Date Approved


Graduate Degree Type


Degree Name

Engineering (M.S.E.)

Degree Program

School of Engineering

First Advisor

Dr. Wendy Reffeor

Second Advisor

Dr. Kyle Barnes

Third Advisor

Dr. Shirley Fleischmann

Academic Year



The materials used in running shoe midsoles are viscoelastic. Following a training session, a period of rest is required for the midsoles to undergo shape recovery and regain their energy absorption capability. It is common to think that a shoe will need two days of rest following a run to be adequately recovered in order to minimize the risk of running related injury and to maximize shoe performance while also maximizing the useful life of the shoe. Mechanical aging studies were done to investigate the effects of intermittent recovery periods on performance of an athletic shoe, the Nike Pegasus Turbo II. Aging was done using a hydraulic tensile testing machine to produce cyclic loading using a sinusoidal waveform with peak force of 1600 N and frequency of 1.42 Hz. Two test protocols were used with nine specimens each; the first incorporated intermittent rest periods of 23 hours between aging sessions of 10.55 km, and the second had no rest period while aging to a distance of 42.2 km, or 26.2 miles – a marathon. Different lengths of recovery periods (1, 2, or 3 days) were then assessed following the protocol aging tests; finally, performance was measured after each varied recovery period. Also, shape recovery of the midsole was tracked during each rest period using a dial indicator.

The results of the aging study show that rest does have an impact on midsole performance only after approximately 15.83 km. No trend was seen among the 1, 2, or 3 days of rest following the protocol aging which may indicate that adequate recovery of energy absorption capability is achieved before 24 hours. This is supported by the recovery curves which show that 90% of the shape recovery for the rested shoe sample occurs within 7.28 hours and for the non-rested shoe sample occurs on average at 12.52 hours.

Available for download on Sunday, May 26, 2024

Included in

Engineering Commons