25 Jun 2021

Impact of COVID-19 on eccentric muscle strength in soccer players

Dr. James L. Nuzzo
Head of Exercise Science Research at Vitruvian
Certified Strength & Conditioning Specialist

The COVID-19 global pandemic has impacted life in many ways, including the ability to participate in sports and exercise.

In a recent study, sports scientists from Spain examined if home confinement from COVID-19 has impacted eccentric muscle strength of the hamstring muscles in 30 semi-professional soccer players. Their interest in the topic stemmed from knowledge that soccer players often experience hamstring injuries and that lower eccentric hamstrings strength sometimes correlates with increased risk of hamstrings injury. Thus, if soccer players experience reduced eccentric hamstrings strength due to home confinement, they might be at increased risk for injury when they return to play. 

To determine if eccentric strength of the hamstrings muscle decreases with confinement, the researchers measured it using the Nordic hamstring test. The Nordic hamstring test requires the athlete to position their knees on the floor with an upright torso, and then bend their torso forward as slowly as possible with their hands across their chest. As the player leans forward, their hamstrings are stretched while producing force (i.e., eccentric contraction) and the player catches themselves on the floor once they can no longer control the eccentric lowering. Because the soccer players were confined to home, the researchers devised a unique way to measure hamstrings muscle strength. They had players place their mobile phones at a set distance away from their bodies to video record their performance on the Nordic hamstrings test. From the video, the researchers could determine the Nordic break point angle and estimate hamstrings muscle strength. The strength assessments occurred 14, 28, and 49 days after confinement.

Eccentric muscle strength decreased with confinement. After 28 days of confinement, muscle strength was 8% lower than after 14 days of confinement. After 49 days of confinement, muscle strength was 14% lower than at 14 days of confinement. The reductions in strength occurred even though the players were performing muscle-strengthening exercises throughout confinement.

The results illustrate how home confinement impacts physical fitness. Confinement leads to decreased hamstrings muscle strength in soccer players. This decrease in eccentric strength means players will need to participate in focused post-confinement training to regain their strength. Alternatively, the players might benefit from more intense or more frequent eccentric training while in confinement to prevent such losses in strength.


Training with a Vitruvian device can help athletes and non-athletes maintain muscle strength during confinement. The device stacks on heavy resistances, it has a library of exercises for the hamstrings muscles, and it has an eccentric training mode that provides resistance only during the eccentric phase of the exercise. Eccentric training mode on the V-Form or Trainer+ allows athletes to use resistances that are heavier than what can typically be accomplished with free weights. To complete eccentric hamstring training with the V-Form or Trainer+:

  1. attach the bar
  2. select the “Romandian deadlift (RDL)” exercise
  3. select “eccentric only” mode
  4. select the desired resistance and number of repetitions 
  5. set movement range of motion for the exercise with the first 3 calibration repetitions
  6. once the exercise begins, pause at the top of the movement to load the eccentric phase
  7. control the load slowly down to the bottom of the movement then let the resistance unload before lifting the bar back up
  8. repeat the movement until the desired number of repetitions have been completed


Moreno-Pérez V, et al. Effects of home confinement due to COVID-19 pandemic on eccentric hamstring muscle strength in football players. Scandinavian Journal of Medicine and Science in Sports 30: 2010-2012, 2020. DOI: 10.1111/sms.13768.

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