This experimental study will compare impact forces and metabolic cost in runners (N=20; ages 18-45 years, who already use a forefoot strike running gait) in two treadmill running test sessions (shod vs barefoot running)

Specific Aim 1: To identify if differences in metabolic cost exist between barefoot versus cushioned shod FM strikers during an acute bout of running exercise. Hypothesis: The metabolic cost will be higher in the cushioned shod runners with forefoot and midfoot strike compared to the barefoot runners.

Specific Aim 2: To identify if differences in peak impact forces exist between barefoot versus cushioned shod runners in forefoot-midfoot (FM) strikers.

Hypothesis: Peak impact forces will be higher in the barefoot runners with a forefoot and midfoot striking running style compared to the cushioned shod runners with a forefoot and midfoot striking running style.

Inclusion Criteria:

• trained runners with a running foot striking style of either initial forefoot or midfoot strike.
• run on average at least 20 miles/week
• be able to run for at least 20 minutes at one session
• free of any orthopedic limitation

Exclusion Criteria:

• history of lower extremity injury within the last 6 months prior to testing
• rear-foot strike running style
• does not run in a cushioned shoe on any occasion
• runs on average < 20 miles/week
• unable to run for 20 minutes or greater
• presence of any open wound or deformity on the feet which would prevent participant from running barefoot
• neurologic injury that would preclude normal running activity.

trained runners (men and women) who run with a FM strike (self-reported and verified in the laboratory).

Healthy young active adults

8 months