Reproducibility of isokinetic leg strength and endurance characteristics of adult men and women

Abstract

Day-to-day variability and single-measurement reliability of selected isokinetic knee extension-flexion strength and endurance indices were assessed in 10 adult men and 8 adult women. On three occasions separated by at least 5 days, the subjects completed 4 reciprocal maximal voluntary contractions (MVC) at different angular velocities (1.05 rad.s-1 and 3.14 rad.s-1). The men also completed a muscular endurance test consisting of 30 reciprocal, MVC at 3.14 rad.s-1. Coefficient of variation, intra-class correlation coefficient and standard error of single-measurement scores support the continued use of gravity corrected peak torque (PT) and average peak torque (APT) as indices of isokinetic leg strength. Similarly, gravity corrected APT and total work should be the recommended indices of isokinetic leg muscular endurance in men. The results suggest that these isokinetic indices must be assessed using multiple day-to-day trial protocols adequately to describe performance capacity. Composite indices such as the ratio of Knee flexion to extension PT and fatigue measurements offer considerably reduced reliability and a greater potential for misinterpretation. The reliability of knee extension indices generally exceeds that of flexion indices. Similar variability and reproducibility of responses were observed between men and women and between reciprocal contractions performed at angular velocities of 1.05 rad.s-1 and 3.14 rad.s-1.

Knee Joint Strength Ratios and Effects of Hip Position in Rugby Players

“…Repeating this study with a larger sample while concurrently measuring muscle activity using electromyography would be a reasonable approach . 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 In agreement with other studies we have found a significant main effect for velocity on both concentric and eccentric torque production, with greater torque found at the slower velocity (12,15). However, it is important for knee stability that during faster velocity movements that the eccentric hamstring torque is relatively unaffected by velocity to increase the H ecc :Q con to produce less strain on the ACL.…”

“…This can be explained by the main effect of velocity on the absolute values from which the ratios are calculated. However, these results must be read with caution since torque reliability at higher velocities becomes questionable (9,12,28) . 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 As noted previously, isokinetic measurement of knee joint strength balance can be used as a screening tool to predict lower limb musculoskeletal injury (1,8,9,18,22,(24)(25)(26).…”

“…Research in this area has examined strength imbalances on isokinetic devices measuring a range of variables including hamstring and quadriceps torques, conventional hamstring-quadriceps ratio (H con :Q con ), functional hamstring-quadriceps ratio (H ecc :Q con ), bilateral ratios, and stronger-weaker ratios (12,16). The reliability of these measurements at various velocities has been established and some have been shown to be more reliable than others.…”

“…For instance, absolute measures have been shown to be more reliable than strength balance ratios (12,16,28). For absolute measures, the fewer the repetitions the better the reproducibility (12,28); concentric actions have been shown to have greater reliability than eccentric actions (12,28); measurements taken at slower velocities are typically more reliable than measures at high velocity (12,16,17); and less variability has been observed with extensor movements compared to flexor movements (12,28). For strength ratios, H ecc :Q con is reported to be more reliable than others; possibly because H ecc :Q con more accurately reflects the dynamic function of hamstring and quadriceps muscle groups and consequently better describes dynamic muscular stabilization of the knee (16).…”

Effect of Visual Feedback on Muscle Endurance in Normal Subjects

“…Many people have voiced their thoughts on the definition of a fatigue index 17)18) , however, in this research, as was done in the research of Gleeson et al 19) , the fatigue index was calculated by the least squares method. This is because it was thought that while Clarke's SDI formula uses peak torque values at the beginning and end, the fatigue index calculated using the least squares method uses each peak torque value and by this, a more objective endurance index can be acquired.…”