Muscle Activity in the Slalom Turn of Alpine Skiing and In-Line Skating

The electromyographic (EMG) activity of seven muscles of the trunk and lower extremity in five male masters level ski racers during a slalom turn in both alpine skiing and in-line skating was recorded using a telemetry system. Measurements were made on separate testing days using slopes commonly used in each activity (24 slope alpine skiing, 5 in-line skating). Qualitative video recorded at 60 Hz was analyzed to partition the turning cycle in both slalom skiing and in-line skating into initiation and turning phases. The EMG data from each turning cycle were normalized to standard isometric contractions (SIC's) for each muscle in order to quantitatively compare the amplitude characteristics of each phase of the turning cycle in both slalom skiing and in-line skating. The turning phase of in-line skating was found to be significantly longer (55%) than in slalom skiing, most likely due to significantly lower subject velocities recorded during in-line skating (8.5 m/s vs 10.2 m/s). All muscles were active at moderate to high levels (48-172% of SIC) during each phase of the turning cycle in both slalom skiing and in-line skating. The EMG amplitude characteristics were similar for six of the muscles in both slalom skiing and in-line skating for each of the turning phases. Only the erector spinae displayed significantly higher average and peak amplitudes in slalom skiing for both phases. It is concluded that the muscle activity patterns associated with the slalom turn of in-line skating are similar but notably more quasi-static than in slalom skiing.