There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.
Abstract
Proximal-distal differences in muscle activity are rarely considered when defining
the activity level of hamstring muscles. The aim of this study was to determine the
inter-muscular and proximal-distal electromyography (EMG) activity patterns of hamstring
muscles during common hamstring exercises. Nineteen amateur athletes without a history
of hamstring injury performed 9 exercises, while EMG activity was recorded along the
biceps femoris long head (BFlh) and semitendinosus (ST) muscles using 15-channel high-density
electromyography (HD-EMG) electrodes. EMG activity levels normalized to those of a
maximal voluntary isometric contraction (%MVIC) were determined for the eccentric
and concentric phase of each exercise and compared between different muscles and regions
(proximal, middle, distal) within each muscle. Straight-knee bridge, upright hip extension,
and leg curls exhibited the highest hamstrings activity in both the eccentric (40%-54%MVIC)
and concentric phases (69%-85%MVIC). Hip extension was the only BF-dominant exercise
(Cohen's d = 0.28 (eccentric) and 0.33 (concentric)). Within ST, lower distal than
middle/proximal activity was found in the bent-knee bridge and leg curl exercises
(d range = 0.53-1.20), which was not evident in other exercises. BFlh also displayed
large regional differences across exercises (d range = 0.00-1.28). This study demonstrates
that inter-muscular and proximal-distal activity patterns are exercise-dependent,
and in some exercises are affected by the contraction mode. Knowledge of activity
levels and relative activity of hamstring muscles in different exercises may assist
exercise selection in hamstring injury management.