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

Abstract 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.