ABDOMINAL AND HIP FLEXOR MUSCLE ACTIVATION DURING VARIOUS TRAINING EXERCISES

The purpose of this study was to provide objective information on the involvement of different abdominal and hip flexor muscles during vario us types of common training exercises used in rehabilitation and sport . Six healthy male subjects performed altogether 38 different static a nd dynamic training exercises - trunk and hip flexion sit-ups, with va rious combinations of leg position and support, and bi- and unilateral leg lifts. Myoelectric activity was recorded with surface electrodes from the rectus abdominis, obliquus externus, obliquus internus, rectu s femoris, and sartorius muscles and with indwelling fine-wire electro des from the iliacus muscle. The mean electromyogram amplitude, normal ised to the highest observed value, was compared between static and dy namic exercises separately. The hip flexors were highly activated only in exercises involving hip flexion, either lifting the whole upper bo dy or the legs. In contrast, the abdominal muscles showed marked activ ation both during trunk and hip flexion sit-ups. In hip flexion sit-up s, flexed and supported legs increased hip flexor activation, whereas such modifications did not generally alter the activation level of the abdominals. Bilateral, but not unilateral, leg lifts required activat ion of abdominal muscles. In trunk flexion sit-ups an increased activa tion of the abdominal muscles was observed with increased flexion angl e, whereas the opposite was true for hip flexion sit-ups. Bilateral le g lifts resulted in higher activity levels than hip flexion sit-ups fo r the iliacus and sartorius muscles, while the opposite was true for r ectus femoris muscles. These data could serve as a basis for improving the design and specificity of test and training exercises.