Triceps Surae Muscle-Tendon Unit Properties in Preadolescent Children: A Comparison of Artistic Gymnastic Athletes and Non-athletes

Abstract

Knowledge regarding the effects of athletic training on the properties of muscle and tendon in preadolescent children is scarce. The current study compared Achilles tendon stiffness, plantar flexor muscle strength and vertical jumping performance of preadolescent athletes and non-athletes to provide insight into the potential effects of systematic athletic training. Twenty-one preadolescent artistic gymnastic athletes (9.2 ± 1.6 years, 15 girls) and 11 similar-aged non-athlete controls (9.0 ± 1.7 years, 6 girls) participated in the study. The training intensity and volume of the athletes was documented for the last 6 months before the measurements. Subsequently, vertical ground reaction forces were measured with a force plate to assess jumping performance during squat (SJ) and countermovement jumps (CMJ) in both groups. Muscle strength of the plantar flexor muscles and Achilles tendon stiffness were examined using ultrasound, electromyography, and dynamometry. The athletes trained 6 days per week with a total of 20 h of training per week. Athletes generated significantly greater plantar flexion moments normalized to body mass compared to non-athletes (1.75 ± 0.32 Nm/kg vs. 1.31 ± 0.33 Nm/kg; p = 0.001) and achieved a significantly greater jump height in both types of jumps (21.2 ± 3.62 cm vs. 14.9 ± 2.32 cm; p < 0.001 in SJ and 23.4 ± 4.1 cm vs. 16.4 ± 4.1 cm; p < 0.001 in CMJ). Achilles tendon stiffness did not show any statistically significant differences ( p = 0.413) between athletes (116.3 ± 32.5 N/mm) and non-athletes (106.4 ± 32.8 N/mm). Athletes were more likely to reach strain magnitudes close to or higher than 8.5% strain compared to non-athletes (frequency: 24% vs. 9%) indicating an increased mechanical demand for the tendon. Although normalized muscle strength and jumping performance were greater in athletes, gymnastic-specific training in preadolescence did not cause a significant adaptation of Achilles tendon stiffness. The potential contribution of the high mechanical demand for the tendon to the increasing risk of tendon overuse call for the implementation of specific exercises in the athletic training of preadolescent athletes that increase tendon stiffness and support a balanced adaptation within the muscle-tendon unit.

Individualized Muscle-Tendon Assessment and Training

“…However, a significant relationship between muscle strength and tendon stiffness does not give evidence to a balanced adaptation within the MTU, because a high or low relationship does not provide any information concerning the margin of tolerated mechanical tendon loading during MVCs. There is experimental evidence of imbalances between muscle strength and tendon stiffness in competitive athletes from child- to adulthood due to different alterations of muscle and tendon properties, resulting in remarkably high or low tendon strain values ( Mersmann et al, 2016 ; Charcharis et al, 2019 ; Pentidis et al, 2019 ). Those imbalances indicate the relevance of an individualized training control and regulation.…”

Effects of long-term athletic training on muscle morphology and tendon stiffness in preadolescence: association with jump performance

“…The pubertal status of the participants was assessed by their parents, by determining the Tanner stage according to drawings of the respective features Tanner 1969, 1970). At the time of data acquisition, the training intensity and volume of the athletes had been documented for the last 6 months and averaged to ∼ 5 h of specific muscle strength and jumping training and ∼ 12 h of main on-apparatus gymnastic training per week, including plyometric and landing exercises (for a detailed description of the training see Pentidis et al 2019).…”

“…Therefore, we can argue that additional investigations examining the effects of systematic resistance training on muscle hypertrophy in preadolescence are needed to better understand musculotendinous adaptive responses in this age. The athletic training in artistic gymnastics is characterised by a high volume of exercises requiring a high level of muscle strength exertion like jumping, landing, and movements on the apparatus in the age before puberty (Pentidis et al 2019), and is, therefore, appropriate for the investigation of possible training-induced hypertrophy in preadolescence.…”

The effects of growth on structural properties of the Achilles and Patellar tendons: A cross‐sectional study

“…Although it has been attempted previously to investigate the growth changes in structural properties (length and cross-sectional area) of tendons (Kubo, Teshima, Hirose, & Tsunoda, 2014a, 2014bO'Brien, Reeves, Baltzopoulos, Jones, & Maganaris, 2010;Neugebauer & Hawkins, 2012;Mersmann et al, 2014Mersmann et al, , 2017Mogi et al, 2018;Waugh, Blazevich, Fath, & Korff, 2012. ), however, there is few information on the structural properties of the tendons at and/or around adolescent growth spurt (Charcharis, Mersmann, Bohm, & Arampatzis, 2019;Mogi et al, 2018;Mogi, 2019;Pentidis et al, 2019), and no studies have simultaneously examined the structural properties of both the Patellar and Achilles tendons at around adolescent growth spurt. have demonstrated that cross-sectional area of the Achilles tendon in distal region was greater than that of proximal region, and stated that region-specific hypertrophy in cross-sectional area of tendon occurs in response to the habitual loading.…”