects

Abstract

The present study was performed to investigate the effects of long-term heat stress on mass, strength and gene expression profile of human skeletal muscles without exercise training. Eight healthy men were subjected to 10-week application of heat stress, which was performed for the quadriceps muscles for 8 h/day and 4 days/week by using a heat- and steam-generating sheet. Maximum isometric force during knee extension of the heated leg significantly increased after heat stress (~5.8%, P < 0.05). Mean cross-sectional areas (CSAs) of vastus lateralis (VL, ~2.7%) and rectus femoris (~6.1%) muscles, as well as fiber CSA (8.3%) in VL, in the heated leg were also significantly increased (P < 0.05). Statistical analysis of microarrays (SAM) revealed that 10 weeks of heat stress increased the transcript level of 925 genes and decreased that of 1,300 genes, and gene function clustering analysis (Database for Annotation, Visualization and Integrated Discovery: DAVID) showed that these regulated transcripts stemmed from diverse functional categories. Transcript level of ubiquinol-cytochrome c reductase binding protein (UQCRB) was significantly increased by 10 weeks of heat stress (~3.0 folds). UQCRB is classified as one of the oxidative phosphorylation-associated genes, suggesting that heat stress can stimulate ATP synthesis. These results suggested that long-term application of heat stress could be effective in increasing the muscle strength associated with hypertrophy without exercise training.

Effects of Catechin-Ingestion and Heat Stress on the Maximum Isometric Force in Knee Extension, the Volume of Quadriceps Muscle, and Serum Thiobarbituric Acid Reactive Substances Level in Healthy Elderly Women

“…Previous study showed that 10-week of heat stress by using the same kind of heating sheet induces hypertrophy as well as increase of force generation of quadriceps muscle in healthy human subjects [16]. The discrepancy of the results from both studies may be due to the differences of heating area and subjects.…”

“…On the other hand, heat stress is one of hypertrophic stimuli for skeletal muscle [16,17]. It has been proposed that heat stress may be a countermeasure for prevention of muscle atrophy [18].…”

Intramuscular Heating Through Fluidotherapy and Heat Shock Protein Response

“…Goto et al 41 reported similar temperature increases to approximately 388C in the vastus lateralis during repeated bouts of heat treatment with a steam-generating sheet. As did Goto et al, 41 we found Fluidotherapy treatment resulted in an increase in peak temperature but did not produce an HSP response in the gastrocnemius or soleus muscle 24 hours posttreatment. Therefore, these data suggest that modalities capable of producing higher temperatures in shorter amounts of time or that render mechanical changes to the tissues should be used to induce HSP expression.…”

Effects of Nutritional Supplementation with Milk Fat Globule Membrane on Physical and Muscle Function in Healthy Adults Aged 60 and Over with Semiweekly Light Exercise: A Randomized Double-Blind, Placebo-Controlled Pilot Trial

“…Magnetic resonance imaging of each thigh was obtained by using a 1.5 T superconducting system (EXCELART Vantage 1.5T, Toshiba Medical Systems Co., Tokyo, Japan) to obtain the CSA of quadriceps muscles. The thigh image, obtained at 100 mm proximal to the knee joint, was utilized for calculation of the CSA by using a SCION image (19).…”