Toe flexor strength in elite female gymnasts compared to toe flexor strength-trained men

Introduction
There is some evidence that intrinsic foot muscles propel the body forward during locomotion [1]. Nearly 80% of intrinsic foot muscles consists of toe flexor muscles (TF) [2] proceeding from the heel to the distal phalanges of the toes. TF’ strength capacity has the potential to enhance jump performance [3]. Since the ability to jump is a performance-limiting factor in gymnastics, we hypothesized that elite female gymnasts’ TF strength is higher than in male sport students, but similar to TF strength-trained men.

Methods
28 female gymnasts (15 ± 2 y, 47 ± 9 kg, 1.56 ± 0.09 m) of the German national team and a basic control group of sport students (n = 28, 25 ± 3 y, 77 ± 8 kg, 1.83 ± 0.06 m) performed three maximum voluntary isometric contractions (MVC) of TF for each foot. TF strength was determined by measuring the moment about the transverse axis of a custom-made dynamometer in 25 degrees toe dorsiflexion. The external moments of force about the axis represented the moments of force produced by the TF [3]. The best of three trials was used for further analysis. Peak moments were determined as the mean value of a 2 s time window of the plateau region. Data were compared to a previous study with the same dynamometer, where a TF strength training group (15 men, 24 ± 4 y, 77 ± 9 kg, 1.85 ± 0.07 m) performed a heavy resistance TF strength training with 90% of MVC for 7 weeks [3]. Statistics: Kolmogorov-Smirnov, unpaired t-test.

Results and Discussion
TF strength significantly differed (p < 0.001) between elite female gymnasts (left: 0.41 ± 0.08 Nm kg^-1, right: 0.45 ± 0.09 Nm kg^-1) and male sport students (left: 0.22 ± 0.05 Nm kg^-1, right: 0.25 ± 0.06 Nm kg^-1). There were no significant differences (p > 0.05) between the TF strength of elite female gymnasts and the male strength training group after 7 weeks of TF strength training (left: 0.38 ± 0.07 Nm kg^-1, p = 0.07, right: 0.40 ± 0.08 Nm kg^-1, p = 0.07).
Adolescent female gymnasts showed 80% to 86% higher TF strength than male sport students, but nearly the same strength level as adult men after 7 weeks heavy resistance TF strength training [3].

Conclusions
TF in elite gymnastics seem to be highly loaded and have to be of particular interest for training and performance enhancement.

References
[1] Farris et al. (2019). PNAS, 116: 1645-1650.
[2] Kura et al. (1997). Anat Rec, 249: 143-151.
[3] Goldmann et al. (2013). J Sport Sci, 31: 424-433.