Cadence 180, magic number? How they come up with this?

12TH NOVEMBER 2015 BY MICK WILKINSON
Harvard research supports BTR coaching wisdom

Professor Dan Lieberman’s latest publication supports the Born to Run coaching philosophy

Lee Saxby’s Born to Run coaching system emphasizes the detrimental effects of over stride both on injury risk and on running economy. Lee made the connection between over stride and running rhythm / stride frequency a long time ago and subsequently made rhythm the second priority in his ‘posture-rhythm-relaxation’ movement mantra.

About the study

The study examined the relationships between stride frequency, over stride, braking forces, peak-impact forces and loading rates, and the energy cost of running at a fixed speed (3.0 m/s) in 14 experienced runners. Participants were asked to run on a treadmill with stride frequencies of 75, 80, 85, 90 and 95 strides/min. Ground-reaction forces, lower-extremity joint angles and the metabolic cost of running were measured.

What the study showed

• For every increase of 5 strides/min, the energy cost of swinging the leg forwards (estimated from maximum-hip-flexion moment) increased by 5.8%, and over stride (landing position of the foot relative to the hip) decreased by 5.9%
• Larger over stride associated with higher braking (backwards oriented) forces and with higher peak-vertical-ground-reaction forces
• Metabolically-optimal (least costly) stride frequency was around 85-90 strides/min (170-180 steps/min)

Take home message

Increased stride frequency (within optimal range) decreases over stride and, in turn, decreases braking force and peak-vertical-impact force that are related to injury risk. In addition to reduced braking and impact forces, stride frequency within the BTR recommended range decreases the metabolic cost of running.

References

Lieberman, D.E., Warrener, A.G., Wang, J. and Castillo, E.R. (2015). Effects of stride frequency and foot position at landing on braking force, hip torque, impact peak force and the metabolic cost of running in humans. Journal of Experimental Biology, 218, 3406-3414.

Paper available HERE.



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