Trunk Muscle Activation During Dynamic Sling Training Exercises.

The purpose of this study was to examine the level of trunk muscle activation to characterize different dynamic sling training exercises. Thirty-six young adults (25±3 years, 1.78±0.1 m, 71.5±10.4 kg) performed six different sling training exercises while muscle activation of eight different trunk muscles was measured unilaterally by surface electrodes. Four of the exercises were conducted at two different difficulty levels (an easy and a hard version) by changing the body angle. The six sling training exercises differed regarding muscle activation, with significant differences (p< 0.05) between the three body parts (front, side, back). High muscle activations (76-87%) of the (front) trunk flexor muscles were measured. The back muscles tested reached more than half of their peak reference trial values only during one exercise tested. Regarding the side muscles, three of the sling exercises achieved muscle activations of 60% and higher (66-92%). All eight trunk muscles tested demonstrated a significantly (p< 0.05) higher muscle activation in the harder version compared with the easy version. Based on the results, the sling training exercises tested in this study seem to be most effective for the abdominal muscles. As assumed based on the former literature, changing the body angle during sling training exercises is shown to be a feasible way of adjusting the intensity of sling training. This could potentially be used in longitudinal sling training studies to assure a controlled, progressively increasing training intervention.