Comparison of lower limb muscle activities during eccentric lunge walking in three different step lengths

PURPOSE: Eccentric lunge walking (ELW), which requires body weight to be supported by the stepping leg for ~ 3 s while its knee is flexed to ~ 90º (eccentric phase), has been shown to improve physical function. However, the influence of step length on lower-limb muscle activities during ELW remains unclear. We hypothesised that a longer-than-normal step length would increase knee and hip extensor muscle activities during the eccentric phase of ELW. METHODS: Surface electromyogram (EMG) was recorded from vastus lateralis (VL), vastus medialis, rectus femoris, biceps femoris, gluteus maximus (GM), and gastrocnemius of 15 healthy adults (30-64 y). Participants performed ELW under three step length conditions: normal, 20% (+ 20%), and 40% longer than normal (+ 40%). Absolute root mean square (RMS) and normalized it to maximal voluntary isometric contraction (%MVIC) EMG amplitudes in eccentric, isometric, and concentric phases were compared between the conditions using one-way repeated-measures ANOVA. RESULTS: Peak knee flexion angle increased (p < 0.01) progressively from normal (70.3 ± 13.9°) to + 20% (81.1 ± 14.2°) and + 40% step length (85.6 ± 16.7°). However, step length had no significant effect (p > 0.05) on absolute or %MVIC muscle activity during the eccentric or isometric phases. During the concentric phase, VL and GM activities were greater (p < 0.05) in the + 40% (105.6 ± 79.2% and 78.1 ± 61.0%MVIC respectively) than in the normal condition (87.6 ± 67.3% and 53.4 ± 41.0%MVIC respectively). CONCLUSION: Contrary to hypothesis, longer step lengths did not increase eccentric phase knee and hip extensor activities, but made the returning concentric phase movements more difficult. Thus, a normal step length appears sufficient for ELW.