Research in Sport Medicine and Technology

Balance is a complex concept, especially when one wants to do complex motor skills. Therefore, the balance during activity is more important than the static and dynamic balance that is performed without the skill. The aim of this study was to introduce a new activity-based balance index of elite soccer players. 27 young soccer players (12-14 years) whom participated in Iranian premier league were selected. To assess their balance, activity and skill, four functional tests consisting one leg stance, dynamic Y balance, running and dribbling tests were administered. During these tests, besides their relative scores, the acceleration of body center was also recorded using an accelerometer and a new activity-based balance index (ABI) were calculated from these available data. The Results showed a significant positive correlation between ABI and both static and dynamic balance scores(r=0.6, p=0.002). Also, a significant negative correlation was found between ABI and dribbling scores(r=-0.45, p=0.026), which could be interpreted as the necessity of agility of the players. It could be concluded that this new activity-based balance index was found to be successful for evaluating both the balance and the skill level of soccer players.

Although hip muscle strengthening has been reported as an effective way to decrease PFPS symptoms, however its effect on lower extremity kinematics is less clear. The current study was done with the aim of investigating the effect of hip abductor and external rotator muscles strengthening exercises on lower extremity kinematics in static and dynamic states. In a randomized controlled trial, 33 patients with patellofemoral pain (PFP) were randomly assigned into exercise (8 female, 30±6.8 y/o, 23.8±2.6 BMI and 8 male, 31.2±7 y/o, 25.6±1.5 BMI) and control (9 female, 29.9±7.3 y/o, 23.2±3.2 BMI and 8 male, 32±6 y/o, 25.5±1.9 BMI) groups. In exercise group they received hip abductor and external rotator strengthening exercises by thera-band 3 times per week for 12 weeks under supervision by a physiotherapist. The control group did not receive any training intervention. Hip muscles strength and kinematics in static and dynamic states, were assessed at baseline and post-intervention. Repeated measures ANOVA by using SPSS were applied to assess the effects of the exercise on measured variables (α=0/05). After 12 weeks of strengthening program, by an increase in abductor muscle strength in women from 19.6 to 26.4 %BW (P=0.000) and in men from 29.9 to 38.1 %BW (P=0.003), and in hip external rotator muscles in women from 13.2 to 16.9 %BW (P=0.024) and in men from 26.3 to 34.9 %BW (P=0.000), dynamic knee valgus angle during single-legged squat improved in women from 170 to 174.6 degrees (P=0.018) and in men from 171.8 to 176.8 degrees (P=0.017) and contralateral pelvic drop angle during stair descending improved only in women from 7.9 to 6 degrees (P=0.04) in the exercise group. No significant difference was observed at quadriceps angle (P≥0.05). The findings suggest that hip muscles strengthening can alter the lower extremity kinematics, in dynamic state, at the frontal plane, and it might be said that due to these changes following hip abductor and external rotator muscles strengthening exercises by thera-band, the symptoms of PFP improve more consistent.