Abstract
ContextStrength-endurance mainly depends on the power output, which is often expressed relative to the individual’s maximal power capability (Pmax). However, an individual can develop the same power, but in different combinations of force and velocity (force-velocity condition). Also, at matched power output, changing the force-velocity condition results in a change of the velocity-specific relative power (Pmaxv), associated with a change in the power reserve. So far, the effect of these changing conditions on strength-endurance remains unclear.PurposeWe aimed to test the effects of force-velocity condition and power output on strength-endurance.MethodsFourteen sportsmen performed (i) force- and power-velocity relationships evaluation in squat jumps and (ii) strength-endurance evaluations during repeated squat jump tests in 10 different force-velocity-power conditions, individualized based on the force- and power-velocity relationships. Each condition was characterized by different (i) relative power (%Pmax), (ii) velocity-specific relative power (%Pmaxv), and (iii) ratio between force and velocity (RFv). Strength-endurance was assessed by the maximum repetitions (SJRep), and the cumulated mechanical work (Wtot) performed until exhaustion during repeated squat jump tests. Intra and inter-day reliability of SJRep were tested in one of the 10 conditions. The effects of %Pmax, %Pmaxv, and RFv on SJRep and Wtot were tested via stepwise multiple linear regressions and two-way ANOVAs.ResultsSJRep exhibited almost perfect intra- and inter-day reliability (ICC=0.94 and 0.92, respectively). SJRep and Wtot were influenced by %Pmaxv and RFv (R2 = 0.975 and 0.971; RSME=0.243 and 0.234, respectively; both p < 0.001), with the effect of RFv increasing with decreasing %Pmaxv (interaction effect, p = 0.03). %Pmax was not considered as a significant predictor of strength-endurance by the multiple regressions analysis. SJRep and Wtot were higher at lower %Pmaxv and in low force-high velocity conditions (i.e., lower RFv).ConclusionStrength-endurance was almost fully dependent on the position of the exercise conditions relative to the individual force-velocity and power-velocity relationships (characterized by %Pmaxv and RFv). Thus, the standardization of the force-velocity condition and the velocity-specific relative power should not be overlooked for strength-endurance testing and training, but also when setting fatiguing protocols.
Highlights
Repetitive near-maximal- or maximal-intensity efforts, such as sprinting, rowing, jumping, or stair climbing, are frequent in daily life and sporting activity
The apex of the P-v relationships corresponds to the maximal power attained at optimal velocity (Pmax), which is commonly accepted as a macroscopic measure of dynamic strength capabilities (Jaric, 2015; Alcazar et al, 2017)
The effect of RFv is further magnified at lower %Pmaxv (Figures 4B,D). These results show that increases in velocity and decreases in force at the same %Pmaxv or %Pmax during acyclic movements are rather beneficial than detrimental and could lead to substantial change in maximum repetitions and cumulated work until exhaustion
Summary
Repetitive near-maximal- or maximal-intensity efforts, such as sprinting, rowing, jumping, or stair climbing, are frequent in daily life and sporting activity. The key to successful performance during repeated movements relies on the production of mechanical power and its maintenance over a series of repetitions until task completion. Power production capabilities depend on movement velocity and are well-represented by the parabolic power-velocity (Pv) relationship during multi-joint movements (Bobbert, 2012; Samozino et al, 2012; Jaric, 2015). The ability to maintain power over a series of movements (i.e., strength-endurance) depends primarily on the output magnitude and is well-illustrated by the power-time relationship. Two distinct power-time relationships have been reported to characterize strength-endurance: (i) the inverse hyperbolic relationship between the absolute or relative power output and the duration during which this given power can be maintained, which can be obtained from 3 to 5 tests to exhaustion (Monod and Scherrer, 1965; Burnley and Jones, 2016), and (ii) the decrease in instantaneous power output over time during a single all-out exercise, which is instead associated with fatigability indices, such as the rate of power output loss over 30-s all-out cycling (Bar-Or, 1987). The same absolute or relative-to-Pmax (%Pmax) power output can be developed in high force-low velocity conditions or in low force-high velocity conditions, and these different force-velocity (F-v) conditions can be interpreted as distinct ratios between the force output and the movement velocity (RFv)
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