Abstract
Competitive alpine skiers are subject to substantial risks of injury, especially concerning the anterior cruciate ligament (ACL). During “landing back weighted” episodes, hamstrings may partially counteract the anterior shear force acting on the tibia by eccentrically resisting the boot-induced drawer of the tibia relative to the femur. The aim of the present study was to provide novel descriptive data and sport-specific reference values on maximal eccentric hamstrings strength (MEHS) in competitive alpine skiers from youth to elite level, and to explore potential relationships with sex, age and biological maturation. 170 competitive alpine skiers were investigated: 139 youth athletes (51 females, 88 males; age: 13.8 ± 0.59 years) and 31 elite athletes (19 females, 12 males; age: 21.7 ± 2.8 years). MEHS was assessed by the (Vald Performance, Newstead, Australia). U15 female skiers presented lower MEHS compared to female elite skiers for both limbs (R = 210 ± 44 N vs. 340 ± 48 N, respectively, p < 0.001, and L = 207 ± 46 N vs. 303 ± 35 N, respectively, p < 0.001). Similarly, lower MEHS was observed in U15 male skiers compared to male elite skiers for both limbs (R = 259 ± 51 N vs. 486 ± 62 N, respectively, p < 0.001, and L = 258 ± 57 N vs. 427 ± 54 N, respectively, p < 0.001). Correlations between MEHS and chronological age were modestly significant only for the U15 group (r = 0.37 and p < 0.001). When the correlations for the U15 group were performed between MHES and maturity offset (obtained from the calculation of biological age, i.e., age at peak height velocity), statistical significance was reached by all the correlations run for 3 variables (Males < 0: r = 0.59, p < 0.0001; Males > 0: r = 0.70, p < 0.0001; and Females > 0: r = 0.46, p < 0.0001, start of maturity offset = 0). This cross-sectional description of MEHS in alpine skiers from youth to elite level highlights the importance of biological maturation for MEHS values in youth athletes and presents novel data that may offer insights into new approaches for injury prevention.
Highlights
Competitive alpine skiers are known to be subject to substantial risks of injury (Spörri et al, 2017)
When the correlations for the U15 group were performed between maximal eccentric hamstrings strength (MEHS) and maturity offset (Figure 5), statistical significance was reached by all the correlations run for 3 variables
The main findings were the following: (1) greater MEHS during Nordic Hamstrings Exercise (NHE) was observed by the elite skiers compared to the U15 group and greater strength was developed by male compared to female skiers for both groups
Summary
Competitive alpine skiers are known to be subject to substantial risks of injury (Spörri et al, 2017). Typical ACL-injury mechanisms include excessive knee joint compression, knee valgus and internal rotation, or a bootinduced anterior drawer of the tibia relative to the femur (Bere et al, 2011, 2013b; Jordan et al, 2017; Spörri et al, 2017). Physical aspects of the athlete have been suggested to be among the top 5 key injury risk factors in alpine ski racing (Spörri et al, 2012) and fitness parameters have been shown to be associated with injury risk (Raschner et al, 2012; Müller et al, 2017a). During typical ACL-injury mechanisms, such as the “landing back weighted” mechanism, hamstring muscles may act as an ACL-synergist by producing a posteriorly directed shear force to the tibia (i.e., by eccentrically resisting the boot-induced anterior drawer of the tibia relative to the femur while landing)
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