The effect of trunk-flexed postures on balance and metabolic energy expenditure during standing.
METHODS
This study analyzed force plate, kinematic, and metabolic energy data of 14 able-bodied subjects standing statically with upright and trunk-flexed postures.


OBJECTIVE
To explore the effect of trunk-flexed postures on balance and metabolic energy expenditure during standing.


BACKGROUND
Abnormal trunk posture often occurs in the presence of spinal deformities, such as lumbar flatback. It is unclear whether alterations in trunk posture affect energy expenditure and the location of the body's center of mass in the transverse plane (BCOMtrans) during standing.


METHODS
Kinematic, kinetic, and energy expenditure data were collected with upright trunk alignment and with 25 degrees +/- 7 degrees and 50 degrees +/- 7 degrees of trunk flexion from the vertical. The mean location of the BCOMtrans was estimated from the net center of pressure (COP), which is a weighted average of the COP beneath both feet.


RESULTS
The fore-aft position of the net COP under the base of support was not significantly different between postures (P < 0.08). At each posture, the net COP was located 16% of the foot length anterior to the ankle joint centers. However, with increasing trunk flexion, there was a significant increase in oxygen consumption rate (P < 0.001 for all postures).


CONCLUSIONS
Compensatory actions, such as ankle plantarflexion and hip flexion, allowed the mean position of the net COP to remain within a narrowly defined region irrespective of trunk posture. Changes in muscle activity associated with a trunk-flexed posture and the associated compensations likely contributed to the increased energy expenditure.
Saha
Devjani
D
Northwestern University Prosthetics Research Laboratory & Rehabilitation Engineering Research Program, Department of Physical Medicine & Rehabilitation, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA. d-saha@northwestern.edu
Gard
Steven
S
Fatone
Stefania
S
Ondra
Stephen
S
D000328:Adult; D000843:Ankle Joint / Q000502:physiology; D001696:Biomechanical Phenomena; D004734:Energy Metabolism / Q000502:physiology*; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006621:Hip Joint / Q000502:physiology; D006801:Humans; D008297:Male; D009068:Movement / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D010101:Oxygen Consumption / Q000502:physiology; D004856:Postural Balance / Q000502:physiology*