Shuhei Numano

CHARACTERISTICS OF ANKLE MUSCLE ACTIVITY DURING TILTING MOVEMENTS ON A WOBBLE BOARD

Background Balance training is a common component of rehabilitation after ankle sprains. A relatively high activity of the peroneus longus (PL) to the activity of the tibialis anterior (TA) (a low TA/PL ratio) is reported as an effective muscle activity pattern during balance training to prevent inversion ankle sprains. To date, no research has investigated ankle muscle activity during tilting movements on a wobble board. Objective To assess the magnitude of muscle activity of the ankle while inversion and eversion movements of the ankle joint are performed on a wobble board. Design Single-session randomized repeated-measures study design. Setting University laboratory. Participants Seventeen young adults (11 females and 6 males) with no history of ankle injury. Interventions Participants performed tilting movements on a wobble board in a medial and lateral direction while balancing on their non-dominant leg. The frequency of the movement was set at 40 bpm. Muscle activity of the TA and the PL during five cycles of inversion-eversion movements were collected and stored for analysis. Main Outcome Measurements Normalized RMS EMG values (percentage of each participants maximum voluntary isometric contraction; %MVIC) of the TA and PL, along with TA/PL ration in the inversion (wobble board tilted in the lateral direction) and eversion (wobble board tilted in the medial direction) phase. Results There was a significant difference in muscle activity of the PL (inversion phase; 41.6±15.3%MVIC, eversion phase; 59.2±21.5% MVIC, p<0.01) and TA/PL ratio (inversion phase; 52.6±22.3%, eversion phase; 34.1±16.3%, p<0.01). There was no significant difference in muscle activity of the TA (p>0.05). Conclusions The results of the present study indicate that tilting movements on a wobble board in the medial direction (eversion of the ankle joint) may be favorable as an exercise modality after inversion ankle sprains as a high PL activity and a low TA/PL ratio was acquired.