Individual Force-velocity Relationships Research Articles

Comparison of different regression models to fit the force–velocity relationship of a knee extension exercise

The aims of this study were to compare the goodness of fit and the concurrent validity of three regression models of the force–velocity relationship in a unilateral knee extension exercise. The force–velocity relationship and the one-repetition-maximum load in the dominant and non-dominant leg were obtained in 24 male sports sciences students by a progressive protocol. Additionally, the maximum voluntary contraction (MVC) of the knee extensor muscles was recorded. Individual force–velocity relationships were obtained by the linear, quadratic polynomial and exponential regression models. Although the adjusted coefficients of determination of all three models were high, the polynomial model’s coefficient was slightly but significantly higher than the rest of the models (p < 0.05), while the standard error of estimate was slightly higher for the linear than for polynomial model (p = 0.001). MVC was underestimated by F 0 calculated from the linear and polynomial models, while the maximum power was accurately estimated by the linear model. In summary, while the polynomial model revealed somewhat better fit, the linear model more accurately estimates the maximum power and provides the parameters of apparent physiological meaning. Therefore, we recommend using the linear model in research and routine testing of mechanical capacities of knee extensors.

Optimal Balance Between Force and Velocity Differs Among World-Class Athletes.

Performance during human movements is highly related to force and velocity muscle capacities. Those capacities are highly developed in elite athletes practicing power-oriented sports. However, it is still unclear whether the balance between their force and velocity-generating capacities constitutes an optimal profile. In this study, we aimed to determine the effect of elite sport background on the force-velocity relationship in the squat jump, and evaluate the level of optimization of these profiles. Ninety-five elite athletes in cycling, fencing, taekwondo, and athletic sprinting, and 15 control participants performed squat jumps in 7 loading conditions (range: 0%-60% of the maximal load they were able to lift). Theoretical maximal power (Pm), force (F0), and velocity (v0) were determined from the individual force-velocity relationships. Optimal profiles were assessed by calculating the optimal force (F0th) and velocity (v0th). Athletic sprinters and cyclists produced greater force than the other groups (P < .05). F0 was significantly lower than F0th, and v0 was significantly higher than v0th for female fencers and control participants, and for male athletics sprinters, fencers, and taekwondo practitioners (P < .05). Our study shows that the chronic practice of an activity leads to differently balanced force-velocity profiles. Moreover, the differences between measured and optimal force-velocity profiles raise potential sources of performance improvement in elite athletes.

Force–velocity characteristics of upper limb extension during maximal wheelchair sprinting performed by healthy able-bodied females

The aim of this study was to determine the relationship between force and velocity parameters during a specific multi-articular upper limb movement – namely, hand rim propulsion on a wheelchair ergometer. Seventeen healthy able-bodied females performed nine maximal sprints of 8 s duration with friction torques varying from 0 to 4 N · m. The wheelchair ergometer system allows measurement of forces exerted on the wheels and linear velocity of the wheel at 100 Hz. These data were averaged for the duration of each arm cycle. Peak force and the corresponding maximal velocity were determined during three consecutive arm cycles for each sprint condition. Individual force–velocity relationships were established for peak force and velocity using data for the nine sprints. In line with the results of previous studies on leg cycling or arm cranking, the force–velocity relationship was linear in all participants (r = −0.798 to −0.983, P <0.01). The maximal power output (mean 1.28 W · kg−1) and the corresponding optimal velocity (1.49 m · s−1) and optimal force (52.3 N) calculated from the individual force–velocity regression were comparable with values reported in the literature during 20 or 30 s wheelchair sprints, but lower than those obtained during maximal arm cranking. A positive linear relationship (r = 0.678, P <0.01) was found between maximal power and optimal velocity. Our findings suggest that although absolute values of force, velocity and power depend on the type of movement, the force–velocity relationship obtained in multi-articular limb action is similar to that obtained in wheelchair locomotion, cycling and arm cranking.