Impact Attenuation And Kinetic Characteristics Of Cross Training Shoes In Landing And Jumping Activities

Abstract

Very few footwear studies have examined athletic shoes designed for sports other than running. Cross-training footwear is designed to meet needs of a variety of sports and sport training environments with key features that include generating power for performance and attenuating impacts for injury prevention. PURPOSE To examine kinetic characteristics of impact attenuation in landing and power generation in jumping of four different cross training shoes. METHODS Ten healthy male recreational athletes (age:21.5±2.5 yrs) performed five step-off landing trials and five maximum vertical jumping trials in each of four cross-training shoes (from three leading footwear manufacturers). Right sagittal kinematic data (120 Hz), ground reaction forces (GRF,1200 Hz), and forehead and distal tibia accelerations (ACC, landing only) were measured simultaneously. The landing height was determined individually based upon potential energy of a “mid-size” person (80 kg) landing from a 0.6 m height. Material tests were performed on selected sizes of each shoe model.A one-way repeated measures ANOVA and post-hoc comparisons (p < 0.05) were performed on selected variables. RESULTS The results from the landing trials showed that Shoes A (23 N/kg) and B (26 N/kg) had significantly smaller forefoot peak GRF than Shoes C (29 N/kg) and D 28 N/kg). Shoes A (2274 N/kg/s) and B (2630 N/kg/s) also showed lower loading rate associated with the forefoot contact than Shoes C (3316 N/kg/s) and D (3336 N/kg/s). No significant changes were seen in ACC data. The jumping GRF results normalized to the individual jump height indicated significantly greater peak power for Shoes C (50 Wm/kg) and D (51 Wm/kg) compared to A (48 Wm/kg). Maximum peak GRF for Shoe D (16 Nm/kg) was greater than Shoe A (15 Nm/kg). In addition, kinematic data showed not clear trends in landing or jumping trials. The material testing indicated that Shoes A and B had the smallest forefoot stiffness values (9.2 and 9.6 N/mm) compared to Shoe C and D (18.0 and 12.7 N/mm) obtained in a fixibility test. Energy loss for Shoes A and B (41%and 43%) were greater than Shoes C and D (33 and 35%). CONCLUSIONS The results suggested that the Shoes A and B showed slightly better forefoot impact attenuation properties. Shoe D and C demonstrated better jumping performance than Shoe A. But better performance may come at a price of decreased cushioning.