Background Single leg squat (SLS) is a widely used screening tool to assess lower limb dynamic control especially for knee valgus collapse. Dynamic function is determined from SLS through observation on knee alignment quality, and is proved related to lower limb, hip and core muscle strength,1–3 flexibilities and neuromuscular control patterns.4 On the other hand, the abovementioned items regarding muscle conditions are also well-known elements that contribute to physical fitness performance.5–9 Whereas there are limited studies on the relationship between SLS performance and lower limb fitness performance. Female youth soccer players were the selected population for this experiment, which was found to be most vulnerable to lower limb injuries due to gender anatomy and structure, for example ACL and ankle injuries.10–13
Objectives The present study investigated the correlation between subjective assessment on SLS with performance of three fitness elements in youth female soccer players.
Material and method A total of 36 youth female soccer players (age = 13.6 ± 1.1; height = 156.1 & plusmn;7.7 cm; weight = 48.7 ± 10.2 kg) was recruited to perform the SLS and three soccer-specific fitness tests regarding explosiveness, speed, agility after anthropometric measurements and warm-up. The SLS task was recorded in video in frontal plane view then rated by exercise specialist as “good” or “poor” by considering movement quality (Table 1) and joint alignments (Figure 1).14–16 The fitness performance was compared between the SLS rating “good” and “poor” group using t-test. Spearman correlation coefficients were generated between the fitness performance and SLS ratings.
Result Demographics of participants between 2 SLS groups (good/bad) were no significant difference in age (13.9 ± 1.0/13.5 ± 1.0, P = 0.462), height (156.3 ± 7.0/155.5 ± 9.2, P = 0.785) and weight (48.1 ± 10.0/49.9 ± 10.9, P = 0.640). There was no significant difference between SLS group rated “good” and “bad” performed by dominant leg regarding fitness performance (Table 1). And no significant correlation between SLS performance and any of the three fitness elements.
Conclusion SLS assessment by subjective rating is not capable of reflecting soccer-specific lower limb fitness level. Possible reason could be that current SLS rating method created ceiling effect and mask fitness level difference among players (ie not sensitive enough). Modification in SLS task eg multi-stage weight bearing, as well as increase objectivity of rating criteria may increase sensitivity. Also, comparison between SLS with other fitness parameters such as isometric strength, flexibility etc. could be explored in future studies.
Willson JD, Ireland ML, I Davis. Core strength and lower extremity alignment during single leg squats. Med Sci Sports Exerc 2006;38(5):945–52.
Crossley KM, et al. Performance on the single-leg squat task indicates hip abductor muscle function. Am J Sports Med 2011;39(4):866–73.
McCurdy K, et al. Comparison of lower extremity EMG between the 2-leg squat and modified single-leg squat in female athletes. J Sport Rehabil 2010;19(1):57–70.
Padua DA, Bell DR, MA Clark. Neuromuscular characteristics of individuals displaying excessive medial knee displacement. J Athl Train 2012;47(5):525–36.
Wisloff U, et al. Strong correlation of maximal squat strength with sprint performance and vertical jump height in elite soccer players. Br J Sports Med 2004;38(3):285–8.
Dobbs CW, et al. Relationship between vertical and horizontal jump variables and muscular performance in athletes. J Strength Cond Res 2015;29(3):661–71.
Marques MC, et al. Influence of Strength, Sprint Running, and Combined Strength and Sprint Running Training on Short Sprint Performance in Young Adults. Int J Sports Med 2015;36(10):789–95.
Castillo-Rodríguez A, et al. Relationship between muscular strength and sprints with changes of direction. The Journal of Strength & Conditioning Research, 2012;26(3):725–732.
Baldi M, et al. Repeated sprint ability in soccer players: associations with physiological and neuromuscular factors. J Sports Med Phys Fitness, 2016.
Le Gall F, Carling C, T Reilly. Injuries in young elite female soccer players an 8-season prospective study. Am J Sports Med 2008;36(2):276–284.
Faude O, et al. Injuries in female soccer players: a prospective study in the German national league. Am J Sports Med 2005;33(11):1694–700.
Myer GD, et al. The effects of generalised joint laxity on risk of anterior cruciate ligament injury in young female athletes. Am J Sports Med 2008;36(6):1073–80.
Hutchinson MR, Ireland ML. Knee injuries in female athletes. Sports Med 1995; 19(4):288–302.
Myer GD, et al. Three-dimensional motion analysis validation of a clinic-based nomogram designed to identify high ACL injury risk in female athletes. Phys Sportsmed 2011;39(1):19–28.
Stensrud S, et al. Correlation between two-dimensional video analysis and subjective assessment in evaluating knee control among elite female team handball players. Br J Sports Med 2011;45(7):589–95.
Whatman C, Hume P, Hing W. The reliability and validity of physiotherapist visual rating of dynamic pelvis and knee alignment in young athletes. Phys Ther Sport 2013;14(3):168–74.
- Single-leg squat
- Knee valgus
- Knee injuries
- Fitness performance
- Soccer fitness
- Female athletes
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