Trunk Extensor and Flexor Strength Capacity in Healthy Young Elite Athletes Aged 11–15 Years

Abstract

Differences in trunk strength capacity because of gender and sports are well documented in adults. In contrast, data concerning young athletes are sparse. The purpose of this study was to assess the maximum trunk strength of adolescent athletes and to investigate differences between genders and age groups. A total of 520 young athletes were recruited. Finally, 377 (n = 233/144 M/F; 13 ± 1 years; 1.62 ± 0.11 m height; 51 ± 12 kg mass; training: 4.5 ± 2.6 years; training sessions/week: 4.3 ± 3.0; various sports) young athletes were included in the final data analysis. Furthermore, 5 age groups were differentiated (age groups: 11, 12, 13, 14, and 15 years; n = 90, 150, 42, 43, and 52, respectively). Maximum strength of trunk flexors (Flex) and extensors (Ext) was assessed in all subjects during isokinetic concentric measurements (60°·s(-1); 5 repetitions; range of motion: 55°). Maximum strength was characterized by absolute peak torque (Flexabs, Extabs; N·m), peak torque normalized to body weight (Flexnorm, Extnorm; N·m·kg(-1) BW), and Flexabs/Extabs ratio (RKquot). Descriptive data analysis (mean ± SD) was completed, followed by analysis of variance (α = 0.05; post hoc test [Tukey-Kramer]). Mean maximum strength for all athletes was 97 ± 34 N·m in Flexabs and 140 ± 50 N·m in Extabs (Flexnorm = 1.9 ± 0.3 N·m·kg(-1) BW, Extnorm = 2.8 ± 0.6 N·m·kg(-1) BW). Males showed statistically significant higher absolute and normalized values compared with females (p < 0.001). Flexabs and Extabs rose with increasing age almost 2-fold for males and females (Flexabs, Extabs: p < 0.001). Flexnorm and Extnorm increased with age for males (p < 0.001), however, not for females (Flexnorm: p = 0.26; Extnorm: p = 0.20). RKquot (mean ± SD: 0.71 ± 0.16) did not reveal any differences regarding age (p = 0.87) or gender (p = 0.43). In adolescent athletes, maximum trunk strength must be discussed in a gender- and age-specific context. The Flexabs/Extabs ratio revealed extensor dominance, which seems to be independent of age and gender. The values assessed may serve as a basis to evaluate and discuss trunk strength in athletes.

Trunk Muscle Activity during Drop Jump Performance in Adolescent Athletes with Back Pain

“…Measurement position was defined in a middle position at 17.5° trunk flexion. Further details for the positioning could be seen elsewhere (Mueller et al, 2014). Then, complex motor performance was assessed with drop jumps (DJ).…”

Back Pain in Adolescent Athletes: Results of a Biomechanical Screening

“…A cross-sectional study design was used to evaluate postural control (one-legged stance), jump performance and maximal trunk strength capacity in young athletes with and without back pain. All test situations were implemented as a biomechanical screening tool in the annual (pre-participation) examination of incoming and current students in elite sports schools 23 26 .…”

“…After a 60-s rest period, maximum isokinetic strength was tested concentrically at 60°/s with 5 repetitions and a range of motion (ROM) of 55° (10° extension to 45° flexion; CON-TREX MJ TP 1 000; Physiomed Elektromedizin AG, Germany). Additional information for this standardized trunk testing protocol are detailed in a previous study 26 ( Fig. 1 ).…”

“…For the jumps (CMJ/DJ), jumping height (Height CMJ/DJ ; computed from flight time using the formula: 1/8*g [m/s 2 ] * time [s] 2 ; [cm]), maximum peak force at take-off (Fz CMJ/DJ ; [N]) and ground contact time (Contact DJ ; [ms]) were calculated as the mean of 3 repetitions. Regarding trunk strength testing, absolute peak torque [Nm] in flexion (Flex abs ) and extension (Ext abs ) served as the main outcome measurements and were calculated as the mean of the 3 highest torque values from 5 repetitions 4 26 .…”

“…Furthermore, Zazulak et al showed an association between reduced core stability, reduced muscular trunk strength and a higher injury risk at the lower extremities in young (female) athletes 41 . Differences in trunk strength capacity depending on gender, age and sport type have been identified in healthy adults as well as adolescent athletes 13 26 28 37 . Therefore it might not be valid to transfer results from untrained adults or adult athletes to adolescent athletes.…”