Effects of repeated use of post-exercise infrared sauna on neuromuscular performance and muscle hypertrophy

Abstract

Purpose: The aim of this study was to investigate whether regular use of infrared sauna (IRS) after training can promote neuromuscular performance and positive changes in body composition during a 6-week training period.

Methods: Forty female team sport athletes were pair-matched into two groups: IRS (n = 20) and control (CON; n = 20). Physical performance tests, body composition and hypertrophy measurements (dual-energy x-ray absorptiometry and ultrasound of m. vastus lateralis) were performed PRE and POST a 6-week strength and power training period, involving 2-3 sessions per week. Performance tests included a 20 m sprint, squat jump (SJ), countermovement jumps with body weight (CMJ) as well as with 15, 25, and 50% additional load (CMJ15%, CMJ25%, and CMJ50%), and a maximal isometric leg press (MVC). Participants in the IRS-group used IRS (10 min, 50℃) after training three times per week.

Results: Training improved neuromuscular performance and muscle hypertrophy in both groups (p < 0.05). Following the discovery of an interaction effect for CMJ15% height (p = 0.002) and peak power (p = 0.010), post hoc tests revealed higher jump height POST-IRS (p = 0.006) and PRE-CON (p = 0.023) compared to PRE-IRS, and higher peak power POST-IRS (p = 0.002) compared to PRE-IRS. Furthermore, an interaction effect was observed for 5 m split time of the 20 m sprint (p = 0.020), but no differences were found between groups and timepoints. There were no interactions for the hypertrophy measures.

Conclusion: Incorporating post-exercise IRS bathing does not significantly impact hypertrophy gains, but might boost long-term power production capabilities.

Keywords: female athletes; heat therapy; hypertrophy; physical performance; recovery; team-sport.

Figure 1

Mean and individual values of (A) 20 m sprint, (B) 5 m split time, and (C) isometric leg press (MVC). CON, control group; IRS, infrared sauna group; PRE, before the intervention; POST, after the intervention. # Indicates interaction effect between IRS and CON in GEE-model (p < 0.05).

Figure 2

Mean and individual values of jump test results. (A) squat jump (SJ) height, (B) squat jump (SJ) peak power, (C) countermovement jump (CMJ) height, (D) countermovement jump (CMJ) peak power, (E) countermovement jump with 15% additional load (CMJ15%) height, (F) countermovement jump with 15% additional load (CMJ15%) peak power, (G) countermovement jump with 25% additional load (CMJ25%) height, (H) countermovement jump with 25% additional load (CMJ25%) peak power, (I) countermovement jump with 50% additional load (CMJ50%) height, and (J) countermovement jump with 50% additional load (CMJ50%) peak power. CON, control group; IRS, infrared sauna group; PRE, before the intervention; POST, after the intervention. *Indicates differences in t-tests (p < 0.05); **indicates differences in t-tests (p < 0.01); # indicates interaction effect between IRS and CON in GEE-model (p < 0.05); ## indicates interaction effect between IRS and CON in GEE-model (p < 0.01), ¤ indicates time effect in GEE-model (p < 0.05), ¤¤ indicates time effect in GEE-model (p < 0.01).

Figure 3

Mean and individual values of (A) body mass, (B) fat mass, (C) lean mass, (D) lower body lean mass, (E) cross-sectional area of vastus lateralis, and (F) pennation angle of vastus lateralis. CON, control group; IRS, infrared sauna group; PRE, before the intervention; POST, after the intervention. *Indicates differences in t-tests (p < 0.05); **indicates differences in t-tests (p < 0.01); # indicates interaction effect between IRS and CON in GEE-model (p < 0.05), ¤¤ indicates time effect in GEE-model (p < 0.01), ¤¤¤ indicates time effect in GEE-model (p < 0.001).