Reliability and validity of a new device to measure isometric strength in polyarticular exercises.
BACKGROUND
The purpose of this study was to assess the validity of a new device to evaluate isometric strength during multi-joint exercise such as the squat or bench press.


METHODS
The device used an electric motor-driven bar to simultaneously generate and measure forces during weight lifting exercises. This new device and a force platform measured the forces generated by either the motor on a fixed telescopic steel girder (passive condition) or a subject pushing vertically against the bar from three squat positions (active condition). In the passive condition, 252 measurements were made, with 3 trials for 6 bar heights and 14 bar loads. In the active condition, 8 young physically active students (age, height and body mass were 25.1 +/- 2.6 years, 179.3 +/- 7.2 cm and 82.0 +/- 9.9 kg, respectively) performed 3 maximal isometric strength (MIS) trials in each of the 3 squat exercise positions (parallel, half and quarter squat), and 3 additional MIS trials in one position randomly assigned two weeks later to test inter-day reliability.


RESULTS
In the passive condition, no differences were observed between the forces measured by the force platform and the new device. The coefficient of linear regression (r) and the coefficient of variation (CV) were 1 and below 0.23%, respectively. In the active condition, the peak MIS measured was 2828 N and the values of r and CV were above 0.982 and below 5.96%, respectively. The assessment of inter-day reliability showed an r value of 0.984 and a CV of 3.98%.


CONCLUSIONS
This study demonstrated that the new electric motor-driven exerciser provides valid and reliable data when used to generate forces and measure isometric strength throughout the load and motion ranges commonly used in squat exercise.
Laboratoire de Recherche sur les Activités Physiques et Sportives UFR STAPS, Université de Nice Sophia-Antipolis, France.
F
F
Verdera
L
L
Champavier
C
C
Schmidt
S
S
Bermon
P
P
Marconnet
D000328:Adult; D000704:Analysis of Variance; D001696:Biomechanical Phenomena; D004867:Equipment Design; D005080:Exercise Test / Q000295:instrumentation*; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D016014:Linear Models; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D015203:Reproducibility of Results; D013314:Stress, Mechanical; D014891:Weight Lifting / Q000502:physiology*