Influence of acute eccentric exercise on the H:Q ratio

Isokinetic Dynamometer Leg Extensor Peak Torque Measurement: A Time-Delayed Reliability and Score Selection Analysis Study

The reliability of isokinetic peak torque (PT) has been reported mostly using a short-term (<~10 day) inter-trial testing time frame. However, many studies and programs utilize a long-term (several weeks to months) inter-trial testing period. Additionally, the methods by which the PT value is selected and reported from a multiple rep testing scheme have not been well investigated for both reliability and PT absolute performance comparisons. The purpose of this study was to investigate the long-term reliability of isokinetic and isometric PT of the leg extensors with an emphasis on the differences among several PT score selection methods. Thirteen men and women (age = 19.5 years) underwent two testing trials separated by 28.8 (±1.8) days. Testing included maximal voluntary contractions of three sets of three reps for two isokinetic contraction conditions of 60 (Isok60) and 240 (Isok240) deg/s velocities, and three sets of one rep of isometric contractions for the leg extensors. The PT score was derived from seven different methods (see text for descriptions). Reliability as assessed from intraclass correlation coefficients (ICCs) varied widely across contraction conditions and PT score selection parameters. The Isok60 velocity overall had lower reliability (ICCs = 0.48-0.81) than Isok240 (0.77-0.87) across the conditions whereas the isometric PT variables showed moderate reliability (0.71-0.73). Overall the set 1 PT score selection parameters were generally lower (p ≤ 0.05) than those that involved sets two and three. Systematic error (p ≤ 0.05) was shown for 6 out of the 17 PT selection variables. On a subjective interpretation basis, when taking everything into account the best overall combination of time/trial efficiency, reliability, best/highest PT score parameter, and reduced risk of systematic bias appears to be the PT variable that uses the average of the highest two reps of the first two sets of three reps-i.e., averaging the highest two values of the six total reps from the first two sets.

Effects of a thorstensson fatiguing protocol on isometric and isokinetic performance

OBJECTIVE: Having participants perform 50 maximal isokinetic contractions, as introduced by Thorstensson and Karlsson (1976), is to this day one of the most commonly used fatigue protocols. Purpose: To determine to what extent a Thorstensson fatiguing protocol affects isokinetic and isometric performance characteristics. METHODS: Twenty-five college-aged men performed an isokinetic fatigue protocol consisting of 50 maximal elbow flexions at a moderate speed (180∘⋅s-1). Pre- and post-tests were used to calculate fatigue indices (FI%) for the following variables: isometric and isokinetic peak torque (PT), isometric rate of torque development (RTD), and maximum acceleration (ACCmax). RESULTS: Each of the four dependent variables significantly decreased with fatigue (each demonstrated p< 0.001), but not of the same magnitude. Isometric PT FI (-18.7%) was significantly less than isokinetic PT FI (-45.1%, p⩽ 0.001) and ACCmax FI (-26.3%) was significantly less than isometric RTD FI (-54.9%, p⩽ 0.001). There was a significant positive relationship between isometric and isokinetic PT FI% (r= 0.60, p< 0.002) as well as between isometric PT FI% and RTD FI% (r= 0.40, p< 0.046). There was no significant relationship observed between RTD FI% and ACCmax FI% nor between isokinetic PT FI% and ACCmax FI%. CONCLUSIONS: This investigation observed different patterns of response in maximal strength between isometric and isokinetic assessments following a isokinetic fatigue protocol. Additionally, the ability to rapidly generate strength and velocity had significantly different responses to fatigue between isometric and dynamic assessments. Due to these different responses, we recommend that assessments of fatigue at least include the same testing modality as the modality of the fatigue protocol.