Quadrupedal Locomotion-Respiration Entrainment and Metabolic Economy in Cross-Country Skiers.

Kevin Boldt,Anthony Killick,Walter Herzog

doi:10.1123/jab.2014-0243

Abstract

A 1:1 locomotion-respiration entrainment is observed in galloping quadrupeds, and is thought to improve running economy. However, this has not been tested directly in animals, as animals cannot voluntarily disrupt this entrainment. The purpose of this study was to evaluate metabolic economy in a human gait involving all four limbs, cross-country skiing, in natural entrainment and forced nonentrainment. Nine elite cross-country skiers roller skied at constant speed using the 2-skate technique. In the first and last conditions, athletes used the natural entrained breathing pattern: inhaling with arm recovery and exhaling with arm propulsion, and in the second condition, the athletes disentrained their breathing pattern. The rate of oxygen uptake (VO2) and metabolic rate (MR) were measured via expired gas analysis. Propulsive forces were measured with instrumented skis and poles. VO2 and MR increased by 4% and 5% respectively when skiers used the disentrained compared with the entrained breathing pattern. There were no differences in ski or pole forces or in timing of the gait cycle between conditions. We conclude that breathing entrainment reduces metabolic cost of cross-country skiing by approximately 4%. Further, this reduction is likely a result of the entrainment rather than alterations in gait mechanics.

Highlights

When quadrupedal animals transition from a trot to a gallop, they exhibit a very particular locomotion-respiration coupling, or entrainment, between their breathing and movement patterns[1]
Expired air was converted to standard temperature, pressure and dry (STPD) conditions, and analyzed to determine rate of oxygen consumption (V Rate of oxygen consumption (O2)), metabolic rate (MR) in calories consumed per minute, minute ventilation (V E), and respiratory exchange ratio (RER), the ratio between the rate of carbon dioxide produced (V CO2) and V O2
The primary finding of this study was that dis-entrained breathing was associated with a significant increase in V O2 compared to the entrained breathing condition

Summary

Introduction

When quadrupedal animals transition from a trot to a gallop, they exhibit a very particular locomotion-respiration coupling, or entrainment, between their breathing and movement patterns[1]. Animals exhale as they draw their forelimbs back and inhale as they extend their forelimbs This coupling typically presents as a 1:1 ratio between breaths and strides, where the animal breathes once every stride. When using a particular technique of cross country skiing, the two-skate ( known as V2 alternate or G4) technique, athletes move their skis in a skating motion while pushing with both poles simultaneously on every second ski plant (i.e. with either the left or the right ski) Using this distinctly four-limbed human gait, a natural breathing entrainment occurs with skiers inhaling as they recover the poles and exhaling as they push back with the poles[11]

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