(51) ACUTE EFFECTS OF HIGH-INTENSITY ECCENTRIC EXERCISE ON STRENGTH, SORENESS, AND COLLAGEN BIOMARKERS

Purpose: Following eccentric exercise, there is typically a reduction in strength accompanied by an increase in muscle soreness and collagen degradation, however, the acute effects on collagen synthesis remain unknown. Therefore, the purpose of this study was to examine the effects of high-intensity eccentric exercise on strength, muscle soreness, and blood biomarkers of collagen degradation (hydroxyproline, HYP and c-terminal telopeptide of type I collagen, C1M) and synthesis (pro-c1α1 and procollagen type I N-terminal propeptide, PINP).

Methods: Ten men (mean±SD: age=21.8±2.3 yrs; body mass=81.0±9.3 kg; hheight=182.3±5.9 cm) completed a fasted baseline blood draw, a pre-exercise maximum voluntary isometric contraction (MVIC) and rating of muscle soreness (0-10 scale) followed by 5 sets of 10 eccentric muscle actions of the leg extensors at a load of 110% of their concentric 1RM, at a pace of 3 seconds per contraction. A post-exercise MVIC and rating of muscle soreness was obtained immediately after the last set. MVIC and ratings of muscle soreness were also obtained 24, 48, and 72 hours following the eccentric exercise, with a follow-up fasted blood draw at 48 hours. One-way RM ANOVAs with follow-up planned pairwise comparisons were used to analyze mean changes in MVIC and muscle soreness across time. Paired samples t-tests were used to examine mean changes in each blood biomarker.

Results: The one-way ANOVA indicated no significant (p=0.062) changes in MVIC, however, planned pairwise comparisons revealed a significant reduction in strength immediately after (437.0±77.2 to 387.4±67.3 n·m; p< 0.001, d=0.69) the eccentric exercise. The MVIC was recovered (p > 0.05) at 24 (429.6±83.7 n·m), 48 (413.7±65.9 n·m), and 72 hours (412.2±86.8 n·m) after the eccentric exercise. Ratings of muscle soreness significantly increased immediately (1.4±0.70 to 6.4±1.8; p< 0.001, d=3.70) after the eccentric exercise, and remained elevated 24 (3.7±1.6; p< 0.001, d=1.90), 48 (2.4±1.5; p=0.02, d=0.85), and 72 hours (2.3±1.2; p=0.03, d=0.94) after the eccentric exercise. For collagen degradation, there was no significant change in HYP (10.1±5.6 to 12.0±6.8 μg·mL^-1; p=0.49), but a significant mean increase (p=0.03, d=0.82) in C1M from baseline (5.9±1.8 μg·L^-1) to 48 hours (8.2±3.6 μg·L^-1). For collagen synthesis, there was no significant change in PINP (42.7±71.0 to 21.3±37.1 ng·mL^-1; p=0.28), but a significant mean decrease (p=0.01, d=0.43) in pro-c1α1 from baseline (59.8±41.6 ng·mL^-1) to 48 hours (43.5±34.5 ng·mL^-1).

Conclusion: The results of this study indicated that eccentric exercise caused an immediate reduction in MVIC with an accompanying increase in muscle soreness. Although MVIC recovered to pre-exercise values 24 hours after the eccentric exercise, muscle soreness remained elevated across 72 hours. These results indicated that muscle strength can be independent of muscle soreness. In addition, C1M was sensitive to increases in collagen degradation, however, HYP was not. Furthermore, pro-c1α1 was sensitive to decreases in collagen synthesis, while PINP was not.

Practical applications: The results of the current study provide researchers and clinicians with information regarding biomarkers sensitive to changes in collagen degradation and synthesis following high-intensity eccentric exercise. In addition, there can be a dissociation between muscle soreness and strength following high-intensity exercise.

Acknowledgements: None