Operating length and velocity of human M. vastus lateralis fascicles during vertical jumping

Abstract

Humans achieve greater jump height during a counter-movement jump (CMJ) than in a squat jump (SJ). However, the crucial difference is the mean mechanical power output during the propulsion phase, which could be determined by intrinsic neuro-muscular mechanisms for power production. We measured M. vastus lateralis (VL) fascicle length changes and activation patterns and assessed the force–length, force–velocity and power–velocity potentials during the jumps. Compared with the SJ, the VL fascicles operated on a more favourable portion of the force–length curve (7% greater force potential, i.e. fraction of VL maximum force according to the force–length relationship) and more disadvantageous portion of the force–velocity curve (11% lower force potential, i.e. fraction of VL maximum force according to the force–velocity relationship) in the CMJ, indicating a reciprocal effect of force–length and force–velocity potentials for force generation. The higher muscle activation (15%) could therefore explain the moderately greater jump height (5%) in the CMJ. The mean fascicle-shortening velocity in the CMJ was closer to the plateau of the power–velocity curve, which resulted in a greater (15%) power–velocity potential (i.e. fraction of VL maximum power according to the power–velocity relationship). Our findings provide evidence for a cumulative effect of three different mechanisms—i.e. greater force–length potential, greater power–velocity potential and greater muscle activity—for an advantaged power production in the CMJ contributing to the marked difference in mean mechanical power (56%) compared with SJ.

Do Stretch-Shortening Cycles Really Occur in the Medial Gastrocnemius? A Detailed Bilateral Analysis of the Muscle-Tendon Interaction During Jumping

“…This is consistent with previous studies on the medial gastrocnemius muscle during walking, running, and bilateral jumping Lichtwark and Wilson, 2006;Farris and Sawicki, 2012;Aeles et al, 2018) and with results from other triceps surae muscles such as the lateral gastrocnemius and soleus (Cronin and Finni, 2013;Lai et al, 2015). In a recent study on the muscle-tendon interaction in the vastus lateralis muscle, also no active stretching of the muscle fascicles was found during a squat jump (Nikolaidou et al, 2017). In the study by Nikolaidou et al (2017), the fascicles did lengthen in the counter-movement jump, however, this occurs prior to activation of the muscle, as can be seen from the EMG data, and is therefore not considered an active SSC.…”

“…In a recent study on the muscle-tendon interaction in the vastus lateralis muscle, also no active stretching of the muscle fascicles was found during a squat jump (Nikolaidou et al, 2017). In the study by Nikolaidou et al (2017), the fascicles did lengthen in the counter-movement jump, however, this occurs prior to activation of the muscle, as can be seen from the EMG data, and is therefore not considered an active SSC. In other studies that have shown stretching of the muscle fascicles in the medial gastrocnemius and soleus, vastus laterlias, and tibialis posterior, et al, 2017).…”

“…However, it is likely that the peak ankle dorsiflexion angle during ground contact is close to the maximal range of motion for this joint, limiting further stretching of the muscle-tendon unit. Extending the knee more would allow for further stretching in the muscle-tendon unit of the medial gastrocnemius, but would come at the cost of less stretching of the MTUs of the knee extensors, which have also been shown to store and release significant amounts of elastic energy in the serieselastic element (Nikolaidou et al, 2017). On the other hand, at ground contact, the ankle was already in a more dorsiflexed position compared to the bilateral pre-hop squat jump while the initial knee joint angle is very similar (Aeles et al, 2018).…”

Gastrocnemius Medialis and Vastus Lateralis in vivo muscle‐tendon behavior during running at increasing speeds

“…Indeed, as shown in Figure 1, the main length changes of the VL MTU were primarily associated with changes of the series‐elastic elements of the VL (patellar and quadriceps tendon complex). This SEE behavior allows the fascicles to take advantage of the high force‐length‐velocity potentials during the active phase of the stance phase where the VL muscle generates force 23,38 …”

Simple Muscle Architecture Analysis (SMA): An ImageJ macro tool to automate measurements in B-mode ultrasound scans

“…The images generated by this method are complex, and require a great deal of time and effort from practitioners to interpret and extract meaning from them. In recent years, efforts have been made to automate parts of this process [5][6][7][8][9][10]. However, these efforts have been fragmented, and suffer from a number of limitations: they often focus on analysing a single parameter of interest; most publications do not reveal specific details of how to implement the method; some methods rely on software that require expensive licence fees; the majority of methods are only semi-automated, requiring manual, subjective interpretation of at least some images; and often tracking methods involve complex mathematics and require computer programming experience.…”