Isokinetic Performance of Knee Extensors and Flexors in Male Weightlifters

IntroductionWeightlifting is a sport in which the athlete attempts to lift a barbell loaded with weight plates (Chiu & Schilling, 2005; Larrat et al., 2007; Janz et al., 2008). This field of sport is widespread with its first international federation founded in 1905, recognized by the International Olympic Committee (IOC) in 1914 and became a permanent field of sport in the Olympic Games in Antwerp in 1920 (Stone et al., 2006). The main characteristic of the weightlifting is lifting the largest load possible in the shortest amount of time (Chiu & Schilling, 2005; Da Fonseca et al., 2007). Thus, athletes exhibit high rates of muscle activation, high peak power (Storey & Smith, 2012) and many musculoskeletal adaptations resulted by specific training (Chiu & Schilling, 2005). The startup movements (snatch) and the pitch (clean & jerk) are the movements that comprise the weightlifting practice (Janz et al., 2008; Storey & Smith, 2012). These movements are performed in phases that range from 3 to 5 seconds of duration and include an initial pull with knees straight leading the barbell to the level of the knees (start), followed by a transition period in which the torso moves to an upright position, and so the second pull occurs with an acceleration to raise the bar above the shoulder level and then extending the hips and knees bilaterally (clean & jerk) (Faigenbaum & McFarland, 2008; Storey & Smith, 2012). Weight lifting demands high technical levels since it requires controlled, quick and explosive combined movements (Faigenbaum & McFarland, 2008).When lifting weights, the biomechanical demands of the lower limbs joints change (Kipp et al., 2011) - the extension of the hips and knees increases acceleration and thus contributes to a correct and efficient execution of the movements (Gourgoulis et al., 2009). Regarding the knees, weightlifting plays a direct role to the knees involving their main extensor muscle groups and knee flexors, quadriceps and hamstrings respectively (Mafra et al., 2011; Storey & Smith, 2012). Therefore, the study of the knee joint muscle performance is extremely important for improving muscular performance and preventing the incidence of injuries by weightlifting athletes. Thus, the isokinetic evaluation, for being an evaluation method of great validity and reliability, may be used in order to verify muscular performance of these athletes (Bruyere et al., 2016). This study aimed to analyze, collecting information from a database, the muscular performance and the differences of the extensor and flexor muscles between dominant limb (DL) and non-dominant limb (NDL) in amateur male weightlifters.MethodsParticipantsThis is a quantitative, cross-sectional and retrospective study conducted at the Instituto de Medicina do Esporte e Ciencias Aplicadas ao Movimento Humano da Universidade de Caxias do Sul (IME-UCS) in the city of Caxias do Sul, Rio Grande do Sul, Brazil. It has been approved (protocol number 967.527) by the Ethical Research Committee of the Faculdade Cenecista Bento Goncalves (Bento Goncalves, Rio Grande do Sul, Brazil), and conducted according to the 2012 Law N°466 of the National Health Council and Helsinki Declaration, that approves the guidelines and rules for research involving human beings. The information provided by the IME-UCS' database concerning the concentric isokinetic evaluation of the knee extensor and flexor muscles from 10 male amateur weightlifting athletes were part of this study sample. The number of participants was conveniently established and, therefore, determined intentionally and not by probability according to the number of available evaluations in the IME-UCS's database. The evaluations in which the respective IME-UCS consent term had not been authorized by the athletes were excluded from this study. The mean age of the athletes was 28.10 (±0.49) years, mean height was 1.74 (±0.03) meters and mean weight was 100. …