OPTIMIZED ANTHROPOMETRIC MODELLING OF THE FRONT SQUAT
The primary purpose of this thesis was to understand the relationship between the variation in athlete segment lengths (trunk, thigh, shank) and front squat depth as represented by maximum thigh segment rotation angle within the recommended guidelines. A validated segmental anthropometric model was used to simulate the effects of progressively altering thigh and trunk lengths on front squat depth. Both the thigh and trunk lengths were independently progressed through +/- 3 standard deviations, using the anthropometry collected from 41 athletes. This was done for simulated subjects of short (1.65 m for male and 1.55 m for females), average (1.82 m for male and 1.70 m for female), and tall (2.01 m for male and 1.87 m for females) statures. As thigh length increased, the ability to perform a full front squat (to a thigh depth of 180 degrees relative to the right horizontal) decreased. Conversely, as trunk length decreased, the ability to perform a full front squat decreased. The model was modified to progressively alter the thigh-to-trunk ratio from 0.8 to 1.2 for individuals of short, average and tall statures. Effects were similar for all heights for both males and females. Individuals with a thigh-to-trunk ratio above 1 were simulated to not be able to achieve a full front squat. This effect was greater in tall individuals, followed by average and then short. The ankle flexibility measured from the 41 athletes was run in simulations to determine its effects on front squat depth. For 25 of the athletes, the ankle flexibility did not allow their knees to pass the vertical plane of the toes. Flexibility constraints were removed from the model and the knees were moved to the vertical plane of the toes, 5 cm past, and 10 cm past. When the knees were allowed to move to the vertical projection of the toes, 8 athletes could not achieve a full front squat. When the knees were allowed to move 5 cm past the vertical projection of the toes, all athletes were predicted to be able to achieve a full front squat. When ankle flexibility was factored into the model, the results predicted that 16 athletes could not achieve a full front squat. The effects of ankle flexibility on front squat depth appeared to be influenced by the thigh-to-trunk ratio. Of the eight participants predicted not to be able to achieve a full front squat when the knees were allowed to reach the vertical projection of the toes, five had the largest thigh-to-trunk ratios. Athletes with a thigh-to-trunk ratio of 1 or greater may physically not be able to complete a full front squat according to the NSCA guidelines. It is however, more likely that the thigh-to-trunk ratio, which may limit the ability to achieve a full front squat, is significantly less than 1 when a trunk angle greater than 60 degrees is used. Furthermore, anterior knee translation initiated through rotation of the shank appears to be a strategy to maintain equilibrium at the end ranges of the front squat movement. It appears plausible that horizontal knee motion up to 5 cm past the vertical projection of the toes may allow athletes with large thigh-to-trunk ratios to reach full front squat depth and perhaps reduce loading on the low back. Additionally, ankle inflexibility may limit front squat depth.