The metabolic cost of walking on gradients with a waddling gait

Abstract

SUMMARYUsing open-flow respirometry and video footage (25framess -1 ), the energy expenditure and hindlimb kinematics of barnacle geese, Branta leucopsis, were measured whilst they were exercising on a treadmill at gradients of +7 and -7deg, and on a level surface. In agreement with previous studies, ascending a gradient incurred metabolic costs higher than those experienced on level ground at comparable speeds. The geese, however, are the first species to show an increased duty factor when ascending a gradient. This increased duty factor was accompanied by a longer stance time, which was probably to enable the additional force required for ascending to be generated. Contrary to previous findings, the geese did not experience decreased metabolic costs when descending a gradient. For a given speed, the geese took relatively shorter and quicker strides when walking downhill. This ʻchoppyʼ stride and perhaps a lack of postural plasticity (an inability to adopt a more crouched posture) may negate any energy savings gained from gravityʼs assistance in moving the centre of mass downhill. Also contrary to previous studies, the incremental increase in metabolic cost with increasing speed was similar for each gradient, indicating that the efficiency of locomotion (mechanical work done/chemical energy consumed) is not constant across all walking speeds. The data here suggest that there are species-specific metabolic responses to locomotion on slopes, as well as the established kinematics differences. It is likely that a suite of factors, such as ecology, posture, gait, leggedness and foot morphology, will subtly affect an organismʼs ability to negotiate gradients.

Geckos decouple fore- and hind limb kinematics in response to changes in incline

“…Geckos do not change the timing of limb movements on uphill surfaces compared to level (Table 1 ). This is drastically different to previous studies of inclined locomotion where significant increases in stride time [ 24 , 57 ] and duty factor [ 13 , 23 , 24 ] are evident. Duty factor often increases on uphill surfaces, allowing greater time in contact with the ground to provide the extra work required to move against gravity.…”

“…Remarkably swing time did decrease on the 45° decline condition from level in our study (Table 1 ). Reduction in swing time compared to level terrain has previously been noted in birds on inclines [ 23 , 68 ]. Shortening the swing time, whilst keeping stance time constant, could be a strategy to maintain relatively consistent peak forces, as well as provide enough time for producing an impulse that can generate work for going uphill, or absorb energy (negative work) when moving downhill.…”

Geckos decouple fore- and hind limb kinematics in response to changes in incline

“…Geckos do not change the timing of limb movements on uphill surfaces compared to level (Table 1 ). This is drastically different to previous studies of inclined locomotion where significant increases in stride time [ 24 , 57 ] and duty factor [ 13 , 23 , 24 ] are evident. Duty factor often increases on uphill surfaces, allowing greater time in contact with the ground to provide the extra work required to move against gravity.…”

“…Remarkably swing time did decrease on the 45° decline condition from level in our study (Table 1 ). Reduction in swing time compared to level terrain has previously been noted in birds on inclines [ 23 , 68 ]. Shortening the swing time, whilst keeping stance time constant, could be a strategy to maintain relatively consistent peak forces, as well as provide enough time for producing an impulse that can generate work for going uphill, or absorb energy (negative work) when moving downhill.…”

The metabolic cost of incline locomotion in the Svalbard rock ptarmigan (Lagopus muta hyperborea): the effects of incline grade and seasonal fluctuations in body mass

“…This method, however, relies on a difference between the regression slopes. In the present study, in common with findings in mice, crabs, quail and more recently geese, the MCoT did not differ upon incline locomotion in either season (Nudds and Codd, 2012;Taylor et al, 1972;Tullis and Andrus, 2011;Warncke et al, 1988). Applying the traditional approach to such data would therefore reveal no additional cost of lifting despite absolute energy expenditure values clearly being higher during incline locomotion.…”

“…Similar findings have been demonstrated in humans, although the curvilinear nature of metabolic cost during walking makes comparison with avian data problematic (Margaria et al, 1963). In the only avian studies to use solely walking gaits, quail on inclines of 4, 8 and 12deg shared a common slope and geese on inclines of 7deg showed no difference in MCoT compared with that on level ground (Nudds and Codd, 2012;Warncke et al, 1988). The results of both studies are in agreement with our findings, highlighting the importance of gait when measuring the energetic cost of locomotion.…”

The metabolic cost of walking on an incline in the Peacock (Pavo cristatus)

“…In a number of investigations, few kinematic parameter changes are found between horizontal and incline locomotion ( Eaton et al, 1995 ; Full & Tullis, 1990 ; Lees et al, 2013 ). In the present study, however, peacocks maintained higher DF’s on an incline than on the level ( Nudds & Codd, 2012 ). The increase in DF, and the decrease in 1/ t stance found when comparing level and incline movement ( Oldruitenborgh-Oosterbaan, Barneveld & Schamhardt, 1997 ), indicated that the increased cost of incline locomotion in the peacock was not influenced by a higher rate of muscle force development ( Kram & Taylor, 1990 ; Roberts et al, 1998 ).…”

Geckos decouple fore- and hind limb kinematics in response to changes in incline

“…Geckos do not change the timing of limb movements on uphill surfaces compared to level (Table 1 ). This is drastically different to previous studies of inclined locomotion where significant increases in stride time [ 24 , 57 ] and duty factor [ 13 , 23 , 24 ] are evident. Duty factor often increases on uphill surfaces, allowing greater time in contact with the ground to provide the extra work required to move against gravity.…”

“…Remarkably swing time did decrease on the 45° decline condition from level in our study (Table 1 ). Reduction in swing time compared to level terrain has previously been noted in birds on inclines [ 23 , 68 ]. Shortening the swing time, whilst keeping stance time constant, could be a strategy to maintain relatively consistent peak forces, as well as provide enough time for producing an impulse that can generate work for going uphill, or absorb energy (negative work) when moving downhill.…”

The metabolic cost of incline locomotion in the Svalbard rock ptarmigan (Lagopus muta hyperborea): the effects of incline grade and seasonal fluctuations in body mass

“…This method, however, relies on a difference between the regression slopes. In the present study, in common with findings in mice, crabs, quail and more recently geese, the MCoT did not differ upon incline locomotion in either season (Nudds and Codd, 2012;Taylor et al, 1972;Tullis and Andrus, 2011;Warncke et al, 1988). Applying the traditional approach to such data would therefore reveal no additional cost of lifting despite absolute energy expenditure values clearly being higher during incline locomotion.…”

“…Similar findings have been demonstrated in humans, although the curvilinear nature of metabolic cost during walking makes comparison with avian data problematic (Margaria et al, 1963). In the only avian studies to use solely walking gaits, quail on inclines of 4, 8 and 12deg shared a common slope and geese on inclines of 7deg showed no difference in MCoT compared with that on level ground (Nudds and Codd, 2012;Warncke et al, 1988). The results of both studies are in agreement with our findings, highlighting the importance of gait when measuring the energetic cost of locomotion.…”

The metabolic cost of walking on an incline in the Peacock (Pavo cristatus)

“…In a number of investigations, few kinematic parameter changes are found between horizontal and incline locomotion ( Eaton et al, 1995 ; Full & Tullis, 1990 ; Lees et al, 2013 ). In the present study, however, peacocks maintained higher DF’s on an incline than on the level ( Nudds & Codd, 2012 ). The increase in DF, and the decrease in 1/ t stance found when comparing level and incline movement ( Oldruitenborgh-Oosterbaan, Barneveld & Schamhardt, 1997 ), indicated that the increased cost of incline locomotion in the peacock was not influenced by a higher rate of muscle force development ( Kram & Taylor, 1990 ; Roberts et al, 1998 ).…”

Geckos decouple fore- and hind limb kinematics in response to changes in incline

“…Geckos do not change the timing of limb movements on uphill surfaces compared to level (Table 1 ). This is drastically different to previous studies of inclined locomotion where significant increases in stride time [ 24 , 57 ] and duty factor [ 13 , 23 , 24 ] are evident. Duty factor often increases on uphill surfaces, allowing greater time in contact with the ground to provide the extra work required to move against gravity.…”

“…Remarkably swing time did decrease on the 45° decline condition from level in our study (Table 1 ). Reduction in swing time compared to level terrain has previously been noted in birds on inclines [ 23 , 68 ]. Shortening the swing time, whilst keeping stance time constant, could be a strategy to maintain relatively consistent peak forces, as well as provide enough time for producing an impulse that can generate work for going uphill, or absorb energy (negative work) when moving downhill.…”

The metabolic cost of incline locomotion in the Svalbard rock ptarmigan (Lagopus muta hyperborea): the effects of incline grade and seasonal fluctuations in body mass

“…This method, however, relies on a difference between the regression slopes. In the present study, in common with findings in mice, crabs, quail and more recently geese, the MCoT did not differ upon incline locomotion in either season (Nudds and Codd, 2012;Taylor et al, 1972;Tullis and Andrus, 2011;Warncke et al, 1988). Applying the traditional approach to such data would therefore reveal no additional cost of lifting despite absolute energy expenditure values clearly being higher during incline locomotion.…”

“…Similar findings have been demonstrated in humans, although the curvilinear nature of metabolic cost during walking makes comparison with avian data problematic (Margaria et al, 1963). In the only avian studies to use solely walking gaits, quail on inclines of 4, 8 and 12deg shared a common slope and geese on inclines of 7deg showed no difference in MCoT compared with that on level ground (Nudds and Codd, 2012;Warncke et al, 1988). The results of both studies are in agreement with our findings, highlighting the importance of gait when measuring the energetic cost of locomotion.…”

The metabolic cost of walking on an incline in the Peacock (Pavo cristatus)

“…In a number of investigations, few kinematic parameter changes are found between horizontal and incline locomotion ( Eaton et al, 1995 ; Full & Tullis, 1990 ; Lees et al, 2013 ). In the present study, however, peacocks maintained higher DF’s on an incline than on the level ( Nudds & Codd, 2012 ). The increase in DF, and the decrease in 1/ t stance found when comparing level and incline movement ( Oldruitenborgh-Oosterbaan, Barneveld & Schamhardt, 1997 ), indicated that the increased cost of incline locomotion in the peacock was not influenced by a higher rate of muscle force development ( Kram & Taylor, 1990 ; Roberts et al, 1998 ).…”