IJSM/5215/28.12.2015/MPS
Clinical Sciences
Metabolic Differences Between Shod and Barefoot Walking in Children
Authors
S. P.Shultz1, S. D. Houltham1, S. M. Kung1, P. Hume2, P. W. Fink3
Affiliations
1
Key Words ▶ physiology ● ▶ paediatrics ● ▶ footwear ● ▶ gait ●
Abstract
School of Sport and Exercise, Massey University, Wellington, New Zealand Institute of Sport and Recreation Research New Zealand, AUT University, Auckland, New Zealand 3 School of Sport & Exercise, Massey University, Palmerston North, New Zealand
▼
Footwear affects the biomechanics of children’s gait; however, there has been less research addressing the energetics of walking with and without shoes. This study investigated the effects of barefoot and shod walking on metabolic parameters in children. 25 children (9.7 ± 1.4 years) walked at a self-selected pace for 5 min on an instrumented treadmill under 2 footwear conditions (barefoot, running shoe). Vertical oscillations of centre of mass were calculated from ground reaction forces. Expired gases were collected in the last minute of each trial. Paired t-tests revealed significantly higher oxygen con-
Introduction
▼
accepted after revision November 23, 2015 Bibliography DOI http://dx.doi.org/ 10.1055/s-0035-1569349 Published online: 2016 Int J Sports Med 2016 © Georg Thieme Verlag KG Stuttgart · New York ISSN 0172-4622 Correspondence Dr. Sarah Shultz School of Sport and Exercise Massey University PO Box 756, Wellington, New Zealand, 6140 Tel.: + 64/497/93 496 Fax: + 64/480/14 994 [email protected]
The use of footwear in the modern urban environment is common and can begin as early as the first developmental stages of walking. Cushioned running shoes have an elevated heel, arch support and a stiff midsole, all of which can affect the biomechanics of children’s gait. The additional mass and length that a shoe adds to the lower limb can influence spatiotemporal parameters, specifically increasing stride length and velocity [16, 20]. Increased double-limb support time and a wider base of support have been the suggested consequences of diminished proprioceptive feedback when wearing shoes [24]. Additionally, shoes affect joint kinematics by decreasing intrinsic foot motion [29, 30] and subsequently increasing hip flexion [15]. The restriction to foot motion can have a negative effect on the lengthening of medial longitudinal and transverse arches, potentially diminishing their capacity to store elastic energy [30]. If footwear can directly influence a child’s gait, then it could be suggested that metabolic cost would also be impacted when walking shod.
sumption (17.6 ± 2.5 ml.kg − 1.min − 1 vs. 16.3 ± 3.1 ml.kg − 1.min − 1), energy expenditure (3.25 ± 0.86 kcal.min − 1 vs. 2.97 ± 0.68 kcal.min − 1), and economy (298.2 ± 47.5 ml.kg − 1.km − 1 vs. 275.9 ± 56.9 ml.kg − 1.km − 1) during the shod condition. There was no difference in substrate utilization between conditions. The barefoot condition elicited a smaller centre of mass vertical displacement (1.24 ± 0.14 cm vs. 1.34 ± 0.17 cm). At a natural walking speed, barefoot walking is more economical than shod walking at the same velocity in children. The higher energy cost of shod walking should be considered when evaluating the use of footwear by children.
Research in adults has shown that footwear use is associated with higher energy cost of walking [5, 14, 27] and running [11]. It is believed that changes to tissue stiffness, specifically the longitudinal arch and Achilles tendon, can impact elastic energy storage and subsequently diminish gait economy when shod [22]. In contrast to adults, little, if any data are available showing the effect of shod compared to barefoot walking on metabolic parameters in children. Such data may add support to research which shows changes to joint kinematics and as well as evidence of developmental deformities in habitually shod children. As walking is commonly performed activity, any change to energy cost can have substantial effects on overall metabolism. Therefore the purpose of this study was to examine the effects of barefoot and shod walking on metabolic parameters in children. Metabolic parameters included oxygen consumption, energy expenditure, substrate utilization, and economy.
Shultz S et al. Metabolic differences between shod … Int J Sports Med
Downloaded by: Weizmann Institute of Science. Copyrighted material.
2
IJSM/5215/28.12.2015/MPS
Clinical Sciences
▼
Participants
25 children (11 males, 14 females; age: 9.7 ± 1.4 years; mass: 39.4 ± 11.9 kg; height: 1.44 ± 0.10 m) participated in the study. An age range of 8–12 years was chosen to ensure established gait patterns [4, 7] and homogenous neuromuscular maturity [9] across the cohort. Participants were screened for neuromusculoskeletal disease and previous history of lower extremity injuries or surgeries within 6 months prior to the study. All participants fasted for a minimum of 4 h prior to the testing session. Participants and their parents provided informed written assent and consent, respectively. The study was approved by the University Human Ethics Committee (Southern A Application 12/27) and conducted according to ethical standards [12].
Protocol
Participants completed 2 walking trials on a Bertec instrumented treadmill (Bertec, Corp; Columbus, OH) at a self-selected speed (1.00 ± 0.13 m/s). To determine self-selected speed, 2 pairs of timing gates were configured as a 1 m × 6 m walkway. Participants were positioned 1 m behind the first pair of timing gates, and instructed to walk normally through the gates without slowing down. An average of 5 over-ground trials was calculated as the self-selected speed [2]. A same-day familiarization session was utilized and walking speed was adjusted if the participant struggled to maintain speed while on the treadmill [15]. Participants then completed 5-min trials under 2 conditions (shod, barefoot), in a randomized order and with a 5-min rest period between trials. Force plate data were sampled in 20 s intervals at 120 s, 180 s and 240 s time points of each walking trial; the data collected at the 240 s time point was used to calculate vertical centre of mass displacement (vCoM). Breath-by-breath indirect calorimetry data were collected during each 5-min trial using a Cosmed K4 b2 portable gas analyser (Rome, Italy); data averaged during the last minute of the trial were used to calculate energetics. A standardized shoe (248 ± 28 g) was used for the shod condition (model KJ553TLY, New Balance, Boston, MA).
Energetic measurements
Expired gases were collected using a mask fitted securely over the face, covering the mouth and nose, as this is better tolerated by children than a nose clip and mouth piece [18]. Energy expenditure was calculated by using the respiratory exchange ratio (RER) to determine the energy equivalent of oxygen (kcal.LO2 − 1), which was multiplied by the oxygen consumption rate (L.min − 1). Percentage substrate utilization was calculated using the following formulas: %fat = (1.0 – RER)/RER range × 100; %CHO = 100- %fat.
Variable VO2 (ml.kg − 1.min − 1) Energy Expenditure (kcal.min − 1) CHO (g.min − 1) Fat (g.min − 1) Economy (ml.kg − 1.km − 1) Centre of mass vertical displacement (cm)
The percentages were then applied to the energy expenditure to determine fat and carbohydrate oxidation. Economy (ml.kg − 1. km − 1) was calculated as the normalization of oxygen consumption rate to body mass and walking speed.
Vertical centre of mass displacement
To determine vCoM, acceleration of the centre of mass a(t) was calculated by subtracting the weight (N) of the participant from the summed left and right foot ground reaction forces (N), and then dividing that value by the participant’s mass (kg). Data were divided into strides by finding the right foot strike for each stride, determined as the first time point in each stride where the right vertical force exceeded 25 N. The vertical oscillation (cm) was then calculated for each stride between right foot strikes. The acceleration was integrated twice to get the vertical position y(t). This yields the equation t
y t a t dt 2 ct , 0
where a(t) is the acceleration signal, with the time set to zero at each right foot strike. To correct for drift in integration, and to account for the unknown initial velocity, it was assumed that the vertical height at each right foot strike was identical, and arbitrarily set to zero. This implies that y(0) = y(T) = 0 where T is the time between right foot strikes. Solving the equation for position to find c yields t
y t a t dt 2
T
0
0
a t dt 2 T
For the calculation of integrals, Simpson’s rule was used and vertical oscillation was defined as the range (maximum-minimum) for y(t) during each gait cycle.
Statistical analyses
Paired t-tests were used to analyse differences between barefoot and shod walking conditions for metabolic parameters (oxygen consumption, energy expenditure, substrate utilization, and economy) and vCoM (SPSS Statistics v 20; IBM Corp, Armonk, NY). Significance was set at p
Clinical Sciences
Metabolic Differences Between Shod and Barefoot Walking in Children
Authors
S. P.Shultz1, S. D. Houltham1, S. M. Kung1, P. Hume2, P. W. Fink3
Affiliations
1
Key Words ▶ physiology ● ▶ paediatrics ● ▶ footwear ● ▶ gait ●
Abstract
School of Sport and Exercise, Massey University, Wellington, New Zealand Institute of Sport and Recreation Research New Zealand, AUT University, Auckland, New Zealand 3 School of Sport & Exercise, Massey University, Palmerston North, New Zealand
▼
Footwear affects the biomechanics of children’s gait; however, there has been less research addressing the energetics of walking with and without shoes. This study investigated the effects of barefoot and shod walking on metabolic parameters in children. 25 children (9.7 ± 1.4 years) walked at a self-selected pace for 5 min on an instrumented treadmill under 2 footwear conditions (barefoot, running shoe). Vertical oscillations of centre of mass were calculated from ground reaction forces. Expired gases were collected in the last minute of each trial. Paired t-tests revealed significantly higher oxygen con-
Introduction
▼
accepted after revision November 23, 2015 Bibliography DOI http://dx.doi.org/ 10.1055/s-0035-1569349 Published online: 2016 Int J Sports Med 2016 © Georg Thieme Verlag KG Stuttgart · New York ISSN 0172-4622 Correspondence Dr. Sarah Shultz School of Sport and Exercise Massey University PO Box 756, Wellington, New Zealand, 6140 Tel.: + 64/497/93 496 Fax: + 64/480/14 994 [email protected]
The use of footwear in the modern urban environment is common and can begin as early as the first developmental stages of walking. Cushioned running shoes have an elevated heel, arch support and a stiff midsole, all of which can affect the biomechanics of children’s gait. The additional mass and length that a shoe adds to the lower limb can influence spatiotemporal parameters, specifically increasing stride length and velocity [16, 20]. Increased double-limb support time and a wider base of support have been the suggested consequences of diminished proprioceptive feedback when wearing shoes [24]. Additionally, shoes affect joint kinematics by decreasing intrinsic foot motion [29, 30] and subsequently increasing hip flexion [15]. The restriction to foot motion can have a negative effect on the lengthening of medial longitudinal and transverse arches, potentially diminishing their capacity to store elastic energy [30]. If footwear can directly influence a child’s gait, then it could be suggested that metabolic cost would also be impacted when walking shod.
sumption (17.6 ± 2.5 ml.kg − 1.min − 1 vs. 16.3 ± 3.1 ml.kg − 1.min − 1), energy expenditure (3.25 ± 0.86 kcal.min − 1 vs. 2.97 ± 0.68 kcal.min − 1), and economy (298.2 ± 47.5 ml.kg − 1.km − 1 vs. 275.9 ± 56.9 ml.kg − 1.km − 1) during the shod condition. There was no difference in substrate utilization between conditions. The barefoot condition elicited a smaller centre of mass vertical displacement (1.24 ± 0.14 cm vs. 1.34 ± 0.17 cm). At a natural walking speed, barefoot walking is more economical than shod walking at the same velocity in children. The higher energy cost of shod walking should be considered when evaluating the use of footwear by children.
Research in adults has shown that footwear use is associated with higher energy cost of walking [5, 14, 27] and running [11]. It is believed that changes to tissue stiffness, specifically the longitudinal arch and Achilles tendon, can impact elastic energy storage and subsequently diminish gait economy when shod [22]. In contrast to adults, little, if any data are available showing the effect of shod compared to barefoot walking on metabolic parameters in children. Such data may add support to research which shows changes to joint kinematics and as well as evidence of developmental deformities in habitually shod children. As walking is commonly performed activity, any change to energy cost can have substantial effects on overall metabolism. Therefore the purpose of this study was to examine the effects of barefoot and shod walking on metabolic parameters in children. Metabolic parameters included oxygen consumption, energy expenditure, substrate utilization, and economy.
Shultz S et al. Metabolic differences between shod … Int J Sports Med
Downloaded by: Weizmann Institute of Science. Copyrighted material.
2
IJSM/5215/28.12.2015/MPS
Clinical Sciences
▼
Participants
25 children (11 males, 14 females; age: 9.7 ± 1.4 years; mass: 39.4 ± 11.9 kg; height: 1.44 ± 0.10 m) participated in the study. An age range of 8–12 years was chosen to ensure established gait patterns [4, 7] and homogenous neuromuscular maturity [9] across the cohort. Participants were screened for neuromusculoskeletal disease and previous history of lower extremity injuries or surgeries within 6 months prior to the study. All participants fasted for a minimum of 4 h prior to the testing session. Participants and their parents provided informed written assent and consent, respectively. The study was approved by the University Human Ethics Committee (Southern A Application 12/27) and conducted according to ethical standards [12].
Protocol
Participants completed 2 walking trials on a Bertec instrumented treadmill (Bertec, Corp; Columbus, OH) at a self-selected speed (1.00 ± 0.13 m/s). To determine self-selected speed, 2 pairs of timing gates were configured as a 1 m × 6 m walkway. Participants were positioned 1 m behind the first pair of timing gates, and instructed to walk normally through the gates without slowing down. An average of 5 over-ground trials was calculated as the self-selected speed [2]. A same-day familiarization session was utilized and walking speed was adjusted if the participant struggled to maintain speed while on the treadmill [15]. Participants then completed 5-min trials under 2 conditions (shod, barefoot), in a randomized order and with a 5-min rest period between trials. Force plate data were sampled in 20 s intervals at 120 s, 180 s and 240 s time points of each walking trial; the data collected at the 240 s time point was used to calculate vertical centre of mass displacement (vCoM). Breath-by-breath indirect calorimetry data were collected during each 5-min trial using a Cosmed K4 b2 portable gas analyser (Rome, Italy); data averaged during the last minute of the trial were used to calculate energetics. A standardized shoe (248 ± 28 g) was used for the shod condition (model KJ553TLY, New Balance, Boston, MA).
Energetic measurements
Expired gases were collected using a mask fitted securely over the face, covering the mouth and nose, as this is better tolerated by children than a nose clip and mouth piece [18]. Energy expenditure was calculated by using the respiratory exchange ratio (RER) to determine the energy equivalent of oxygen (kcal.LO2 − 1), which was multiplied by the oxygen consumption rate (L.min − 1). Percentage substrate utilization was calculated using the following formulas: %fat = (1.0 – RER)/RER range × 100; %CHO = 100- %fat.
Variable VO2 (ml.kg − 1.min − 1) Energy Expenditure (kcal.min − 1) CHO (g.min − 1) Fat (g.min − 1) Economy (ml.kg − 1.km − 1) Centre of mass vertical displacement (cm)
The percentages were then applied to the energy expenditure to determine fat and carbohydrate oxidation. Economy (ml.kg − 1. km − 1) was calculated as the normalization of oxygen consumption rate to body mass and walking speed.
Vertical centre of mass displacement
To determine vCoM, acceleration of the centre of mass a(t) was calculated by subtracting the weight (N) of the participant from the summed left and right foot ground reaction forces (N), and then dividing that value by the participant’s mass (kg). Data were divided into strides by finding the right foot strike for each stride, determined as the first time point in each stride where the right vertical force exceeded 25 N. The vertical oscillation (cm) was then calculated for each stride between right foot strikes. The acceleration was integrated twice to get the vertical position y(t). This yields the equation t
y t a t dt 2 ct , 0
where a(t) is the acceleration signal, with the time set to zero at each right foot strike. To correct for drift in integration, and to account for the unknown initial velocity, it was assumed that the vertical height at each right foot strike was identical, and arbitrarily set to zero. This implies that y(0) = y(T) = 0 where T is the time between right foot strikes. Solving the equation for position to find c yields t
y t a t dt 2
T
0
0
a t dt 2 T
For the calculation of integrals, Simpson’s rule was used and vertical oscillation was defined as the range (maximum-minimum) for y(t) during each gait cycle.
Statistical analyses
Paired t-tests were used to analyse differences between barefoot and shod walking conditions for metabolic parameters (oxygen consumption, energy expenditure, substrate utilization, and economy) and vCoM (SPSS Statistics v 20; IBM Corp, Armonk, NY). Significance was set at p
