Supervisors info:
Ρουσάνογλου Ε., Καθηγήτρια, ΣΕΦΑΑ, ΕΚΠΑ
Μπουντόλος Κ., Καθηγητής, ΣΕΦΑΑ, ΕΚΠΑ
Τσιόκανος Α., Καθηγητής, ΣΕΦΑΑ, Πανεπιστήμιο Θεσσαλίας
Summary:
Leg stiffness (LS) is a variable of performance and motor control that reflects the spring function of the lower extremities (storage and release of elastic energy). The LS seems to increase inversely proportional to the stiffness of the contact surface. It also varies as an adaptation of the sport specialization. The sport shoe is an interface between the foot and the contact surface and a potential co-moderator of the LS. For its evaluation, the two-legged hopping in place constitutes an ideal motor pattern, with the stiffness of the ankle having a dominant role, due to the intense (pre)activation of the external gastrocnemius muscle.
The purpose of the present study was: (A) to examine the effect of sport footwear on LS and the gastrocnemius muscle activation and (B) to test the significance of the interaction between sport footwear and sport specialization.
Elite level basketball (BG: N = 14) and volleyball (VG: N = 14) women athletes participated in the study. Also, 14 women matched to the athletes’ age and anthropometric characteristics served as the control group (CG). The participants performed two-legged hopping in place landing on a forceplate (Kistler 9286AA, Switzerland) for the recording of the vertical (V) ground reaction force (GRF) pattern. In synchronization, with the VGRF, the activation of the external gastrocnemius muscle was recorded (vibromyograph, VMG Transducer, TSD250, Biopac Systems) and optical motion recording was also applied (sagittal plane Biopac Systems). They all performed the two-legged hopping in place in two conditions: barefoot (B) and with shoes (S), at 2.2 Hz following a metronome set at 130bpm. The LS, the spatial and temporal variables of the VRF profile and the muscle activation of the external gastrocnemius muscle (VMG units) were used for statistical analysis. A mixed two-way analysis of variance (3 X 2) was applied to test the interaction between sport specialization and footwear, as well as the footwear main effect (SPSS v. 28.0, p ≤ 0.05).
Without a significant interaction between sport specialization and footwear (p > 0.05) and regardless of the calculation method, the LS difference between the B and the S condition was not significant (p > 0.05). As a main effect (Ν = 42), footwear significantly changed (p ≤ 0.05) the hopping kinetic pattern (higher VGRF, p = 0.033), the timing pattern of the hopping cycle (higher absolute p = 0.022 and relative p = 0.005 contact time, shorter absolute p = 0.004 and relative p = 0.005 flight time) as well as the hopping spatial pattern (lower jump height, p = 0.035). Muscle activation revealed a significant interaction between sport specialization and footwear concerning the flight to contact percentage ratio (p = 0.007). Pairwise comparisons revealed greater muscle activation in the VG compared to the other two groups, but not in both footwear conditions (B for CG, p= 0.042 and S for BG, p = 0.023). Concerning the footwear main effect for the total group of participants (N = 42), in the S condition the gastrocnemius muscle activation was lower during the contact phase (p = 0.017).
In conclusion, during two-legged hopping in place at 2.2 Hz, footwear seems to allow a better mechanical economy of the lower extremity (most possibly due to lower muscle activation in the contact phase) and a rather lower mechanical loading (longer contact duration) Sport specialization does not appear to alter the footwear effect.
