July 2019

Skipping Tops Running for Knee Joint Contact Forces and Metabolic Costs

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Running’s high rate of sport-related injury is a prime driver of reduced exercise participation, despite its bountiful health benefits. Skipping—that childhood symbol of carefree whimsy—presents a lot like running, but when compared to running, provides unique benefits: shorter steps, reduced vertical ground reaction forces (GRFs), and lower knee extensor torques. Understanding these differences, researchers from North Carolina sought to determine if skipping would have lower tibiofemoral and patellofemoral joint contact forces. Given that previous studies had shown skipping has a high metabolic cost, they also looked to determine what role the larger vertical displacement played in skipping’s overall metabolic cost.

The researchers recruited 20 young, healthy volunteers and then had them run and skip on an instrumented treadmill at a predetermined rate of 2.68 m/s.

Using musculoskeletal modeling with GRF and 3D kinematic data as well as oxygen consumption to determine metabolic cost, the researchers found that, when compared to skipping:

Peak and impulse tibiofemoral loads were 30% higher when running (both per step and per kilometer).

Peak and impulse patellofemoral loads were 98% higher when running (both per step and per kilometer).

As for energy expenditure and those prior studies, the researchers also found that 30% more calories were burned when skipping than previously reported. Additionally, vertical displacement when skipping was nearly double compared to running and that displacement correlated with higher metabolic cost. The authors attributed the lower joint loads to the shorter steps, and the larger vertical displacement was associated with the greater metabolic cost.

The authors concluded that skipping presents an attractive exercise alternative with added increased aerobic benefits.

Source: McDonnell J, Zwetsloot KA, Houmard J, DeVita P. Skipping has lower knee joint contact forces and higher metabolic cost compared to running. Gait Posture. 2019;70:414-419.

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