Publication Date


Date of Final Oral Examination (Defense)


Type of Culminating Activity


Degree Title

Master of Science in Kinesiology, Biophysical Emphasis



Major Advisor

Tyler N. Brown, Ph.D


Clare K. Fitzpatrick, Ph.D


Shawn R. Simonson, Ed.D.


Introduction: During military activities, soldiers are often required to run at a fixed cadence with body borne load, but these loads purportedly increase leg stiffness, leading to increased risk of musculoskeletal injury. Yet, to date, it is unknown how altering stride length when running with body borne load affects lower limb stiffness for males and females. Purpose: To quantify leg stiffness, and lower limb joint (hip, knee and ankle) stiffness for males and females using different stride lengths to run with body borne loads of 20 kg, 25 kg, 30 kg, and 35 kg. Methods: Twenty-seven (17 males and 10 females) participants (age: 21.2 ± 2.3 years, height: 1.7 ± 0.1 m, and weight: 75.5 ± 11.3 kg) had leg and joint stiffness quantified while running at 4 m/s with four load conditions (20, 25, 30, and 35 kg). With each load condition, participants performed three run trials using either: their preferred stride length (PSL) and strides that are 15% longer (LSL) and shorter (SSL) than their PSL. Statistical Analysis: Leg and hip, knee, and ankle stiffness were submitted to a RM ANOVA to test the main effect and interaction of load (20, 25, 30, and 35 kg), stride length (PSL, PSL+15%, and PSL-15%), and sex (male vs female). Results: Body borne load increased leg stiffness (P=0.006). Male participants decreased leg stiffness as stride lengthened from SSL to PSL and PSL to LSL (P=0.026; P0.05). Body borne load increased peak vGRF (PP=0.010; P=0.011), while females only increased peak vGRF between PSL and LSL (PPP=0.013) stiffness increased with the addition of body borne load, but load had no significant effect on hip stiffness (P=0.723). Increasing stride length significant decreased ankle stiffness (P=0.003), but had no effect on hip (P=0.661) or knee (P=0.170) stiffness. Sex had no significant effect on hip (P=0.880), knee (P=0.234), or ankle (P=0.081) stiffness. Conclusion: Running with body borne load increased leg stiffness and potential risk of musculoskeletal injury. But, only male participants decreased leg stiffness and injury risk with longer strides. Both the knee and ankle increased joint stiffness, and risk of musculoskeletal injury with the addition of body borne load. The ankle, however, decreased joint stiffness with longer strides.