Isokinetic Testing: Sensitivity of the Force-Velocity Relationship Assessed through the Two-Point Method to Discriminate between Muscle Groups and Participants' Physical Activity Levels

Abstract

Background: Isokinetic testing has been routinely used to assess the capacities of individual muscle groups. In this study we aimed to evaluate the sensitivity of the force-point (F-v) relationship assessed through the two-point method to discriminate between antagonist muscle groups and males with different physical activity levels.

Methods: The concentric force output of the knee, hip, elbow, and shoulder flexors and extensors of 27 active and 13 non-active men was recorded at 60 and 180°/s to determine the F-v relationship parameters (maximum force [F₀], maximum velocity [v₀], and maximum power [P_max]).

Results: F₀ and P_max were higher for knee extensors (effect size [ES] = 1.97 and 0.57, respectively), hip extensors (ES = 2.52 and 0.77, respectively), and shoulder flexors (ES = 1.67 and 0.83, respectively) compared to their antagonist muscles, while v₀ was higher for knee flexors compared to knee extensors (ES = 0.59). Active males revealed higher F₀ for knee extensors (ES = 0.72) and knee flexors (ES = 0.83) and higher P_max for knee flexors (ES = 0.70), elbow extensors (ES = 0.83) and shoulder extensors (ES = 0.36).

Conclusions: The sensitivity of the two-point method for testing the maximal mechanical capacities was high for the knee, moderate for the hip and shoulder, and low for the elbow joint.

Keywords: elbow; extensors; flexors; hip; knee; shoulder.

Figure 1

Linear regression models obtained from the force and velocity data averaged across the participants during the knee extension and flexion (upper-left panel), elbow extension and flexion (lower-left panel), hip extension and flexion (upper-right panel) and shoulder extension and flexion (lower-right panel) tasks. Straight and dashed lines represent extensor and flexor muscles, respectively. The error bars represent the standard deviation obtained by flexors (squares) and extensors (circles) groups.

Figure 2

Standardized differences (Effect sizes and 95% confidence intervals) for maximum force (F₀; upper-left panel), maximum velocity (v₀; upper-right panel), force-velocity slope (F-v slope; lower-left panel) and maximum power (P_max; lower-right panel) between the antagonist muscle pairs acting on the knee, hip, elbow and shoulder joints (Effect size = Extensor mean − Flexor mean/SDboth). The probability that the true difference was trivial (ES from −0.20 to 0.20) or substantial is depicted.

Figure 3

Standardized differences (Effect sizes and 95% confidence intervals) for maximum force (F₀; upper-left panel), maximum velocity (v₀; upper-right panel), force-velocity slope (F-v slope; lower-left panel) and maximum power (P_max; lower-right panel) between active and non-active groups for each muscle group. ES, effect size. KE, knee extension; KF, knee flexion; HE, hip extension; HF, hip flexion; EE, elbow extension; EF, elbow flexion; SE, shoulder extension; SF, shoulder flexion. (Effect size = Active mean − Non-active mean/SDboth). The probability that the true difference was trivial (ES from −0.20 to 0.20) or substantial is depicted.