The mechanics of moving along a curved path suggest that runners must change their body positions and thus adjust their lower extremity function as they accomplish a track turn. The purpose of the present study was to investigate the changes in the kinetics and kinematics of the lower extremity as runners proceed around the turn of a 400-m track (radius 31.5 m). Five skilled runners served as subjects in the study and were required to perform 10 trials in three conditions, running at 6.31 m/s plus or minus 5% (4:15 min/mile pace). The right and left limbs on a track turn and the right limb on the straightaway were evaluated using ground reaction force data and kinematic data from high-speed film. Statistical analysis of the 18 ground reaction force variables and 4 kinematic variables suggested that the right and left limbs at the midpoint of the track turn were asymmetrical and that most of the differences occurred in the first portion of the footfall Significant differences were found in the touchdown angle, maximum pronation angle, all mediolateral variables, and in the vertical variables describing the collision phase of the footfall (p < .05). The data suggest that the etiologies of injuries to the right and left lower extremity differ, with right foot injuries being of the impact type and left leg injuries being of the overpronation type.
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The Effects of Track Turns on Lower Extremity Function
Joseph Hamill, Michael Murphy, and Donald Sussman
Relationship between Maximum Strength and Relative Endurance for the Empty-Can Exercise
Martha Walker, Donald Sussman, Michael Tamburello, Bonnie VanLunen, Elizabeth Dowling, and Beth Ernst Jamali
Context:
A strength-endurance diagram predicts that a person should be able to perform 30 repetitions of an exercise if the resistance level is 60% of 1-repetition maximum (1RM).
Objective:
To compare the number of repetitions predicted by the diagram with recorded repetitions of a shoulder exercise.
Design:
Single-group comparison with a standard.
Setting:
University.
Participants:
34 healthy adults (20 women, 14 men) with a mean age of 29 years (range 20–49).
Main Outcome Measures:
The number of repetitions that subjects could perform in good form of a shoulder exercise with resistance of 60% 1RM.
Results:
The mean number of repetitions was 21 (± 3, range 15–28), which was significantly different than the 30 repetitions that the diagram predicted.
Conclusions:
The strength-endurance diagram did not accurately predict the number of repetitions of a shoulder exercise that subjects could perform.