The aim of this study was to compare the kinetic and kinematic characteristics of plyometric drop-jump and pendulum exercises. Exercises were filmed (100 Hz) from the sagittal view and manually digitized; the data were smoothed and differentiated using cross-validated quintic splines. Ground reaction force data were sampled using a Kistler force platform sampling at 500 Hz. Differences between movement amplitudes and coordination strategies were assessed using t tests and conjugate cross-correlations. Pendulum exercises involved a greater range of motion at the ankle and knee but less motion at the hip joint than drop-jumps. Although different in absolute terms, the exercises used a similar coordination strategy. Drop-jumps resulted in greater peak vertical ground reaction forces than the pendulum exercises although the latter involved a greater net impulse. The similarity between the movement patterns for the two modes of exercise led to the conclusion that pendulum exercises offer a training stimulus similar to that of drop-jumps.
Neil E. Fowler and Adrian Lees
Grace Smith, Mark Lake and Adrian Lees
The metatarsophalangeal joint is an important contributor to lower limb energetics during sprint running. This study compared the kinematics, kinetics and energetics of the metatarsophalangeal joint during sprinting barefoot and wearing standardized sprint spikes. The aim of this investigation was to determine whether standard sprinting footwear alters the natural motion and function of the metatarsophalangeal joint exhibited during barefoot sprint running. Eight trained sprinters performed maximal sprints along a runway, four sprints in each condition. Three-dimensional high-speed (1000 Hz) kinematic and kinetic data were collected at the 20 m point. Joint angle, angular velocity, moment, power and energy were calculated for the metatarsophalangeal joint. Sprint spikes significantly increase sprinting velocity (0.3 m/s average increase), yet limit the range of motion about the metatarsophalangeal joint (17.9% average reduction) and reduce peak dorsiflexion velocity (25.5% average reduction), thus exhibiting a controlling affect over the natural behavior of the foot. However, sprint spikes improve metatarsophalangeal joint kinetics by significantly increasing the peak metatarsophalangeal joint moment (15% average increase) and total energy generated during the important push-off phase (0.5 J to 1.4 J). The results demonstrate substantial changes in metatarsophalangeal function and potential improvements in performance-related parameters due to footwear.
Adrian Lees, Philip Graham-Smith and Neil Fowler
This study was concerned with the measurement of performance variables from competitors in the men's long jump final of the World Student Games held in Sheffield, England, in July 1991. Several performances of 10 finalists were recorded on cine film at 100 Hz. Resulting sagittal plane kinematic data were obtained for the last stride, touchdown, and takeoff for a total of 27 jumps. It was confirmed that takeoff velocity was a function of touchdown velocity, and that there was an increase in vertical velocity at the expense of a reduction of horizontal velocity. It was concluded that there was evidence for mechanisms which may be termed mechanical, biomechanical, and muscular. The former relates to the generation of vertical velocity by the body pivoting over the base of support during the compression phase, and a lifting of the arms and free leg during the lift phase; the second is the elastic reutilization of energy; and the third is the contribution by concentric muscular contraction.
John Iga, Keith George, Adrian Lees and Thomas Reilly
Using 95% limits of agreement (LOA), this study examined the reproducibility of indices of isokinetic leg strength in pubertal soccer players. Following familiarization, 23 boys performed isokinetic assessments of the knee joint muscles at 1.08, 2.16, and 4.32 rad/s during concentric exercise and at 2.16 rad/s during eccentric actions on two separate occasions. Peak torque values were recorded and reciprocal and bilateral muscle group ratios were calculated. As random error was heteroscedastic, 95% ratio LOA were employed. Systematic bias for the various measurements ranged from 0.97 to 1.07 for all data. Random variation associated with eccentric assessments of the hamstrings, concentric H:Q ratio calculated at 1.08 rad/s, and HECC:QCON ratios appeared narrow enough to be of practical use (×/÷ 1.05 to 1.20). Random errors associated with H:Q ratios calculated at high concentric velocities (4.32 rad/s) and during eccentric exercise (×/÷ 1.10 to1.37), and in all bilateral muscle group ratios (×/÷ 1.15 to 1.43) were too broad, rendering them prone to misinterpretation.