have found the mass-specific metabolic cost of treadmill running to correlate positively and significantly with heel length. Scholz et al 4 suggested a theoretical model that explained how short heels might improve running economy (reduce metabolic cost). Producing the same plantar flexor moment
Herman van Werkhoven and Stephen J. Piazza
Kirstin S. Morris, Mark A. Osborne, Megan E. Shephard, David G. Jenkins and Tina L. Skinner
The contributions of the limbs to velocity and metabolic parameters in front-crawl swimming at different intensities have not been identified considering both stroke and kick rate. Consequently, velocity, oxygen uptake (V̇O2), and metabolic cost of swimming with the whole body (swim), the upper limbs only (pull), and lower limbs only (kick) were compared with stroke and kick rate controlled.
Twenty elite swimmers completed six 200-m trials: 2 swim, 2 pull, and 2 kick. Swim trials were guided by underwater lights at paces equivalent to 65% ± 3% and 78% ± 3% of participants’ 200-m-freestyle personal-best pace; paces were described as low and moderate, respectively. In the pull and kick trials, swimmers aimed to match the stroke and kick rates, respectively, recorded during the swim trials. V̇O2 was measured continuously, with velocity and metabolic cost calculated for each 200-m effort.
The velocity contribution of the upper limbs (mean ± SD; low 63.9% ± 6.2%, moderate 59.6% ± 4.2%) was greater than that of the lower limbs to a large extent at both intensities (low ES = 4.40, moderate ES = 4.60). The V̇O2 used by the upper limbs differed between the intensities (low 55.5% ± 6.9%, moderate 51.4% ± 4.0%; ES = 0.74). The lower limbs were responsible for a greater percentage of the metabolic cost than the upper limbs at both intensities (low 56.1% ± 9.5%, ES = 1.30; moderate 55.1% ± 6.6%, ES = 1.55).
Implementation of this testing protocol before and after a pull- or kick-training block will enable sport scientists to determine how the velocity contributions and/or metabolic cost of the upper- and lower-limb actions have responded to the training program.
Christopher A. Zirker, Bradford C. Bennett and Mark F. Abel
We examined how the application of a forward horizontal force applied at the waist alters the metabolic cost, kinematics, and external work of gait. Horizontal assist forces of 4%, 8% and 12% of a subject’s body weight were applied via our testing apparatus while subjects walked at comfortable walking speed on a level treadmill. Kinematic and metabolic parameters were measured using motion capture and ergospirometry respectively on a group of 10 healthy male subjects. Changes in kinematic and metabolic parameters were quantified and found similar to walking downhill at varying grades. A horizontal assist force of 8% resulted in the greatest reduction of metabolic cost. Changes in recovery factor, external work, and center of mass (COM) movement did not correlate with changes in metabolic rate and therefore were not driving the observed reductions in cost. The assist force may have performed external work by providing propulsion as well as raising the COM as it pivots over the stance leg. Assist forces may decrease metabolic cost by reducing the concentric work required for propulsion while increasing the eccentric work of braking. These findings on the effects of assist forces suggest novel mobility aids for individuals with gait disorders and training strategies for athletes.
Stephanie Chester, Audrey Zucker-Levin, Daniel A. Melcher, Shelby A. Peel, Richard J. Bloomer and Max R. Paquette
The purpose of this study was to compare knee and hip joint kinematics previously associated with anterior knee pain and metabolic cost among conditions including treadmill running (TR), standard elliptical (SE), and lateral elliptical (LE) in healthy runners. Joint kinematics and metabolic parameters of 16 runners were collected during all 3 modalities using motion capture and a metabolic system, respectively. Sagittal knee range of motion (ROM) was greater in LE (P < .001) and SE (P < .001) compared with TR. Frontal and transverse plane hip ROM were greater in LE compared with SE (P < .001) and TR (P < .001). Contralateral pelvic drop ROM was smaller in SE compared with TR (P = .002) and LE (P = .005). Similar oxygen consumption was found during LE and TR (P = .39), but LE (P < .001) and TR (P < .001) required greater oxygen consumption than SE. Although LE yields similar metabolic cost to TR and produces hip kinematics that may help strengthen hip abductors, greater knee flexion and abduction during LE may increase symptoms in runners with anterior knee pain. The findings suggest that research on the implications of elliptical exercise for injured runners is needed.
Jennifer L. Huberty, Jeni L. Matthews, Meynard Toledo, Lindsay Smith, Catherine L. Jarrett, Benjamin Duncan and Matthew P. Buman
important for the measurement of EE that is similar to what could be expected from a Vinyasa Flow class outside a laboratory setting. Therefore, the purpose of this study was to describe the metabolic cost (i.e., energy expenditure) of a 30-minute Ashtanga-based Vinyasa Flow yoga class using indirect
Franziska Onasch, Anthony Killick and Walter Herzog
. Rather, skiers might prefer to use a pole length that minimizes the metabolic cost of skiing at a given speed over a prolonged period of time, particularly with the ever increasing use of exclusive double poling in marathon racing over distances of 40 km and up. Based on this consideration, we propose
Ronald Howard Cox, Jared Guth, Leah Siekemeyer, Brianna Kellems, Susan Baker Brehm and Christina M. Ohlinger
The effect of active workstation implementation on speech quality in a typical work setting remains unclear.
To assess differences between sitting, standing, and walking on energy expenditure and speech quality.
Twenty-two females and 9 males read silently, read aloud, and spoke spontaneously during 3 postural conditions: sitting, standing, and walking at 1.61 km/h. Oxygen consumption (VO2), blood pressure, and rating of perceived exertion (RPE) were obtained during each condition. Expert listeners, blinded to the purpose of the study and the protocol, assessed randomized samples of the participants’ speech during reading and spontaneous speech tasks in 3 postural conditions.
Standing elevated metabolic rate significantly over sitting (3.3 ± 0.7 vs. 3.6 ± 0.9 ml·kg−1·min−1). Walking at 1.6 km/h while performing the respective tasks resulted in VO2 values of 7.0 to 8.1 ml·kg−1·min−1. There was no significant difference in the average number of syllables included in each speech sample across the conditions. The occurrence of ungrammatical pauses was minimal and did not differ across the conditions.
The significant elevation of metabolic rate in the absence of any deterioration in speech quality or RPE support the utility of using active work stations to increase physical activity (PA) in the work environment.
Gabriela Fischer, Pedro Figueiredo and Luca P. Ardigò
To investigate physiological performance determinants of the partial laps and an overall 22-km handbiking (HB) time trial in athletes with high paraplegia.
Seven male HB athletes with spinal cord injury (lesion levels thoracic 2-8) performed a laboratory maximal incremental test under cardiorespiratory-mechanical monitoring including respiratory-exchange ratio (RER), oxygen uptake (V̇O2), and mechanical power output (PO). Individual first and second ventilatory thresholds (V̇O2VT1 and V̇O2VT2), V̇O2peak, and POpeak were posteriorly identified. Athletes also performed a simulated HB time trial along a 4-lap bike circuit under cardiorespiratory measurement. Overall metabolic cost (C) and %V̇O2peak (ratio of V̇O2 to V̇O2peak) were calculated from race data. Race performance was defined as mean race velocity (v).
athletes completed the 22-km HB time trial in 45 ± 6 min, at 29.9 ± 3.6 km/h, with %V̇O2peak = 0.86 ± 0.10 and RER = 1.07 ± 0.17. V̇O2peak (r = .89, P = .01), POpeak (r = .85, P = .02), V̇O2VT1 (r = .96, P = .001), V̇O2VT2 (r = .92, P = .003), and C (2nd lap, r = .78; 3rd lap, r = .80; and 4th lap, r = .80) were significantly (P < .05) positively correlated with race performance. Within-subjects correlation coefficient revealed a large and significant (r = .68, P < .001) relationship between %V̇O2peak and v.
V̇O2peak, POpeak, ventilatory thresholds, %V̇O2peak, and C appeared to be important physiological performance determinants of HB time trial.
Mhairi K. MacLean and Daniel P. Ferris
successful in these environments, robotic devices must be suited to the task specificity of the demands. Many robotic exoskeletons that have been described or studied in the scientific literature have been evaluated based on their ability to reduce the metabolic cost of walking and/or running, because
Marco Arkesteijn, Simon Jobson, James Hopker and Louis Passfield
Previous research has shown that cycling in a standing position reduces cycling economy compared with seated cycling. It is unknown whether the cycling intensity moderates the reduction in cycling economy while standing.
The aim was to determine whether the negative effect of standing on cycling economy would be decreased at a higher intensity.
Ten cyclists cycled in 8 different conditions. Each condition was either at an intensity of 50% or 70% of maximal aerobic power at a gradient of 4% or 8% and in the seated or standing cycling position. Cycling economy and muscle activation level of 8 leg muscles were recorded.
There was an interaction between cycling intensity and position for cycling economy (P = .03), the overall activation of the leg muscles (P = .02), and the activation of the lower leg muscles (P = .05). The interaction showed decreased cycling economy when standing compared with seated cycling, but the difference was reduced at higher intensity. The overall activation of the leg muscles and the lower leg muscles, respectively, increased and decreased, but the differences between standing and seated cycling were reduced at higher intensity.
Cycling economy was lower during standing cycling than seated cycling, but the difference in economy diminishes when cycling intensity increases. Activation of the lower leg muscles did not explain the lower cycling economy while standing. The increased overall activation, therefore, suggests that increased activation of the upper leg muscles explains part of the lower cycling economy while standing.