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Effects of Crouch Position on Performance for Skiers

The last 10 years has brought some changes in the sports world. Sprinting has become a new event in ski-skating. Ski-skating is the freestyle cross-country skiing event. In this study, researchers at the Human Movement Science Programme in Norway look at the effect of body position on performance for this event.

Three different body positions (high, moderate, and deep) were compared. High is an upright position. Deep is more of a crouch position, and moderate is somewhere in between. The theory is that at high speeds, a crouch position would decrease air resistance. The result could be to decrease the skier's time for the event.

One possible disadvantage of the deeper position is the need for greater muscle control and the effort required to stay in that position. Blood flow may be slowed down because of the flexed position of the legs. Fatigue may be a factor. And the skier can't use his or her arms in this position.

Does the increased power from a deep position make up for the fatigue and loss of arm power?

Human movement engineers were able to study this question using a slide board with force plates in a wind tunnel. Male and female cross-country skiers were included in the study. Skiers participated in both a 30-second and a three-minute test.

Videos were used to record push-off and gliding movements. Power loss and friction forces were calculated. Oxygen use, heart rate, and lactate levels in the blood were measured for each skier. Lactate (also known as lactic acid) builds up in the blood when muscles are used without oxygen. A higher lactate level is more likely when the skier is crouched down because blood supply to the legs is less in this position.

The results showed a 30 per cent decrease in air resistance from the high to low position. This change means there's a power loss in the low position. Power loss was greater in the three-minute test. This was probably caused by fatigue during the longer test.

Heart rate was the same in all three positions. Skiers used more oxygen in the high position. As expected, greater lactate levels were measured in the deep position.

The authors conclude that the deep crouch position may improve performance during sprinting.

Training will be needed to maintain this position for longer distances but the benefits may make it worthwhile. Even without the force generated by using the arms, a deep body position over longer distanced in ski-skating may give the skier a greater overall advantage.

References: Stig Leirdal, et al. Effects of Body Position on Slide Boarding Performance by Cross-Country Skiers. In Medicine & Science in Sports & Exercise. August 2006. Vol. 38. No. 8. Pp. 1462-1469.

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