Abstract
PurposeEvidence on training-induced muscle hypertrophy during preadolescence is limited and inconsistent. Possible associations of muscle strength and tendon stiffness with jumping performance are also not investigated. We investigated the thickness and pennation angle of the gastrocnemius medialis muscle (GM), as indicators for potential muscle hypertrophy in preadolescent athletes. Further, we examined the association of triceps surae muscle–tendon properties with jumping performance.MethodsEleven untrained children (9 years) and 21 similar-aged artistic gymnastic athletes participated in the study. Muscle thickness and pennation angle of the GM were measured at rest and muscle strength of the plantar flexors and Achilles tendon stiffness during maximum isometric contractions. Jumping height in squat (SJ) and countermovement jumps (CMJ) was examined using a force plate. We evaluated the influence of normalised muscle strength and tendon stiffness on jumping performance with a linear regression model.ResultsMuscle thickness and pennation angle did not differ significantly between athletes and non-athletes. In athletes, muscle strength was greater by 25% and jumping heights by 36% (SJ) and 43% (CMJ), but Achilles tendon stiffness did not differ between the two groups. The significant predictor for both jump heights was tendon stiffness in athletes and normalised muscle strength for the CMJ height in non-athletes.ConclusionLong-term artistic gymnastics training during preadolescence seems to be associated with increased muscle strength and jumping performance but not with training-induced muscle hypertrophy or altered tendon stiffness in the plantar flexors. Athletes benefit more from tendon stiffness and non-athletes more from muscle strength for increased jumping performance.
Highlights
Regular athletic training loads the musculoskeletal system and initiates adaptation in muscles (Folland and Williams 2007; Andersen and Aagaard 2010), tendons1 3 Vol.:(0123456789)European Journal of Applied Physiology (2020) 120:2715–2727(Arampatzis et al 2007a; Couppé et al 2008) and bones (Bennell et al 1997; Bass et al 2002)
The countermovement jumps (CMJ) height was 1.87 cm and 0.53 cm greater than in squat jumps (SJ) in athletes and nonathletes, respectively, but without any statistically significant differences between the two groups (d = 0.543, p = 0.155). Both maximum and normalised ankle joint moments were significantly greater in athletes (d = 1.33, p = 0.001; d = 1.4, p = 0.001, respectively; Table 2), but the Achilles tendon stiffness did not differ significantly between the two groups (d = 0.36, p = 0.341; Table 2)
There were no significant differences between the two groups in pennation angle of the gastrocnemius medialis muscle (GM) (d = 0.06, p = 0.895) and muscle thickness (d = 0.11, p = 0.764; Table 2)
Summary
Regular athletic training loads the musculoskeletal system and initiates adaptation in muscles (Folland and Williams 2007; Andersen and Aagaard 2010), tendons1 3 Vol.:(0123456789)European Journal of Applied Physiology (2020) 120:2715–2727(Arampatzis et al 2007a; Couppé et al 2008) and bones (Bennell et al 1997; Bass et al 2002). Regular athletic training loads the musculoskeletal system and initiates adaptation in muscles (Folland and Williams 2007; Andersen and Aagaard 2010), tendons. Due to substantial changes in muscle-anabolic hormones (Round et al 1999; Vingren et al 2010) from early to late adolescence, muscle strength increases rapidly with a similar development in the muscle size (Kanehisa et al 1995a, b). With the basal level of anabolic sex hormones being low (Round et al 1999; Murray and Clayton 2013) and the endocrine glands likely less responsive to exercise loading (Vingren et al 2010), the potential effects of exercise on muscle hypertrophy seem limited (Lloyd and Oliver 2012). The responsible mechanisms for the observed gains in muscle strength are not well explored, and it is often suggested that training-induced muscle strength gains before puberty be more related to neural adaptations, which include changes in motor unit coordination, rate coding and recruitment, rather than muscle hypertrophy (Faigenbaum et al 2009b)
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