Reduced Vastus Medialis/Lateralis EMG Ratio in Volleyballers with Chronic Knee Pain on Sports-Specific Surfaces: A Pilot Study

Abstract

Background: Even though chronic knee pain is common in volleyball, neuromuscular imbalance as a potential risk factor has not been investigated in volleyball-specific tasks. The aim of the study was to compare neuromuscular control between healthy and injured players in a clinical jump test and a volleyball-specific jump task in real field conditions. Methods: Six athletes with knee pain and nine controls were included. Surface electromyographic data were recorded from the mm. vastus medialis (VM) and lateralis (VL) of both legs. VM/VL activation ratio was calculated from countermovement jump (CMJ) and volleyball spike indoors and on two beach surfaces. Results: All subjects had pain in the leading leg. Mann–Whitney U Test (M-W-U Test) revealed a significantly lower VM/VL ratio of the leading leg (always affected) of the injured compared with that of the healthy control group for the CMJ and spike jump on all three grounds. Bland–Altman analysis revealed low bias and low difference in standard deviation for the injured leg but high values for the uninvolved leg and healthy controls between tasks and grounds. These results could indicate that neuromuscular control might not adapt too well to different movement tasks and grounds in the injured leg. Conclusion: Athletes with chronic knee pain might have lower VM/VL ratios than controls independent from movement task and ground. Neuromuscular control in injured athletes might be less adaptable to new circumstances. The results of neuromuscular control in laboratory settings might be applicable to field conditions in injured legs but not healthy ones.

Vertical Jump Kinetic Parameters on Sand and Rigid Surfaces in Young Female Volleyball Players with a Combined Background in Indoor and Beach Volleyball

“…In agreement with past reports [ 2 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 37 , 38 ], h JUMP was higher on a RJS compared to SJS. Although this is not statistically relevant for all jump results yet, it is attributed to the low sample size, since only large effect sizes and not small or moderate effect sizes in a small population lead to a statically relevant result.…”

“…A vast amount of information on the decreased h JUMP on sand (SJS) compared to a rigid (RJS) jumping surface exists in the literature for BV players [ 2 , 15 , 16 , 17 , 18 , 19 , 20 , 21 ]. The decreased h JUMP on a SJS compared to RJS is associated with a lower force and power outputs [ 2 , 17 , 18 , 19 ] due to the less stiff surface and larger friction compared to indoor sport surfaces [ 15 ].…”

“…However, volleyball-specific training on a SJS during the indoor volleyball off-season resulted in higher physical fitness, such as higher endurance of quadriceps and calf muscles [ 22 ], as well as in higher jump height in SQJ and CMJ on both surfaces [ 22 ], and in the spike jump on a RJS [ 23 ]. Furthermore, there is evidence that CMJs on a RJS are not only useful to gain information regarding performance on a SJS, but also in relation to diagnosing neuromuscular imbalances in players with a mixed indoor volleyball and BV sport background for the spike jump on a SJS [ 16 ].…”