Effects of different oral instructions on kinematic and kinetic parameters during drop vertical jump

The acute effect of verbal instructions on performance and landing when dropping from different heights: the ground reaction force-time profile of drop vertical jumps in female volleyball athletes

Introduction

The drop vertical jump (DVJ) is extensively utilized for conditioning and evaluating physical performance, as well as reducing the likelihood of injury by enhancing joint stability through the coactivation of muscles acting on the joint. The execution of DVJ can be controlled by verbal instructions and evaluated by the vertical ground reaction force (vGRF)-time profile.

Methods

Our hypothesis was that varying verbal instructions could have an impact on the DVJ's parameter, thereby optimizing vertical performance and minimizing the impact during landing in young female volleyball players. Sixteen female volleyball players volunteered to participate in this study (age: 21.3 ± 2.6 years; stature: 1.66 ± 0.1 m; body mass: 62.0 ± 8.1 kg and BMI: 22.2 ± 1.8). They executed DVJs following verbal instructions ranging from "jump as high as possible" (1A), "jump as quickly as possible" (2A), "jump as high as possible and during the landing attempt to dampen the impact at ground contact" (1B), and "jump as high as quickly as possible and during the landing attempt to damp the impact at ground contact" (2B). The reactive strength index (RSI), vGRF (1st and 2nd peaks), and flight time (FT) were evaluated.

Results

The verbal instructions 1A improved the FT and the first peak of the vGRF (P < 0.05), whereas 2A the RSI (P < 0.05). On the contrary, "the damping" required in the 1B, and 2B verbal instruction reduced the 2nd peak of vGRF (P < 0.05), without altering the task required during the jump (P < 0.05).

Discussion

The instructions provided for the final landing (the second peak of vGRF) have the potential to enhance safety by reducing the peak of vGRF without affecting the performance required during the jump. When designing DVJ training, coaches or kinesiologists must consider the use of verbal instructions to induce specific adaptation over time.

Clinical relevance

The present study supports the use of specific verbal instructions to reduce impact forces in landing and injury risk.

Effects of external verbal cueing on countermovement rebound jump performance

This study examined the effects of three external verbal cues on countermovement rebound jump (CMRJ) performance. Twenty-five recreational athletes completed nine jumps with distinct height, velocity and combined cue focus. A general linear model analysis of variance was used to evaluate systematic bias between conditions (p < 0.05). The height and velocity cues significantly altered jump height and contact times in both jumps during the CMRJ, respectively (p ≤ 0.002). The combined cue significantly reduced contact time while increasing leg stiffness compared to the height cue (p ≤ 0.038). It also increased jump height compared to the velocity cue (p ≤ 0.005) in both jumps, resulting in the highest explosive power and reactive strength values among all conditions. Furthermore, the combined cue enhanced the positive ankle contribution compared to the height cue (p = 0.020) and increased positive hip and negative knee joint work compared to the velocity cue (p ≤ 0.040) in the second jump of the CMRJ. These findings advise practitioners to use the height cue to maximise jump height, the velocity cue to minimise contact times and the combined cue to maximise explosive power and reactive strength.

Influence of neoprene ankle orthoses on dynamic balance during a vertical jump in healthy individuals and with sprain history: A cross-sectional study

INTRODUCTION

A sprain describes an excessive amount of force or strain on a ligament, which may or may not lead to its rupture. Orthoses are among the most common modalities prescribed as a conservative treatment for ankle instability and sprain.

OBJECTIVE

We aimed to analyse the effect of neoprene orthosis on the balance and functionality of healthy individuals and volunteers with lateral ankle sprains METHODS: We evaluated 12 healthy volunteers (control group) and 12 volunteers diagnosed with a sprain and/or instability (patient group). A total of 14 men and 10 women participated in the study, with an average age of 26.15 (± 4.40) years. The volunteers' tasks consisted of performing vertical bipodal and unipodal jumps on a force platform, which were recorded in a video from the lateral view of the lower limb for posterior evaluation of the knee and ankle angles. Mann-Whitney and Wilcoxon tests were used for comparisons, considering p < 0.05 level of significance.

RESULTS

The control group presented a decrease in ground reaction force when using Orthosis during the bipodal jump (p < 0.05). A decrease in anteroposterior force displacement was also observed in the left unipodal jump (p < 0.01). The patient group presented an increase in force and moment of medial-lateral displacement for both bipodal (p < 0.02) and left unipodal jumps with Orthosis (p < 0.02). A kinematic analysis showed that the control group presented the smallest knee flexion angle (p < 0.01), while the patient group presented the smallest dorsiflexion ankle angle in the bipodal jump when using orthosis (p < 0.01).

CONCLUSION

We concluded that orthosis had influence on individuals' balance and joint angles. In healthy individuals presented better balance with and without orthosis and greater flexion with orthosis in the bipodal jump, regarding to the patient group presented smaller oscillations in the unipodal jump with orthosis and showed smaller knee flexion and ankle dorsiflexion.

Neuromuscular Strategies in Stretch-Shortening Exercises with Increasing Drop Heights: The Role of Muscle Coactivation in Leg Stiffness and Power Propulsion

When applying drop jump exercises, knowing the magnitude of the stimulus is fundamental to stabilize the leg joints and to generate movements with the highest power. The effects of different drop heights on leg muscles coactivation, leg stiffness and power propulsion were investigated in fifteen sport science students. Drop jumps from heights of 20, 30, 40, 50, and 60 cm in a random order were performed on a force platform. During each drop jump, the ground reaction force, knee angle displacement, and synchronized surface-electromyography root-mean-square (sEMG_RMS) activity (vastus lateralis, VL; vastus medialis, VM; rectus femoris, RF; biceps femoris, BF; tibialis anterior, TA and lateral gastrocnemius, LG) were recorded. The coactivation in the pre-contact phase, between VL and BF, VM and BF as well as RF and BF, was dependent on the drop height (p < 0.01; effect size (ES) ranged from 0.45 to 0.90). Leg stiffness was dependent on the drop height (p < 0.001; ES = 0.27-0.28) and was modulated by the coactivation of VM-BF (p = 0.034) and RF-BF (p = 0.046) during the braking phase. Power propulsion was also dependent on the drop height (p < 0.001; ES = 0.34); however, it was primarily modulated by the coactivation of LG-TA during the braking phase (p = 0.002). The coactivation of thigh muscles explains leg stiffness adjustments at different drop heights. On the contrary, the coactivation of shank muscles is mostly responsible for the power propulsion.