Abstract
The disproportionate body mass and leg length of Achondroplasic individuals may affect their net oxygen consumption (O2) and metabolic cost (C) when walking at running compared to those of average stature (controls). The aim of this study was to measure submaximal O2 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). O2 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 O2TBM and O2FFM 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 CTBM and CFFM 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 O2TBM or O2FFM between groups (P > 0.05), but CTBM and CFFM at SSW were 23 and 29% higher (P < 0.05) in the Achondroplasic group compared to controls, respectively. O2TBM and O2FFM correlated with Fr for both groups (r = 0.984 – 0.999, P < 0.05). Leg length accounted for the majority of the higher O2TBM and O2FFM in the Achondroplasic group, but further work is required to explain the higher Achondroplasic CTBM and CFFM 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.
Highlights
Achondroplasia is a condition identified by a disproportionate shorter limb length relative to torso length compared to age matched average statured groups, hereafter referred to as ‘controls’ (Hoover-Fong et al, 2007)
Only 50% of the Achondroplasia group managed to obtain steady state running at 2.50 m·s−1 and only 20% maintained steady state running at 2.78 m·s−1
Achondroplasic running CFFM was, on average, 18% higher at all running speeds compared to controls (P < 0.05, Figure 1D)
Summary
Achondroplasia is a condition identified by a disproportionate shorter limb length relative to torso length compared to age matched average statured groups, hereafter referred to as ‘controls’ (Hoover-Fong et al, 2007). Increased stride frequency is observed in proportionally shorter statured groups compared to taller individuals during walking and running at the same speeds (Minetti et al, 1994). This in turn leads to a higher V O2 in the shorter groups at set walking speeds (Rowland and Green, 1988). To the authors’ knowledge though, there are no data pertaining to the measurement of V O2 in Achondroplasic individuals during incremental exercise let alone the scaling of V O2 during incremental exercise
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