Differences in Utilization of Lower Limb Muscle Power in Squat Jump With Positive and Negative Load

Abstract

Jump performance is related to the ability of lower limb muscles to produce power during the push-off phase. However, it is not known if the power associated with the action of active and passive elements of the lower limb muscles change significantly in jumps with positive and negative loads. In this study, the power associated with the action of passive and active components of lower limb muscles as a whole in squat jumps (SJ) with increase and decrease in the external load is analyzed Fourteen trained male subjects (22.5 ± 2.1 years; 176.5 ± 5.4 cm; 75.8 ± 5.8 kg; BMI 24.3 ± 1.8) performed SJ on a force plate. A functional electromechanical dynamometer (FEMD) system was used to change the external load in a range of −30 to +30% of the subject’s body weight. A model comprising a mass, a spring, an active element, and a damper was used. We applied an optimization principle to determine power in center of mass (CoM) (ptot), the powers associated with active element (pact), damper (pƔ), and spring (pk) during the push-off phase. Significant differences between loading conditions for each variable were tested by repeated-measures one-way ANOVA with Bonferroni post hoc analysis, p < 0.05. Shapes of the average curves for instantaneous variation of pact, pƔ, pk, and ptot during push-off with positive loads were closer to 0% than with negative loads. As the load increased, maximum values of ptot, pƔ, and pk decreased. Only with a negative load of −30% did ptot increase significantly, this was not accompanied by changes in pact, pƔ, and pk. The load of one’s own body provides conditions for develop high pact peaks, although the maximum ptot is not achieved in that condition. The increase in negative loads produces a significant increase in ptot, but not in pact and can be interpreted as a situation in which the power delivered to the system by the action of active components is better used. The SJ with positive load, although more similar to the instantaneous changes that occur to the SJ with body weight are not gestures where high power is developed.

Exploration of the Shoulder Internal Rotation’s Influence on Throwing Velocity in Handball Players: A Pilot Study

“…FEMD requires the active stabilization of participants in strength assessments, which enables a better posture for the strength application in handball-throwing sports. Previous research used FEMD in a novel way to evaluate the trunk [ 31 , 32 ], lower limb [ 33 , 34 , 35 ] isometric hip strength [ 36 ], muscle quality and isometric strength in elderly women [ 37 ] and in older adults with hip osteoarthritis [ 37 , 38 ], and shoulder rotator strength [ 25 , 39 ]. However, FEMD has never been used to calculate the F-V profile, and shoulder internal rotation strength has never been assessed in an isotonic way.…”

Test–Retest Reliability of Functional Electromechanical Dynamometer on Five Sit-to-Stand Measures in Healthy Young Adults

“…Currently, the development of the functional electromechanical dynamometer (FEMD) (as opposed to the angular isokinetic devices) [ 28 ] allows systematizing and controlling multiple components of the load during the performance of natural movements, such as the range and velocity of movement, magnitude of resistance, control of strength exercised and type of muscle contraction (isometric, concentric and eccentric). In this regard, studies have assessed the reliability and validity [ 29 , 30 , 31 , 32 ] and used the FEMD [ 33 , 34 , 35 , 36 , 37 , 38 ] under different experimental modalities and muscle groups. However, studies that propose to assess the reliability of the STS test using this type of technology have not been previously developed.…”

Test-retest reliability of a functional electromechanical dynamometer on swing eccentric hamstring exercise measures in soccer players

“…This exercise, we propose, simulates the late swing phase of high speed running by combining hip flexion with knee extension, a mechanism performed during the sprint (Chumanov, Heiderscheit & Thelen, 2011;Chumanov et al, 2012). Similarly, it is also important to use measuring devices that allow movements similar to sports specific movement to be replicated, such as a functional electromechanical dynamometer (FEMD), which allows us to assemble the eccentric phase from the concentric phase and execute the movement at different contraction velocities (Jerez-Mayorga et al, 2019Rodriguez-Perea et al, 2019Soriano-Maldonado et al, 2019;Fàbrica et al, 2020;Martinez-Garcia et al, 2020;Machado-Payer et al, 2020) . According to Dvir & Muller (2019) multiarticular isokinetic dynamometers (MID) such as FEMD can be applied validly and effectively to evaluate specific movement patterns, since there is no situation or action where only one muscle is working in isolation.…”