The reliability of linear position transducer and force plate measurement of explosive force-time variables during a loaded jump squat in elite athletes.
The best method of assessing muscular force qualities during isoinertial stretch shorten cycle lower body movements remains a subject of much debate. This study had 2 purposes: Firstly, to calculate the interday reliability of peak force (PF) measurement and a variety of force-time measures, and, secondly, to compare the reliability of the 2 most common technologies for measuring force during loaded jump squats, the linear position transducer (PT), and the force plate (FP). Twenty-five male elite level rugby union players performed 3 rebound jump squats with a 40-kg external load on 2 occasions 1 week apart. Vertical ground reaction forces (GRFs) were directly measured via an FP, and force was differentiated from position data collected using a PT. From these data, a number of force-time variables were calculated for both the FP and PT. Intraclass correlation coefficient (ICC), coefficient of variation (CV), and percent change in the mean were used as measures of between-session reliability. Additionally, Pearson's product moment correlation coefficients were used to investigate intercorrelations between variables and technologies. Both FP and PT were found to be a reliable means of measuring PF (ICC = 0.88-0.96, CV = 2.3-4.8%), and the relationship between the 2 technologies was very high and high for days 1 and 2, respectively (r = 0.67-0.88). Force-time variables calculated from FP data tended to have greater relative and absolute consistency (ICC = 0.70-0.96, CV = 5.1-51.8%) than those calculated from differentiated PT data (ICC = 0.18-0.95, CV = 7.7-93.6%). Intercorrelations between variables ranged from trivial to practically perfect (r = 0.00-1.00). It was concluded that PF can be measured reliably with both FP and PT technologies, and these measurements are related. A number of force-time values can also be reliably calculated via the use of GRF data. Although some of these force-time variables can be reliably calculated using position data, variation of measurement is generally greater when using position data to calculate force.
School of Exercise, Biomedical and Health Sciences, Edith Cowan University, Joondalup, Australia. keir.hansen@warriors.co.uk
Keir T
KT
Hansen
John B
JB
Cronin
Michael J
MJ
Newton
D000293:Adolescent; D000328:Adult; D000886:Anthropometry; D056352:Athletes / Q000706:statistics & numerical data; D001696:Biomechanical Phenomena; D015992:Body Mass Index; D005080:Exercise Test / Q000379:methods; D005538:Football / Q000502:physiology*; D006801:Humans; D008297:Male; D053580:Muscle Strength / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology*; D011187:Posture; D012016:Reference Values; D015203:Reproducibility of Results; D012494:Sampling Studies; D013314:Stress, Mechanical; D013647:Task Performance and Analysis; D014159:Transducers; D016474:Weight-Bearing; D055815:Young Adult