Skiing economy and kinematic during a field double poling roller skiing among novice and experienced cross-country skiers

To assess the skiing economy (SE) and kinematics during double poling (DP) roller skiing between two groups of skiers in a field setting. Five experienced and five novice male skiers performed a SEDP test at 16 km∙h-1 on an outdoor athletics track. Gas exchange parameters were measured to determine SEDP. A two-dimensional video was filmed to measure the kinematics variables. Experienced skiers exhibited a 21% lower oxygen cost than novice skiers (p = 0.016) in DP, indicating a strong association between SEDP, cycle length and cycle rate (p < 0.001). Additionally, before the poling phase, experienced skiers manifested significantly greater maximum hip and knee extension angles than novice skiers (p < 0.001). During the poling phase, experienced skiers with a greater pole plant angle (p = 0.001), longer flexion time (p < 0.001) and higher flexion angular velocity in the elbow joint (p < 0.05) demonstrated better SEDP. There was an interaction effect of the one-repetition maximum bench press × group in SEDP (b = - 0.656, SE = 0.097, t = - 6.78, p = 0.001). Therefore, experienced skiers with better SEDP demonstrated more efficient cycles, potentially accomplished using dynamic full-body DP motion to ascertain effective propulsion. Combined upper body strength and ski-specific skill training may enhance SEDP in novice skiers.

Prediction of Maximum Lactate Concentration During an All-Out Anaerobic Test in Elite Ice Hockey Players

The lack of specific on-ice tests to predict maximum lactate concentration limits the ability of coaches to better track and develop their ice hockey players. Thus, this study aimed to develop an equation for indirectly assessing the maximum lactate concentration produced from an all-out on-ice skating effort in elite adolescent ice hockey players. Twenty elite male ice hockey players participated in this study (age = 15.7 ± 1.0 year). The lactate anaerobic skating test (LAST) consisted of skating back and forth on an 18.2 m course at maximal speed with abrupt stops at each end for a total of 6 shuttles (total distance = 218.2 m; average time = 52.0 ± 2.0 s). The oxygen uptake was measured using a portable metabolic analyzer (Cosmed K4b2) and the maximum post-exercise lactate concentration with a Lactate Pro analyzer. The variables used to estimate lactate concentration were time, heart rate, number of skating strides in the last shuffle (6th) and the skating stride index. The average maximum lactate concentration was 14.4 mmol· L-1, which is expected in elite players. The analysis of explained common variance using T-test (r2 = 0.759) and linear regression (r2 = 0.863) demonstrates the validity of the model. Additionally, the root mean square error (RMSE = 0.60 mmol· L-1), the mean absolute error (MAE = 0.45mmol· L-1) and the standard error of estimate (SEE = 0.69 mmol· L-1) values further confirm the accuracy of the model. Thus, using simple and easy-to-measure variables (i.e., time and skating stride), coaches will be able to monitor more effectively their players' progress in an effort to optimize their individual on-ice performance.

Cardiac output and arteriovenous oxygen difference contribute to lower peak oxygen uptake in patients with fibromyalgia

BACKGROUND

Patients with fibromyalgia (FM) exhibit low peak oxygen uptake ([Formula: see text]O_2peak). We aimed to detect the contribution of cardiac output to ([Formula: see text]) and arteriovenous oxygen difference [Formula: see text] to [Formula: see text] from rest to peak exercise in patients with FM.

METHODS

Thirty-five women with FM, aged 23 to 65 years, and 23 healthy controls performed a step incremental cycle ergometer test until volitional fatigue. Alveolar gas exchange and pulmonary ventilation were measured breath-by-breath and adjusted for fat-free body mass (FFM) where appropriate. [Formula: see text] (impedance cardiography) was monitored. [Formula: see text] was calculated using Fick's equation. Linear regression slopes for oxygen cost (∆[Formula: see text]O₂/∆work rate) and [Formula: see text] to [Formula: see text]O₂ (∆[Formula: see text]/∆[Formula: see text]O₂) were calculated. Normally distributed data were reported as mean ± SD and non-normal data as median [interquartile range].

RESULTS

[Formula: see text]O_2peak was lower in FM patients than in controls (22.2 ± 5.1 vs. 31.1 ± 7.9 mL∙min^-1∙kg^-1, P < 0.001; 35.7 ± 7.1 vs. 44.0 ± 8.6 mL∙min^-1∙kg FFM^-1, P < 0.001). [Formula: see text] and C(a-v)O₂ were similar between groups at submaximal work rates, but peak [Formula: see text] (14.17 [13.34-16.03] vs. 16.06 [15.24-16.99] L∙min^-1, P = 0.005) and C(a-v)O₂ (11.6 ± 2.7 vs. 13.3 ± 3.1 mL O₂∙100 mL blood^-1, P = 0.031) were lower in the FM group. No significant group differences emerged in ∆[Formula: see text]O₂/∆work rate (11.1 vs. 10.8 mL∙min^-1∙W^-1, P = 0.248) or ∆[Formula: see text]/∆[Formula: see text]O₂ (6.58 vs. 5.75, P = 0.122) slopes.

CONCLUSIONS

Both [Formula: see text] and C(a-v)O₂ contribute to lower [Formula: see text]O_2peak in FM. The exercise responses were normal and not suggestive of a muscle metabolism pathology.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT03300635. Registered 3 October 2017-Retrospectively registered. https://clinicaltrials.gov/ct2/show/NCT03300635 .

Peak performance and cardiometabolic responses of modern US army soldiers during heavy, fatiguing vest-borne load carriage

INTRODUCTION

Physiological limits imposed by vest-borne loads must be defined for optimal performance monitoring of the modern dismounted warfighter.

PURPOSE

To evaluate how weighted vests affect locomotion economy and relative cardiometabolic strain during military load carriage while identifying key physiological predictors of exhaustion limits.

METHODS

Fifteen US Army soldiers (4 women, 11 men; age, 26 ± 8 years; height, 173 ± 10 cm; body mass (BM), 79 ± 16 kg) performed four incremental walking tests with different vest loads (0, 22, 44, or 66% BM). We examined the effects of vest-borne loading on peak walking speed, the physiological costs of transport, and relative work intensity. We then sought to determine which of the cardiometabolic indicators (oxygen uptake, heart rate, respiration rate) was most predictive of task failure.

RESULTS

Peak walking speed significantly decreased with successively heavier vest loads (p < 0.01). Physiological costs per kilometer walked were significantly higher with added vest loads for each measure (p < 0.05). Relative oxygen uptake and heart rate were significantly higher during the loaded trials than the 0% BM trial (p < 0.01) yet not different from one another (p > 0.07). Conversely, respiration rate was significantly higher with the heavier load in every comparison (p < 0.01). Probability modeling revealed heart rate as the best predictor of task failure (marginal R², 0.587, conditional R², 0.791).

CONCLUSION

Heavy vest-borne loads cause exceptional losses in performance capabilities and increased physiological strain during walking. Heart rate provides a useful non-invasive indicator of relative intensity and task failure during military load carriage.

The impact of the energy cost of walking on the quality of life of post-stroke individuals: A one-year longitudinal study

BACKGROUND

The increased energy cost of walking (Cw) for stroke patients affects the walking function and walking independence of stroke patients. However, its impact on quality of life (QoL) has never been studied.

OBJECTIVE

Assess the association between Cw and QoL for post-stroke individuals in the year following hospital discharge.

METHOD

Thirty-seven individuals with stroke were included. QoL was assessed by the EuroQol-5 Dimensions on the day after hospital discharge (T0), at six months (T1) and at one year after hospital discharge (T2). Concomitant an evaluation of Cw, mood disorders (HADS), fatigue, independence in activities of daily living and the presence of a family caregiver was performed. The association between QoL and the different covariates was analyzed using multiple regression analysis.

RESULTS

At T2, data from 29 individuals were analyzable. Multiple regression analyses showed Cw had a significant influence on the QoL at T1 (coeff -0.42 (-0.71 to -0.12), P = .008) and T2 (coeff -0.49 (-0.71 to -0.26), P < .001). HADS score was the only other variable to significantly impact variances of QoL at T0, T1 and T2. Moreover, we showed that Cw at T0 explained 29% of variances of QoL at T1 and 42% at T2.

CONCLUSION

Cw appears to be an independent factor in the QoL of individuals with stroke at six months and one year after hospital discharge. In addition, the initial Cw and HADS are predictive of QoL at one year highlighting the importance of early interventions in these two dimensions to improve QoL over the long term.

Oxygen Cost of Walking in People With Multiple Sclerosis and Its Association With Fatigue: A Systematic Review and Meta-analysis

BACKGROUND

This systematic review and meta-analysis aimed to compare the oxygen cost of walking in individuals with multiple sclerosis (MS) and controls and to assess the relationship between oxygen cost of walking and fatigue in individuals with MS.

METHODS

Four databases (CINAHL, MEDLINE, ProQuest, Web of Science) were searched up to September 2020. Studies were included if they recruited adults with MS and either compared oxygen cost of walking in those with MS and a control population or determined the relationship between oxygen cost of walking and fatigue. Meta-analysis of the standardized mean difference in oxygen cost of walking between individuals with MS and controls was performed.

RESULTS

Nine studies were included in this review, of which 7 compared oxygen cost of walking in individuals with MS (n = 176) and controls (n = 142) and 4 investigated the relationship between oxygen cost of walking and fatigue. Meta-analysis revealed that individuals with MS (with predominantly mild-to-moderate disability) had a significantly higher oxygen cost of walking compared with controls (standardized mean difference = 2.21, 95% CI = 0.88 to 3.54, P = .001). In addition, 3 studies found a significant yet weak positive association between oxygen cost of walking and fatigue.

CONCLUSIONS

Individuals with MS expend more energy when walking compared with controls. This increase in energy expenditure may contribute to the development of fatigue, as some studies found that higher oxygen costs of walking were associated with greater fatigue. Future studies should investigate whether reducing energy expenditure during movement improves fatigue.

Impact of step length asymmetry on walking energetics in women with hip Osteoarthritis: A pilot study

A step length difference between the involved and uninvolved limbs in participants with hip osteoarthritis (OA) has been reported. The implications of step length asymmetry on other aspects of walking mechanics are as yet unknown. The objective of the current study was to evaluate the consequences of step length asymmetry on motion of the center of mass (COM) and energy cost of walking. We hypothesized that (i) increased step length asymmetry is associated with decreased mechanical energy exchange; (ii) decreased mechanical energy exchange is associated with increased O₂ cost; (iii) increased step length asymmetry is associated with increased oxygen O₂ cost during walking in women with hip OA. We evaluated 24 women with unilateral hip OA using motion analysis as participants walked on a treadmill at self-selected speeds. Kinematic data were collected to compute step length asymmetry and mechanical energy exchange through the motion of COM. We also used a portable metabolic system to measure the energy cost of walking simultaneously. We used Pearson correlations and linear regression to test our hypotheses. We found that more asymmetric step lengths were associated with lower mechanical energy exchange (R² = 0.231, p = 0.017). More mechanical energy exchange was associated with lower O₂ cost during gait (R² = 0.284, p = 0.009). Mechanical energy exchange predicted 54.5% of the variance in O₂ cost after adjusting for self-selected walking speed. Findings suggest that modifying step length asymmetry could enhance metabolic gait efficiency indirectly by improving mechanical energy exchange in participants with hip OA.

Energetics of walking in individuals with cerebral palsy and typical development, across severity and age: A systematic review and meta-analysis

BACKGROUND

Individuals with cerebral palsy (CP) report physical fatigue as a main cause of limitation, deterioration and eventually cessation of their walking ability. A consequence of higher level of fatigue in individuals with CP leads to a less efficient and long-distance walking ability.

RESEARCH QUESTION

This systematic review investigates the difference in 1) walking energy expenditure between individuals with CP and age-matched typically developing (TD) individuals; and 2) energetics of walking across Gross Motor Function Classification System (GMFCS) levels and age.

METHODS

Five electronic databases (PubMed, Web of Science, CINAHL, ScienceDirect and Scopus) were searched using search terms related to CP and energetics of walking.

RESULTS

Forty-one studies met inclusion criteria. Thirty-one studies compared energy expenditure between CP and age-matched controls. Twelve studies correlated energy expenditure and oxygen cost across GMFCS levels. Three studies investigated the walking efficiency across different ages or over a time period. A significant increase of energy expenditure and oxygen cost was found in individuals with CP compared to TD age-matched individuals, with a strong relationship across GMFCS levels.

SIGNIFICANCE

Despite significant differences between individuals with CP compared to TD peers, variability in methods and testing protocols may play a confounding role. Analysis suggests oxygen cost being the preferred/unbiased physiological parameter to assess walking efficacy in CP. To date, there is a knowledge gap on age-related changes of walking efficiency across GMFCS levels and wider span of age ranges. Further systematic research looking at longitudinal age-related changes of energetics of walking in this population is warranted.

Which method should be chosen to estimate the oxygen cost of walking in post-stroke individuals?

BACKGROUND

The oxygen cost of walking (Cw) represents the energy expenditure involved in walking, which is a major concern when quantifying physical activity in stroke. Recent studies have reported that Cw may be estimated accurately with a prediction equation using the self-self-selected walking speed (S_free).

RESEARCH QUESTION

To evaluate the validity of Cw estimates according to different modalities of S_free measurements (10-m walking test, 6-minute walking test, GaitRite system).

METHODS

Twenty-one stroke individuals in subacute phase who were able to walk without human aid were included. Cw was estimated from the walking speed measured during a 10-m walking test, a 6-minute walking test and a recording on a GaitRite system. The values of the Cw estimates were compared to those measured by a respiratory gas exchange analyzer (Metamax3b).

RESULTS

The findings showed that there is no significant difference between the Cw measured by Metamax3b and the Cw estimates regardless of the modalities used to measure S_free (Fvalue = 0.02; pvalue = 0.99). The mean bias between Cw measured by the Metamax3b and those estimated using the different S_free measurement modalities was less than 2.5 % of the mean Cw value. Test retest reliability was excellent with an intraclass correlation coefficient higher than 0.95.

SIGNIFICANCE

in stroke survivors who are able to walk independently without human aid, the use of a 10-m walking test, a 6-minute walking test or a GaitRite recording can be considered validated for estimating Cw.

Effects of modern military backpack loads on walking speed and cardiometabolic responses of US Army Soldiers

INTRODUCTION

Military leaders must understand how modern military equipment loads affect trade-offs between movement speed and physiological strain to optimize pacing strategies.

PURPOSE

To evaluate the effects of load carried in a recently developed military backpack on the walking speed and cardiometabolic responses of dismounted warfighters.

METHODS

Fifteen soldiers (1 woman, 14 men; age, 22 ± 2 years; height, 173 ± 7 cm; body mass (BM), 73 ± 10 kg) completed incremental walking tests with four external load conditions (0, 22, 44, or 66% BM) using the US Army's newest backpack: the Modular Lightweight Load-Carrying Equipment 4000 (MOLLE 4000). Oxygen uptake (V̇O₂) and heart rate (HR) were evaluated relative to maximal values (V̇O_2max and HR_max respectively). Testing ceased when participants completed the highest tested speed (1.97 m s^-1), exceeded a respiratory exchange ratio (RER) of 1.00, or reached volitional exhaustion.

RESULTS

Peak speed significantly decreased (p < 0.03) with successively heavier loads (0% BM, 1.95 ± 0.06 m s^-1; 22% BM, 1.87 ± 0.10 m s^-1; 44% BM, 1.69 ± 0.13 m s^-1; 66% BM, 1.48 ± 0.13 m s^-1). Peak V̇O₂ was significantly lower (p < 0.01) with 0% BM (47 ± 5% V̇O_2max) than each load (22% BM, 58 ± 8% V̇O_2max; 44% BM, 63 ± 10% V̇O_2max; 66% BM, 61 ± 11% V̇O_2max). Peak HR was significantly lower (p < 0.01) with 0% BM (71 ± 5% HR_max) versus each load (22% BM, 83 ± 6% HR_max; 44% BM, 87 ± 6% HR_max; 66% BM, 88 ± 6% HR_max).

CONCLUSION

Overburdened warfighters suffer severe impairments in walking speed even when carrying recently developed military load carriage equipment. Our results suggest that the relative work intensity of heavy load carriage may be better described when expressed relative to HR_max versus V̇O_2max.

Performance determinants, running energetics and spatiotemporal gait parameters during a treadmill ultramarathon

Purpose

The objective of this study was to investigate the changes in metabolic variables, running energetics and spatiotemporal gait parameters during an 80.5 km treadmill ultramarathon and establish which key predictive variables best determine ultramarathon performance.

Methods

Twelve participants (9 male and 3 female, age 34 ± 7 years, and maximal oxygen uptake (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}$$\end{document}V˙O_2max) 60.4 ± 5.8 ml·kg⁻¹·min⁻¹) completed an 80.5 km time trial on a motorised treadmill in the fastest possible time. Metabolic variables: oxygen consumption (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}$$\end{document}V˙O₂), carbon dioxide production (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}$$\end{document}V˙CO₂) and pulmonary ventilation (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}$$\end{document}V˙_E) were measured via indirect calorimetry every 16.1 km at a controlled speed of 8 km·h⁻¹ and used to calculate respiratory exchange ratio (RER), the energy cost of running (Cr) and fractional utilisation of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}$$\end{document}V˙O_2max (F). Spatiotemporal gait parameters: stride length (SL) and cadence (SPM) were calculated via tri-axial accelerometery.

Results

Trial completion time was 09:00:18 ± 01:14:07 (hh:mm:ss). There were significant increases in \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}$$\end{document}V˙O₂, Cr, F, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot{V}$$\end{document}V˙_E and heart rate (HR) (p < 0.01); a significant decrease in RER (p < 0.01) and no change in SL and SPM (p > 0.05) across the measured timepoints. F and Cr accounted for 61% of the variance in elapsed finish time (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$R_{{{\text{adj}}}}^{{2}}$$\end{document}Radj2 = 0.607, p < 0.01).

Conclusion

A treadmill ultramarathon elicits significant changes in metabolic variables, running energetics and spatiotemporal gait parameters. With F and Cr explaining 61% of variance in finish time. Therefore, those able to maintain a higher F, while adopting strategies to minimise an increase in Cr may be best placed to maximise ultramarathon performance.

A comparison of economy between two different backpack designs for runners

We compared two backpack designs (back/front or back only) in twelve recreational runners (age 22.0 ± 1.7years). An initial incremental exercise test (VO₂max 52.2 ± 4.7 ml kg^-1.min^-1) was conducted, followed by four tests of 20 min duration (running speed 9.8 ± 1.1 km/h) with loads carried of 0, 1 kg, 3 kg, and 6 kg with the two backpack designs in a randomized order. Economy was assessed by energy cost of running (CR), oxygen cost (O₂ cost), heart rate (HR) and rate of perceived exertion (RPE). Repeated measure ANOVA revealed a non-significant main effect for CR, O₂ cost, HR, RPE between systems. Post-hoc comparison of significant time × position interaction showed for CR, F(3,33) = 5.34, p < .01, η_p² = 0.33, and O₂ cost, F(3,33) = 5.15, p < .01, η_p² = 0.32, that carrying weight in the back/front were significantly lower after 20 min (CR: p = .02 and O₂ cost: p = .03). These results suggest, that for longer runs the equal distribution of weight is advantageous.

Physiological and Biomechanical Responses of Highly Trained Distance Runners to Lower-Body Positive Pressure Treadmill Running

Background

As a way to train at faster running speeds, add training volume, prevent injury, or rehabilitate after an injury, lower-body positive pressure treadmills (LBPPT) have become increasingly commonplace among athletes. However, there are conflicting evidence and a paucity of data describing the physiological and biomechanical responses to LBPPT running in highly trained or elite caliber runners at the running speeds they habitually train at, which are considerably faster than those of recreational runners. Furthermore, data is lacking regarding female runners’ responses to LBPPT running. Therefore, this study was designed to evaluate the physiological and biomechanical responses to LBPPT running in highly trained male and female distance runners.

Methods

Fifteen highly trained distance runners (seven male; eight female) completed a single running test composed of 4 × 9-min interval series at fixed percentages of body weight ranging from 0 to 30% body weight support (BWS) in 10% increments on LBPPT. The first interval was always conducted at 0% BWS; thereafter, intervals at 10, 20, and 30% BWS were conducted in random order. Each interval consisted of three stages of 3 min each, at velocities of 14.5, 16.1, and 17.7 km·h⁻¹ for men and 12.9, 14.5, and 16.1 km·h⁻¹ for women. Expired gases, ventilation, breathing frequency, heart rate (HR), rating of perceived exertion (RPE), and stride characteristics were measured during each running speed and BWS.

Results

Male and female runners had similar physiological and biomechanical responses to running on LBPPT. Increasing BWS increased stride length (p < 0.02) and flight duration (p < 0.01) and decreased stride rate (p < 0.01) and contact time (p < 0.01) in small-large magnitudes. There was a large attenuation of oxygen consumption (VO₂) relative to BWS (p < 0.001), while there were trivial-moderate reductions in respiratory exchange ratio, minute ventilation, and respiratory frequency (p > 0.05), and small-large effects on HR and RPE (p < 0.01). There were trivial-small differences in V_E, respiratory frequency, HR, and RPE for a given VO₂ across various BWS (p > 0.05).

Conclusions

The results indicate the male and female distance runners have similar physiological and biomechanical responses to LBPPT running. Overall, the biomechanical changes during LBPPT running all contributed to less metabolic cost and corresponding physiological changes.

Analysis of the relationships that body composition and muscular strength have with oxygen cost of walking in children with cerebral palsy

OBJECTIVE

To investigate whether body composition and lower extremity strength relate to oxygen cost of walking in children with cerebral palsy (CP), and to evaluate the relative contributions of these measures to explain variation in oxygen cost seen in this population.

METHODS

A total of 116 children with spastic diplegic CP, Gross Motor Function Classification System levels I-III, aged 8-18 participated. Strength, body composition (body mass index (BMI) and percent body fat) and oxygen cost were recorded. Pearson correlations assessed relationships between variables of body composition and strength to oxygen cost. Forward stepwise linear regression analyzed variance explained by strength and body composition measures. Oxygen data were analyzed by weight status classifications using one-way analysis of variance with significance set at p<0.05.

RESULTS

Total strength (r=-0.27) and total extensor strength (r=-0.27) had fair inverse relationships with oxygen cost. Total extensor strength explained 7.5% (r(2)=0.075, beta=-0.274, p<0.01) of the variance in oxygen cost. Body composition did not explain significant variance in oxygen cost, however significant differences were found in oxygen consumption (p=0.003) and walking velocity (p=0.042) based on BMI weight classifications.

CONCLUSIONS

For ambulatory children with CP, oxygen cost during walking can be partially explained by total extensor strength and not body composition. However, those categorized as obese may adjust to a slower walking speed to keep their oxygen cost sustainable, which may further affect their ability to keep up with typically developing peers and possibly lead to greater fatigue.

Submaximal oxygen cost during incremental exercise in children with developmental coordination disorder

There has been minimal evidence examining the differences in submaximal aerobic power between children with and without probable developmental coordination disorder (pDCD). This is important as most activities of daily living are performed at submaximal levels. The aim of this study was to examine the oxygen cost of work (VO2) performed during an incremental exercise protocol on a cycle ergometer. Subjects with pDCD (n=63) were matched for age and gender to 63 typically developing controls (12-13 years of age) using a nested case-control design. Motor coordination was assessed using the Movement Assessment Battery for Children. Children with pDCD had significantly lower VO2 peak values relative to controls (35.0 vs. 42.9 ml/kg/min, p<0.0001). At the submaximal level, mixed effects modeling demonstrated that, after controlling for relative body fat, and VO2 peak, children with pDCD had consistently greater oxygen cost (VO2 ml/kg/min) compared to controls at any given exercise intensity (p=0.0006). A significant interaction between pDCD and workload indicated that the difference in VO2 at higher workloads is greater than that at lower workloads (p=0.0004). Children with pDCD utilize more oxygen to sustain the same submaximal workload. The implication of these findings is that children with pDCD may experience earlier fatigue than well coordinated individuals when engaging in physical activity.