The Oxygen Consumption and Metabolic Cost of Walking and Running in Adults With Achondroplasia

The disproportionate body mass and leg length of Achondroplasic individuals may affect their net oxygen consumption ([Formula: see text] O(2)) and metabolic cost (C) when walking at running compared to those of average stature (controls). The aim of this study was to measure submaximal [Formula: see text] O(2) and C during a range of set walking speeds (SWS; 0.56 – 1.94 m⋅s(-1), increment 0.28 m⋅s(-1)), set running speeds (SRS; 1.67 – 3.33 m⋅s(-1), increment 0.28 m⋅s(-1)) and a self-selected walking speed (SSW). [Formula: see text] O(2) and C was scaled to total body mass (TBM) and fat free mass (FFM) while gait speed was scaled to leg length using Froude’s number (Fr). Achondroplasic [Formula: see text] O(2TBM) and [Formula: see text] O(2FFM) were on average 29 and 35% greater during SWS (P < 0.05) and 12 and 18% higher during SRS (P < 0.05) than controls, respectively. Achondroplasic C(TBM) and C(FFM) were 29 and 33% greater during SWS (P < 0.05) and 12 and 18% greater during SRS (P < 0.05) than controls, respectively. There was no difference in SSW [Formula: see text] O(2TBM) or [Formula: see text] O(2FFM) between groups (P > 0.05), but C(TBM) and C(FFM) at SSW were 23 and 29% higher (P < 0.05) in the Achondroplasic group compared to controls, respectively. [Formula: see text] O(2TBM) and [Formula: see text] O(2FFM) correlated with Fr for both groups (r = 0.984 – 0.999, P < 0.05). Leg length accounted for the majority of the higher [Formula: see text] O(2TBM) and [Formula: see text] O(2FFM) in the Achondroplasic group, but further work is required to explain the higher Achondroplasic C(TBM) and C(FFM) at all speeds compared to controls. New and Noteworthy: There is a leftward shift of oxygen consumption scaled to total body mass and fat free mass in Achondroplasic adults when walking and running. This is nullified when talking into account leg length. However, despite these scalars, Achondroplasic individuals have a higher walking and metabolic cost compared to age matched non-Achondroplasic individuals, suggesting biomechanical differences between the groups.