The effect of different hip rotation angles on electromyography activity of the quadriceps muscle during closed kinetic chain tasks in healthy females.

[Purpose] The purpose of this study was to investigate electromyographic activity of the quadriceps muscle in different positions of hip rotation (while standing on the toes) in healthy females. [Participants and Methods] The study was conducted on 35 healthy females. Electromyographic activity of the rectus femoris, vastus medialis oblique, and vastus lateralis muscles were recorded with the hip in a neutral position as well as different angles of internal and external rotation (15, 30, and 45 degrees (°)) while the participants were standing on their toes. [Results] There was a significant difference of 15° in external rotation, a neutral position, 15° of internal rotation, and at the end of an internal rotation position. Paired comparison between muscle activity using Bonferroni showed that vastus lateralis activity in 15° of external rotation, a neutral position, 15° of internal rotation, and at the end of a position of internal rotation was more than that of rectus femoris muscle. [Conclusion] The present study showed that average vastus lateralis activity was the highest in all positions. However, the positions studied in the current study did not lead to an increase in muscle activity of the vastus medialis oblique as a medial dynamic stabilizer compared to vastus lateralis.

Reliability of dynamic balance simultaneously with cognitive performance in patients with ACL deficiency and after ACL reconstructions and in healthy controls.

PURPOSE: To determine the intra- and inter-session reliability of balance and cognitive performance in anterior cruciate ligament-deficient (ACLD) and ACL-reconstructed (ACLR) and matched athletes. METHODS: Using SMART EquiTest, recovery reactions of the groups were assessed during single-leg standing, following medium and large forward perturbations with and without performing a cognitive (Stroop) task. The outcomes included reaction time (RT), latency and amplitude for balance and error ratio (ER) and RT for cognitive performance. The participants of each group repeated the tests 2-7 days after the first session. Intraclass correlation coefficient (ICC) and standard error of measurement were computed in order to assess relative and absolute reliability, respectively. RESULTS: Single- and dual-task balance measures had moderate to very high reliability in ACLD (ICC = 0.63-0.88), ACLR (ICC = 0.62-0.93) and control (ICC = 0.69-0.98) athletes. The ICCs for RT of Stroop were between 0.87 and 0.90 in ACLD, between 0.70 and 0.74 in ACLR and between 0.66 and 0.70 in controls and for ER of Stroop were between 0.36 and 0.90 in ACLD, between 0.42 and 0.49 in ACLR and between 0.41 and 0.51 in controls. CONCLUSIONS: Balance measures and RT of the cognitive task in single- and dual-task conditions have acceptable reliability and may be incorporated into the evaluation of physical and mental function of athletes following ACL injury and reconstruction. ER of the cognitive task is less reliable which needs to be considered in future research. LEVEL OF EVIDENCE: Prognostic study, case-control, Level III.

The effect of ankle taping and balance exercises on postural stability indices in healthy women.

[Purpose] The purpose of this study was to compare the effect of ankle taping and balance exercises on postural stability indices in healthy women. [Subjects and Methods] Thirty healthy female students were randomly assigned into two equal groups: ankle taping and balance exercise. The balance exercise group performed balance exercises for 6 weeks, with 3 sessions per week and each session lasting 40 minutes. Ankle joint taping was performed for 6 weeks and was renewed three times a week. Before and after the interventions, overall, anteroposterior, and mediolateral stability indices were measured with a Biodex Balance System in bilateral and unilateral stance positions with the eyes open and closed. [Results] In the taping group during bilateral standing with the eyes closed, the overall stability index changed from 6±1.4 to 4.8±1.3, anteroposterior stability index changed from 4.2±1.27 to 3.4±0.97, and mediolateral stability index changed from 3.2±0.75 to 2.7± 0.7. In the balance exercise group during bilateral standing with the eyes closed, the overall stability index changed from 5.7±1.69 to 4.5±1.94, anteroposterior stability index changed from 4.1±1.61 to 3±1.21, and mediolateral stability index changed from 3.5±1.4 to 2.2± 1.3. No significant difference was seen between the two groups regarding any study variables. [Conclusion] The results showed that compared with the taping technique, balance training increases postural stability in the majority of the studied balance situations.

Assessing information of soleous and gastrocnemius motor unit H-reflex response to paired stimulation.

In this study we compared soleous and gastrocnemius muscles responses to paired stimulation in order to reveal the embedded information in H-reflex of these muscles. Four men with ages between 20 and 26 were tested. Since there was no ideal point based on the scientific rules to record H-reflex from gastrocnemius muscle, we were to determine an ideal point and electrode placement from anatomical and physiological point of view. Then, soleous and gastrocnemius muscles were subjected to paired stimulus and H-reflex recovery curve of these muscles were recorded To record the recovery curve, 11 pairs of stimulus were delivered to the posterior tibial nerve. Time interval between the 1st pair of stimulus was 50 ms and increased by 20 ms steps in the next pairs up to 250 ms. The second H-reflex amplitude was divided to the first H-reflex amplitude and expressed in percent, then the recovery curve was drawn accordingly. While the time interval of the paired stimulus was less than 110 ms, the behavior of the curves was similar. In this stage we guessed that the muscles were impressed by the renshaw cells inhibition and the induced fatigue by the first stimulus. When the interval in a pair was 110 ms or more, the recovery percent of soleous was significantly higher than that of the gastrocnemius. This behavior may be due to the less fatigability of soleous motoneurons and less renshaw inhibition on slow motoneurons of soleous. When the time interval of a pair stimulus increases to more than 170 ms, both of the curves behave alike. This may be due to the diminishing of renshaw cell inhibition and the reduction of fatigue. Because of motoneurons physiological properties, when we evoke H-reflex, smaller motoneurons recruit predominantly; but the comparison of the soleous (slow) and gastrocnemius (fast) recovery curves behavior shows that the information about the fast motoneuron are included in H-reflex using this procedure. So we can indirectly assess different motoneurons and renshaw cell activities.