Force stability training decreased force variability of plantar flexor muscles without reducing postural sway in female older adults.

BACKGROUND: Previous studies reported a relationship between postural sway and force variability of the plantar flexor muscles (PFM), such that less force variability related to lower postural sway; however, this association does not seem to exist in older adults. RESEARCH QUESTION: This study investigated the effect of force stability training of the PFM on force variability (FV) of these muscles and postural sway in female older adults. METHODS: Thirty female older adults were divided into three groups: TG5 (n = 10), who trained at 5% of maximum voluntary isometric contraction (MVIC) of the PFM; TG10 (n = 10), who trained at 10 % of MVIC of the PFM; and CG (n = 10) who did not perform any specific training for the PFM. Postural sway was evaluated during upright bipodal posture. Postural sway and FV of the PFM were assessed before and after the training period. Participants trained once a week for four weeks. RESULTS: After the training period, the FV decreased significantly for both TG5 (pre = 3.26 ± 0.83; post = 2.53 ± 0.60 N) and TG10 (pre = 3.50 ± 0.72; post = 2.85 ± 0.86 N), but the mean sway amplitude increased for both TG5 (pre = 0.017 ± 0.03; post = 0.19 ± 0.04 cm) and TG10 (pre = 0.14 ± 0.04; post = 0.16 ± 0.04 cm). SIGNIFICANCE: The force stability training decreased the FV of the PFM, but this decrease was insufficient to reduce postural sway in female older adults.

The variability of the force produced by the plantar flexor muscles does not associate with postural sway in older adults during upright standing.

The force variability of the plantar flexor muscles (PFM) appears to be directly related to the control of upright standing. Nevertheless, this association is still uncertain in older adults. This study aimed to evaluate the relationship between PFM force variability and postural sway in the upright standing in older women. Forty older women performed submaximal plantar flexion movements measured by force transducers coupled to an experimental chair. They performed this task during three sets of 20 s at 5% and 10% of their maximum voluntary isometric contraction with and without the aid of visual feedback of the force produced. The volunteers then stood barefoot, with eyes closed and feet parallel on a force platform, which allowed the measurement of the center of pressure displacement in the anteroposterior direction. The results did not indicate a significant association between force variability of the PFMs and postural sway in older women. It can be inferred that the force variability of the PFM does not play an important role in controlling the posture in this population, suggesting that other factors may influence the functioning of the postural control system in older adults.

Training Level Does Not Affect Auditory Perception of The Magnitude of Ball Spin in Table Tennis.

Identifying the trajectory and spin of the ball with speed and accuracy is critical for good performance in table tennis. The aim of this study was to analyze the ability of table tennis players presenting different levels of training/experience to identify the magnitude of the ball spin from the sound produced when the racket hit the ball. Four types of "forehand" contact sounds were collected in the laboratory, defined as: Fast Spin (spinning ball forward at 140 r/s); Medium Spin (105 r/s); Slow Spin (84 r/s); and Flat Hit (less than 60 r/s). Thirty-four table tennis players of both sexes (24 men and 10 women) aged 18-40 years listened to the sounds and tried to identify the magnitude of the ball spin. The results revealed that in 50.9% of the cases the table tennis players were able to identify the ball spin and the observed number of correct answers (10.2) was significantly higher (χ2 = 270.4, p <0.05) than the number of correct answers that could occur by chance. On the other hand, the results did not show any relationship between the level of training/experience and auditory perception of the ball spin. This indicates that auditory information contributes to identification of the magnitude of the ball spin, however, it also reveals that, in table tennis, the level of training does not interfere with the auditory perception of the ball spin.