Eccentric exercise before a 90min exposure at 24,000ft increases decompression strain depending on body region but not total muscle mass recruited.

Abstract

Eccentric upper-body exercise performed 24h prior to high-altitude decompression has previously been shown to aggravate venous gas emboli (VGE) load. Yet, it is unclear whether increasing the muscle mass recruited (i.e., upper vs. whole-body) during eccentric exercise would exacerbate the decompression strain. Accordingly, this study aimed to investigate whether the total muscle mass recruited during eccentric exercise influences the decompression strain. Eleven male participants were exposed to a simulated altitude of 24,000ft for 90min on three separate occasions. Twenty-four hours before each exposure, participants performed one of the following protocols: (i) eccentric whole-body exercise (ECCw; squats and arm-cycling exercise), (ii) eccentric upper-body exercise (ECCu; arm-cycling), or (iii) no exercise (control). Delayed onset muscle soreness (DOMS) and isometric strength were evaluated before and after each exercise intervention. VGE load was evaluated at rest and after knee- and arm-flex provocations using the 6-graded Eftedal-Brubakk scale. Knee extensor (-20±14%, P=0.001) but not elbow flexor (-12±18%, P=0.152) isometric strength was reduced 24h after ECCw. ECCu reduced elbow flexor isometric strength at 24h post-exercise (-18±10%, P<0.001). Elbow flexor DOMS was higher in the ECCu (median 6) compared with ECCw (5, P=0.035). VGE scores were higher following arm-flex provocations in the ECCu (median (range), 3 (0-4)) compared with ECCw (2 (0-3), P=0.039) and control (0 (0-2), P=0.011), and in ECCw compared with control (P=0.023). VGE were detected earlier in ECCu (13±20min) compared with control (60±38min, P=0.021), while no differences were noted between ECCw (18±30min) and control or ECCu. Eccentric exercise increased the decompression strain compared with control. The VGE load varied depending on the body region but not the total muscle mass recruited. HIGHLIGHTS: What is the central question of this study? Does exercise-induced muscle damage (EIMD) resulting from eccentric exercise influence the presence of venous gas emboli (VGE) during a 90min continuous exposure at 24,000ft? What is the main finding and its importance? EIMD led to an earlier manifestation and greater VGE load compared with control. However, the decompression strain was dependent on the body region but not the total muscle mass recruited.