PURPOSE: The reason for the presence of valgus knee angles during jumping in certain individuals is unclear. It appears to be more prevalent in females but has been observed in male subjects as well. Valgus knee position has been attributed to an increase in knee injury. The purpose of this study was to compare strength to body mass ratios (S:BM) and varus/valgus knee positions between males and females to determine if strength may be a factor in knee position during landing from various jumps. METHODS: Seventeen recreationally active females (age: 21.94 +/- 2.59 years; height: 167.32 +/- 5.20 cm; mass: 64.42 +/- 8.39 kg; % body fat: 26.89 +/- 6.26; squat 1RM: 66.18 +/- 19.47 kg; S:BM: 1.03 +/- 0.28) and thirteen recreationally active males (age: 21.69 +/- 1.65 years; height: 176.85 +/- 7.26 cm; mass: 72.39 +/- 9.23 kg; % body fat: 13.15 +/- 5.18; squat 1RM: 115.77 +/- 30.40 kg; S:BM: 1.59 +/- 0.31) performed a one repetition maximum in the squat to 90 degrees on knee flexion (1RM) and 3 of each of the following jumps: counter-movement jump (CMJ), 30 cm drop jump (DJ30), 45 cm drop jump (DJ45) and 60 cm drop jump (DJ60). Knee varus/valgus positions were analyzed through videography, concentric forces were collected from a force plate, and body composition for (S:BM) and squat to fat-free mass (S:FFM) were analyzed by dual energy X-ray absorptiometry. RESULTS: Significant differences were found between male and female 1RM (p = 0.000), male and female squat to body mass ratio (p = 0.000), and male and female S:FFM (p = 0.002). Significant differences were found between male and female knee varus/valgus positions, with females being relatively more valgus, during maximum flexion (MF) of the right leg in the CMJ (p = 0.004), DJ30 (p = 0.000), DJ45 (p = 0.000) and DJ60 (p = 0.000). The left leg exhibited the same pattern between males and females in the CMJ (p = 0.001), DJ30 (p = 0.002), DJ45 (p = 0.001) and DJ60 (p = 0.003). Peak concentric force data was only found to be significant between males and females at CMJ (p = 0.002), but not at DJ30 (p = 0.152), DJ45 (p = 0.176), or DJ60 (p = 0.119). Correlations between knee varus/valgus position and S:BM for all for jumps displayed moderate relationships (CMJ, r = 0.445; DJ30 r = 0.448; DJ45 r = 0.449; DJ60 r = 0.439). CONCLUSIONS: In conclusion, males and females have significantly different lower body strength levels and knee varus/valgus position when landing from jumps. Practical Applications: The discrepancy in strength level could be an important factor in knee varus/valgus position when landing. By increasing strength levels, an individual could possibly reduce their likelihood of knee injury from knee valgus landings.
(C) 2011 National Strength and Conditioning Association