Relation between Muscle Force of Knee Extensors and Flexor Muscles and Sleep Quality of Women Soccer Players: A Pilot Study

Physical performance in sport performance such as football is influenced by sleep quality, but there are only a few studies about this and the behaviour of muscle force at knee flexors and extensors. The aim of this study is to make an analysis of sleep, an analysis of muscle force parameters (flexors and knee extensors), and a study of the correlation between sleep quality and muscle force. The study includes 18 junior women footballers, average age 14.75 years old, who participated in a training programme of 90 min, three times/week. The evaluation includes sleep quality evaluation using the sleep quality scale (SQS), sleepiness evaluation using the Cleveland Adolescent Sleepiness Questionnaire (CASQ), and muscle force evaluation using dynamometry for knee flexor and extensor muscles. We recorded maximal muscle force, medium maximal muscle force, and duration of maintained muscle force. We observed that more than 83% of subjects scored below 50% on the maximal SQS score and all participants scored less than 40 points (50%) on the CASQ’s maxim score, meaning a small level of sleepiness. With regard to muscle force, left–right symmetry for medium maximal force shows a predominance of the right-hand side and the value was 1.64%, for knee extensors and for knee flexors the difference was 7.58%, meaning that for knee extensors the symmetry is better than that of knee flexors. Statistical analysis regarding muscle parameters shows that there are no significant statistical differences between the left- and right-hand sides. Because the duration of the maintained maximal muscle force could indicate muscle fatigue, we observed that there was no link, and that sleep quality or sleepiness do not influence muscle fatigue. Our research concludes that muscle asymmetry of the left–right side of knee extensor and flexor muscles is minimal and does not correlate with sleep quality or sleepiness. There is no statistical correlation between muscle force parameters and sleep quality.