Abstract
This study compared changes in indirect muscle damage markers, proprioception and arterial stiffness after elbow flexor eccentric exercise between pre-pubescent (9–10 y), pubescent (14–15 y), and post-pubescent (20–24 y) healthy, untrained females (n = 13/group). The maturation of the participants was confirmed by the hand bone age. All participants performed two bouts of 30 sub-maximal eccentric contractions (EC1, EC2) using a dumbbell set at 60% of pre-exercise maximal voluntary isometric elbow flexion strength at 90°. Changes in maximal voluntary concentric contraction (MVC) torque, muscle soreness (SOR), plasma creatine kinase activity, proprioception (position sense, joint reaction angle) and arterial stiffness (carotid-femoral pulse-wave velocity: cfPWV) before to 5 days after EC1 and EC2 were compared among groups by a mixed-design two-way ANOVA. Pre-exercise MVC torque and cfPWV were smaller (P < 0.05) for the pre-pubescent (MVC: 10.0 ± 0.9 Nm, cfPWV: 903 ± 60 cm/s) and the pubescent (14.3 ± 1.1 Nm, 967 ± 61 cm/s) than the post-pubescent (19.1 ± 1.4 Nm, 1,103 ± 73 cm/s). Changes in all variables after EC1 were smaller (P < 0.05) for the pre-pubescent (e.g., MVC at 1 d post-exercise: −10 ± 6%, peak SOR: 5 ± 2 mm) than the pubescent (−15 ± 9%, 12 ± 6 mm) and the post-pubescent (−25 ± 7%, 19 ± 13 mm). After EC2, changes in all variables were smaller (P < 0.05) than those after EC1 for all groups (e.g., MVC at 1 d post-exercise, pre-pubescent: −4 ± 6%, pubescent: −9 ± 4%, post-pubescent: −14 ± 5%; peak SOR: 3 ± 2, 7 ± 3, 11 ± 6 mm), but the magnitude of the repeated bout effect was not different (P > 0.05) among the groups. These results show that the extents of muscle damage, and proprioception and arterial stiffness changes after eccentric exercise are greater at later stages of maturation, but the repeated bout effect is not affected by maturation.
Highlights
Unaccustomed eccentric exercise induces muscle damage that is commonly indicated by prolonged decreases in muscle function, delayed onset muscle soreness (DOMS), and increased muscle proteins such as creatine kinase (CK) and myoglobin (Mb) in the blood (Hyldahl and Hubal, 2014; Goodall et al, 2017; Warren et al, 2017)
The present study showed that changes in muscle damage, proprioception and arterial stiffness measures following the first bout of eccentric exercise of the elbow flexors were significantly smaller for the pre-pubescent and pubescent groups than postpubescent group, and all changes except muscle passive stiffness were significantly smaller for the pre-pubescent than pubescent group (Figures 1–4)
The results of the current study showed that the extent of muscle damage, and its effects on proprioception and arterial stiffness changes after eccentric exercise of the elbow flexors were significantly smaller for pre-pubescent girls, followed by pubescent girls than women, but the magnitude of the repeated bout effect was similar among the groups
Summary
Unaccustomed eccentric exercise induces muscle damage that is commonly indicated by prolonged decreases in muscle function, delayed onset muscle soreness (DOMS), and increased muscle proteins such as creatine kinase (CK) and myoglobin (Mb) in the blood (Hyldahl and Hubal, 2014; Goodall et al, 2017; Warren et al, 2017). To the best of our knowledge, six studies have reported muscle damage in children in comparison to adults after either downhill running (Webber et al, 1989), bench press (Soares et al, 1996), plyometric jumps (Marginson et al, 2005; Gorianovas et al, 2013), or maximal isokinetic eccentric contractions of the elbow flexors (Chen et al, 2014) and knee extensors (Deli et al, 2017). All of these studies showed that muscle damage was less in children than in adults. Limited information is available for the effects of growth or maturation on muscle damage in females
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