Comparison between gymnasts and non-gymnasts in isometric strength of the lower limbs

Injury, Training, Biomechanical, and Physiological Profiles of Professional Breakdancers

Background

Breakdancing or breaking will enter the Olympics in 2024, however, there is a paucity of literature exploring the epidemiology, demands, and performance.

Purpose

The purpose of this study was to describe injury and training profiles, along with the results of a short performance test battery, in a group of elite breakers.

Study Design

Cross-sectional study (retrospective).

Methods

Fourteen breakdancers (breakers) (4 Bgirls, 10 Bboys) participated in an interview regarding their injury and training history, endurance test (cycle VO2max testing), counter movement jump, squat jump, drop jump, isometric hip abduction, adduction, shoulder external and internal rotation strength testing on a fixed-frame dynamometer. Breakers were divided into elite (n=10) and developing (n=4) based on their qualification for a world finals competition; Wilcoxen rank sums were used to compare the two groups, or in the case of strength testing between those with and without an injury history.

Results

The breakers had a median 11.0 [10.0 - 14.0] years breaking experience and trained 24.4 [20.5 - 30.0] hours per week. The knee was the most commonly injured body part and most frequently injured joint, with the thigh being the most common site for muscle injuries. There were no differences in endurance testing or jump height testing results between elite and developing breakers. There was no difference in shoulder external or internal rotation strength between athletes with a history of shoulder injury and those without. Similarly, there was no difference in hip abduction or adduction strength in those with a history of hip injury and those without.

Conclusion

The results of this study should be viewed with caution due to the small sample size. However, this study is the first to publish functional and physiological descriptives on breakers. The authors hope these results support clinicians treating breakers as well as encourages future research related to breaking.

Level of Evidence

2b.

Postural Control in Unipedal Quiet Stance in Young Female Gymnasts and the Effects of Training with Consideration of Transient Behavior of Postural Sway

The purpose of this study was twofold: (a) to compare postural control between a group of young female gymnasts (n = 15; age: 11.2 ± 1.9 years) and non-trained peers (n = 15; age: 10.9 ± 2.0 years), and (b) to investigate the effect of an 8-week whole body exercise intervention program on postural control in young female gymnasts. Postural control was assessed by recording center of pressure (CoP) movements during unipedal quiet stance. Velocity and amplitude of CoP movement in anterior-posterior (AP) and medial-lateral (ML) directions were considered. In addition to common trial-averaged CoP outcomes, we also considered the transient behavior of CoP movements, by calculating relative differences between the 1st and 2nd, and the 1st and 3rd 10-s intervals within the whole trial (DIF_21 and DIF_31, respectively). The gymnast group had lower total CoP velocity (Cohen's d = 0.97) and AP amplitude (Cohen's d = 0.85), compared to their non-trained peers. The gymnasts also had lower CoP AP amplitude DIF21 (Cohen's d = 0.73), with almost constant values across all intervals. After the training ML CoP velocity was reduced for 13.12% (Cohen's d = 0.60), while ML CoP amplitude increased (Cohen's d = -0.89).

Assessment of the Adaptive Force of Elbow Extensors in Healthy Subjects Quantified by a Novel Pneumatically Driven Measurement System with Considerations of Its Quality Criteria

Adaptive Force (AF) reflects the capability of the neuromuscular system to adapt adequately to external forces with the intention of maintaining a position or motion. One specific approach to assessing AF is to measure force and limb position during a pneumatically applied increasing external force. Through this method, the highest (AF_max), the maximal isometric (AFiso_max) and the maximal eccentric Adaptive Force (AFecc_max) can be determined. The main question of the study was whether the AFiso_max is a specific and independent parameter of muscle function compared to other maximal forces. In 13 healthy subjects (9 male and 4 female), the maximal voluntary isometric contraction (pre- and post-MVIC), the three AF parameters and the MVIC with a prior concentric contraction (MVICpri-con) of the elbow extensors were measured 4 times on two days. Arithmetic mean (M) and maximal (Max) torques of all force types were analyzed. Regarding the reliability of the AF parameters between days, the mean changes were 0.31–1.98 Nm (0.61%–5.47%, p = 0.175–0.552), the standard errors of measurements (SEM) were 1.29–5.68 Nm (2.53%–15.70%) and the ICCs(3,1) = 0.896–0.996. M and Max of AFiso_max, AF_max and pre-MVIC correlated highly (r = 0.85–0.98). The M and Max of AFiso_max were significantly lower (6.12–14.93 Nm; p ≤ 0.001–0.009) and more variable between trials (coefficient of variation (CVs) ≥ 21.95%) compared to those of pre-MVIC and AF_max (CVs ≤ 5.4%). The results suggest the novel measuring procedure is suitable to reliably quantify the AF, whereby the presented measurement errors should be taken into consideration. The AFiso_max seems to reflect its own strength capacity and should be detected separately. It is suggested its normalization to the MVIC or AF_max could serve as an indicator of a neuromuscular function.