How the free limbs are used by elite high jumpers in generating vertical velocity

The aim of this study was to quantify how elite high jumpers used their fre e limbs in a competitive high jump and to estimate the contribution that th ese made to vertical take-off velocity. This was achieved by analysing the competitive performances of six elite male high jumpers using 3D motion ana lysis and assessing limb function using the relative momentum method. The m ean peak relative momentum of the arm nearest to the bar at take-off was 9. 4 kg m s(-1), while that of the arm furthest away from the bar was 11.3 kg m s(-1) and these did not differ significantly. The free (lead) leg reached a mean peak relative momentum of 20.9 kg m s(-1). At touch-down the free l eg had a large positive relative momentum that was offset by the negative r elative momentum of the arms, although their combined value still remained positive. The mean combined free limbs' relative momentum at touch-down was 13.8 kg m s(-1) and reached a peak of 37.6 kg m s(-1). The difference betw een these two values amounted to 7.1% of whole-body momentum, which was jud ged to be the amount by which the free limbs contributed to performance. Th e arms had a greater influence on performance than had the lead leg. This w as because the lead leg increased its relative momentum little during the c ontact period while the arms had an initial negative value that increased m arkedly after touch-down. The compressive force exerted by the motion of th e free limbs, estimated by the change in the combined free limbs' relative momentum, reached a mean peak of 366 N and was greatest at 37% of the conta ct period. It was concluded that to maximize the contribution the free limb s can make to performance, given the restraints imposed on technique by oth er performance requirements, the arms should have a vigorous downward motio n at touch-down to make the most use of the high (but little changing) rela tive momentum of the lead leg.