Arch Stiffness Does Not Determine Running Economy in Recreational Runners

The primary purpose of this study was to determine the relationship between foot length, arch stiffness, and running economy in recreational runner at low running velocities. Sixteen trained endurance (age 20.5 ± 0.4 yrs, height 172 ± 1.8 cm, and mass 68.53 ± 2.40 kg) athletes had their foot anthropometrics and running economy measured. Foot anthropometrics including Foot Length (FL), Arch Stiffness Index (ASI), and Achilles Tendon Moment Arm Length (ATML) were assessed. Subjects then completed a maximal oxygen consumption (VO_2max) test and running economy (RE) assessment. RE was measured as the oxygen consumption during running at velocities of 9.9 km/h and 11.9 km/h at a 1% grade. Data is reported as Mean ± SE, and the relationship between foot anthropometrics and running economy was assessed with linear regression (α = 0.05). Results: Absolute and relative VO_2max values were 3.68 ± 0.19 L/min and 52.96 ± 1.51 mL/kg/min. ASI was 1513 ± 174.27 A.U. with a standing foot length of 25.41 ± 0.4 cm. Subject oxygen consumption at 9.9 km/h and 11.9 km/h was 34.9 ± 0.80 mL/kg/min and 41.02 ± 0.82 mL/kg/min, respectively. There was no correlation between ASI, FL, AHI, and RE (p > 0.05). Arch stiffness and Achilles tendon moment arm do not determine running economy. Therefore, running economy may be impacted by other physiological and biomechanical factors at low running velocities.

Efficiency of cycling exercise: Quantification, mechanisms, and misunderstandings

The energetics of cycling represents a well-studied area of exercise science, yet there are still many questions that remain. Efficiency, broadly defined as the ratio of energy output to energy input, is one key metric that, despite its importance from both a scientific as well as performance perspective, is commonly misunderstood. There are many factors that may affect cycling efficiency, both intrinsic (e.g., muscle fiber type composition) and extrinsic (e.g., cycling cadence, prior exercise, and training), creating a complex interplay of many components. Due to its relative simplicity, the measurement of oxygen uptake continues to be the most common means of measuring the energy cost of exercise (and thus efficiency); however, it is limited to only a small proportion of the range of outputs humans are capable of, further limiting our understanding of the energetics of high-intensity exercise and any mechanistic bases therein. This review presents evidence that delta efficiency does not represent muscular efficiency and challenges the notion that the slow component of oxygen uptake represents decreasing efficiency. It is noted that gross efficiency increases as intensity of exercise increases in spite of the fact that fast-twitch fibers are recruited to achieve this high power output. Understanding the energetics of high-intensity exercise will require critical evaluation of the available data.

The Best Choice of Oxygen Cost Prediction Equation for Computing Post-Stroke Walking Energy Expenditure Using an Accelerometer

BACKGROUND

The integration of oxygen cost into the accelerometer's algorithms improves accuracy of total energy expenditure (TEE) values as post-stroke individuals walk. Recent work has shown that oxygen cost can be estimated from specific prediction equations for stroke patients.

OBJECTIVE

The objective is to the validity of the different oxygen cost estimation equations available in the literature for calculating TEE using ActigraphGT3x as individuals with stroke sequelae walk.

METHOD

Individuals with stroke sequelae who were able to walk without human assistance were included. The TEE was calculated by multiplying the walking distance provided by an ActigraphGT3x worn on the healthy ankle and the patient's oxygen cost estimated from the selected prediction equations. The TEE values from each equation were compared to the TEE values measured by indirect calorimetry. The validity of the prediction methods was evaluated by Bland-Altman analysis (mean bias (MB) and limits of agreement (LoA) values).

RESULTS

We included 26 stroke patients (63.5 years). Among the selected equations, those of Compagnat and Polese obtained the best validity parameters for the ActigraphGT3x: MB_Compagnat = 1.2 kcal, 95% LoA_Compagnat = [-12.0; 14.3] kcal and MB_Polese = 3.5 kcal, 95% LoA_Polese = [-9.2; 16.1] kcal. For comparison, the estimated TEE value according to the manufacturer's algorithm reported MB_Manufacturer = -15 kcal, 95% LoA_Manufacturer = [-52.9; 22.8] kcal.

CONCLUSION

The Polese and Compagnat equations offer the best validity parameters in comparison with the criterion method. Using oxygen cost prediction equations is a promising approach to improving assessment of TEE by accelerometers in post-stroke individuals.

Characterising running economy and change of direction economy between soccer players of different playing positions, levels and sex

Traditional movement economy (ME) measures the energetic cost of in-line running. However, it is debatable whether such a measure is representative of movement efficiency for team sport athletes who are required to run and change direction repeatedly. This study evaluated ME during both in-line running and runs with directional changes and provided a preliminary exploration as to whether these abilities discriminate soccer players according to playing position, level, and sex. Forty-three soccer players were assessed for ME as extrapolated from oxygen uptake during in-line running (RE) and running with changes of directions (using 20 and 10 m shuttle runs [SRE₂₀ and SRE₁₀]) at 8.4 km/h mean speed. ME worsened with change of direction frequency (p < 0.001). Coefficient of determination was high between RE and SRE₂₀ (r²=0.601) but dropped below 0.5 for RE and SRE₁₀ (r² = 0.280) as change of direction frequency increased. No significant differences were observed between different player positions, however, centre midfielders reported the best ME across any position and running mode, with the largest differences observed in centre backs over SRE₁₀ (41.9 ± 2.7 ml/kg/min [centre midfielders] vs 45 ± 1.8 ml/kg/min [centre backs]; ES = 1.19). No significant differences were observed for ME over any running condition for male players of different playing levels. Female players exhibited better ME than male players with significant differences observed for SRE₁₀ (41.5 ± 2.6 ml/kg/min [females] vs 44 ± 2.6 ml/kg/min [males]; p = 0.013; ES = 0.94). RE does not adequately account for efficiency during activities that involve changes of direction. SRE₁₀ is a stronger discriminator of ME between soccer players of different position and sex.

Moderate-intensity exercise with blood flow restriction on cardiopulmonary kinetics and efficiency during a subsequent high-intensity exercise in young women: A cross-sectional study

Blood flow restriction (BFR) training applied prior to a subsequent exercise has been used as a method to induce changes in oxygen uptake pulmonary kinetics (O2P) and exercise performance. However, the effects of a moderate-intensity training associated with BFR on a subsequent high-intensity exercise on O2P and cardiac output (QT) kinetics, exercise tolerance, and efficiency remain unknown.This prospective physiologic study was performed at the Exercise Physiology Lab, University of Brasilia. Ten healthy females (mean ± SD values: age = 21.3 ± 2.2 years; height = 1.6 ± 0.07 m, and weight = 55.6 ± 8.8 kg) underwent moderate-intensity training associated with or without BFR for 6 minutes prior to a maximal high-intensity exercise bout. O2P, heart rate, and QT kinetics and gross efficiency were obtained during the high-intensity constant workload exercise test.No differences were observed in O2P, heart rate, and QT kinetics in the subsequent high-intensity exercise following BFR training. However, exercise tolerance and gross efficiency were significantly greater after BFR (220 ± 45 vs 136 ± 30 seconds; P < .05, and 32.8 ± 6.3 vs 27.1 ± 5.4%; P < .05, respectively), which also resulted in lower oxygen cost (1382 ± 227 vs 1695 ± 305 mL min-1).We concluded that moderate-intensity BFR training implemented prior to a high-intensity protocol did not accelerate subsequent O2P and QT kinetics, but it has the potential to improve both exercise tolerance and work efficiency at high workloads.

Effect of Carbohydrate Content in a Pre-event Meal on Endurance Performance-Determining Factors: A Randomized Controlled Crossover-Trial

The current study aimed to investigate the effect of the relative CHO content in a pre-event meal on time to exhaustion (TTE), peak oxygen uptake (V∙O2peak), the 2nd lactate threshold (LT2), onset of blood lactate accumulation (OBLA), and work economy (WE) and to compare responses between well-trained and recreationally trained individuals. Eleven well-trained and 10 recreationally trained men performed three trials in a randomized cross-over design, in which they performed exercise tests (1) after a high-CHO pre-event meal (3 g · kg⁻¹), (2) a low-CHO pre-event meal (0.5 g · kg⁻¹), or (3) in a fasted-state. The test protocol consisted of five submaximal 5-min constant-velocity bouts of increasing intensity and a graded exercise test (GXT) to measure TTE. A repeated measure ANOVA with a between-subjects factor (well-trained vs. recreational) was performed. A main effect of pre-event meal was found (p = 0.001), with TTE being 8.0% longer following the high-CHO meal compared to the fasted state (p = 0.009) and 7.2% longer compared to the low-CHO meal (p = 0.010). No significant effect of pre-event meal on V∙O2peak, LT2, OBLA, or WE (p ≥ 0.087) was found and no significant interaction effect between training status and pre-event CHO intake was found for TTE or any of the performance-determining variables (p ≥ 0.257). In conclusion, high-CHO content in the pre-event meal led to a longer TTE compared to a meal with a low-CHO content or exercising in a fasted state, both in well-trained and recreationally trained participants. However, the underlying physiological reason for the increased TTE is unclear, as no effect of pre-event meal on the main physiological performance-determining variables was found. Thus, pre-event CHO intake should be standardized when the goal is to assess endurance performance but seems to be of less importance when assessing the main performance-determining variables.

The Effects of L-Citrulline on Blood-Lactate Removal Kinetics Following Maximal-Effort Exercise

The accumulation of lactate in muscle and blood during high-intensity exercise is negatively correlated with the duration exercise can be sustained. Removal of lactate is a key component of acute recovery between consecutive bouts of such exercise. Low-intensity exercise enhances recovery by accelerating lactate turnover in metabolically active tissues, largely mediated by blood flow to these tissues. Therefore, the purpose of this research was to clarify if L-citrulline, a nutritional supplement purported to promote vasodilation via enhanced nitric oxide availability, would augment the removal of blood lactate during active recovery (AR). L-citrulline ingestion will augment the rate of blood lactate concentration decrease during AR, reduce the oxygen-cost of submaximal exercise, and increase time-to-exhaustion and peak oxygen uptake (V̇O2peak) during a test of maximal aerobic power. Healthy university students (five males & five females) participated in this double-blind, randomized, placebo-controlled study. Participants exercised on a cycle ergometer at submaximal steady-state intensities followed by progressively increasing intensity to exhaustion, 10 min of AR, and then supramaximal intensity exercise to exhaustion. Oxygen uptake was measured throughout the trial and blood lactate was sampled repeatedly during AR. The protocol elicited very high peak blood lactate concentrations after exercise (11.3 + 1.3 mmol/L). L-citrulline supplementation did not significantly alter blood lactate kinetics during AR, the oxygen cost of exercise, V̇O2peak, or time-to-exhaustion. Despite a strong theoretical basis by which L-citrulline could augment lactate removal from the blood, L-citrulline supplementation showed no effect as an exercise-recovery supplement.

Equations for estimating the oxygen cost of walking in stroke patients: a systematic review

OBJECTIVE

To report all equations that can potentially be used to estimate the oxygen cost of walking (Cw) without using a respiratory gas exchange analyzer and to provide the level of reliability of each equation.

DATA SOURCES

Webline, Medline, Scopus, ScienceDirect, Bielefeld Academic Search Engine (BASE), and Wiley Online Library databases from 1950 to August 2019 with search terms related to stroke and oxygen cost of walking.

METHODS

This systematic review was reported according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, and the methodological quality of included studies was determined with the Critical Appraisal Skills Programme (CASP).

RESULTS

We screened 2065 articles, and 33 were included for full-text analysis. Four articles were included in the data synthesis (stroke individuals=184). Analysis reported 4 equations estimating Cw that were developed from logistic regression equations between Cw and self-selected walking speed. The equations differed in several methodological aspects (characteristics of individuals, type of equation, Cw reference measurement methods). The Compagnat et al. study had the highest quality (CASP score=9/9).

CONCLUSIONS

This literature review highlighted 4 equations for estimating Cw from self-selected walking speed. Compagnat et al. presented the best quality parameters, but this work involved a population restricted to individuals with hemispheric stroke sequelae.

The Optimal Weight Carriage System for Runners: Comparison Between Handheld Water Bottles, Waist Belts, and Backpacks

In endurance running, where fluid and nutritional support is not always readily available, the carriage of water and nutrition is essential. To compare the economy and physiological demands of different carriage systems, 12 recreational runners (mean age 22.8 ± 2.2 years, body mass index 24.5 ± 1.8 kg m⁻², VO₂max 50.4 ± 5.3 ml kg⁻¹ min⁻¹), completed four running tests, each of 60-min duration at individual running speeds (mean running speed 9.5 ± 1.1 km h⁻¹) on a motorized treadmill, after an initial exercise test. Either no load was carried (control) or loads of 1.0 kg, in a handheld water bottle, waist belt, or backpack. Economy was assessed by means of energy cost (CR), oxygen cost (O₂ cost), heart rate (HR), and rate of perceived exertion (RPE). CR [F(2,20) = 37.74, p < 0.01, η_p² = 0.79], O₂ cost [F(2,20) = 37.98, p < 0.01, η_p² = 0.79], HR [F(2,18) = 165.62, p < 0.01, η_p² = 0.95], and RPE [F(2,18) = 165.62, p < 0.01, η_p² = 0.95] increased over time, but no significant differences were found between the systems. Carrying a handheld water bottle, waist belt, or backpack, weighing 1.0 kg, during a 60-min run exhibited similar physiological changes. Runners’ choice may be guided by personal preference in the absence of differences in economy (CR, O₂ cost, HR, and RPE).

Influence of Shoe Mass on Performance and Running Economy in Trained Runners

Purpose

The aim of this study was to assess the effects of adding shoe mass on running economy (RE), gait characteristics, neuromuscular variables and performance in a group of trained runners.

Methods

Eleven trained runners (6 men and 5 women) completed four evaluation sessions separated by at least 7 days. The first session consisted of a maximal incremental test where the second ventilatory threshold (VT₂) and the speed associated to the VO_2max (vVO_2max) were calculated. In the next sessions, RE at 75, 85, and 95% of the VT₂ and the time to exhaustion (TTE) at vVO_2max were assessed in three different shoe mass conditions (control, +50 g and +100 g) in a randomized, counterbalanced crossover design. Biomechanical and neuromuscular variables, blood lactate and energy expenditure were measured during the TTE test.

Results

RE worsened with the increment of shoe mass (Control vs. 100 g) at 85% (7.40%, 4.409 ± 0.29 and 4.735 ± 0.27 kJ⋅kg⁻¹⋅km⁻¹, p = 0.021) and 95% (10.21%, 4.298 ± 0.24 and 4.737 ± 0.45 kJ⋅kg⁻¹⋅km⁻¹, p = 0.005) of VT₂. HR significantly increased with the addition of mass (50 g) at 75% of VT₂ (p = 0.01) and at 75, 85, and 95% of VT₂ (p = 0.035, 0.03, and 0.03, respectively) with the addition of 100 g. TTE was significantly longer (∼22%, ∼42 s, p = 0.002, ES = 0.149) in the Control condition vs. 100 g condition, but not between Control vs. 50 g (∼24 s, p = 0.094, ES = 0.068).

Conclusion

Overall, our findings suggest that adding 100 g per shoe impairs running economy and performance in trained runners without changes in gait characteristics or neuromuscular variables. These findings further support the use of light footwear to optimize running performance.

Running economy in recreational male and female runners with similar levels of cardiovascular fitness

This study explored differences in running economy between well-conditioned young male and female (tested within the early follicular phase of their menstrual cycle) participants, matched for age and percent difference between predicted and actual maximum oxygen uptake (V̇o_2max). Twenty-five recreational runners (13 men and 12 women), aged 19-27 yr, performed graded treadmill exercise to assess V̇o_2max. Participants also performed three bouts of submaximal continuous treadmill running at 8, 10, and 12 km/h. Sex comparisons revealed lower maximal aerobic speed (MAS) and V̇o_2max in women relative to men (P < 0.05). However, the percent difference from predicted V̇o_2max was similar between men and women (men: 149.6 ± 18.7%, women: 150.8 ± 16.4%; P > 0.05). Absolute running economy (mL·kg^-0.75·km^-1) improved in transition between treadmill speeds, and this occurred similarly in both sexes. Despite this, women showed overall lower oxygen cost of running than men during treadmill locomotion at predetermined absolute and relative intensities (P < 0.05). Finally, in a small subset of participants (n = 6, 3 male and 3 female participants) with similar MAS (16 km/h), men still exhibited higher V̇o_2max and gross oxygen cost of running than women (difference of ~6%, statistics not computed). The present results indicate that, in men and women with similar percent of predicted V̇o_2max, running economy follows a sexually dimorphic pattern throughout a broad spectrum of treadmill speeds. Ultimately, from a motor performance perspective, our data strongly suggest that lower V̇o_2max values in female recreational runners are partially compensated by lower gross oxygen cost of locomotion during submaximal running.NEW & NOTEWORTHY Our data demonstrate that, compared with that seen in men with similar percent difference from predicted maximum oxygen uptake (V̇o_2max), scaled gross oxygen cost of running (in absolute and relative terms) is lower in women throughout a broad spectrum of treadmill speeds. Importantly, these findings were obtained after controlling for the effects of the menstrual cycle on running economy, and this is novel.

Running economy and effort after cycling: Effect of methodological choices

Prior exercise can negatively affect movement economy of a subsequent task. However, the impact of cycling exercise on the energy cost of subsequent running is difficult to ascertain, possibly because of the use of different methods of calculating economy. We examined the influence of a simulated cycling bout on running physiological cost (running economy, heart rate and ventilation rates) and perceptual responses (ratings of perceived exertion and effort) by comparing two running bouts, performed before and after cycling using different running economy calculation methods. Seventeen competitive male triathletes ran at race pace before and after a simulated Olympic-distance cycling bout. Running economy was calculated as V̇O₂ (mL∙kg^-1∙min^-1), oxygen cost (EO₂, mL∙kg^-1∙m^-1) and aerobic energy cost (E_aer, J∙kg^-1∙m^-1). All measures of running economy and perceptual responses indicated significant alterations imposed by prior cycling. Despite a good level of agreement with minimal bias between calculation methods, differences (p < 0.05) were observed between E_aer and both V̇O₂ and EO₂. The results confirmed that prior cycling increased physiological cost and perceptual responses in a subsequent running bout. It is recommended that E_aer be calculated as a more valid measure of running economy alongside perceptual responses to assist in the identification of individual responses in running economy following cycling.

Oxygen Cost During Walking in Individuals With Stroke: Hemiparesis Versus Cerebellar Ataxia

Background. Understanding the factors that limit mobility in stroke patients is fundamental for proposing appropriate rehabilitation strategies. A high oxygen cost during walking (Cw) has a strong impact on the community ambulation of hemiparetic patients. The Cw in poststroke cerebellar ataxia is poorly evaluated, unlike hemiparetic gait. Objective. To compare the oxygen cost/self-selected walking speed (S) relationship in stroke individuals with cerebellar ataxia or hemiparetic gait. Methods. Thirty-three subjects were included (14 cerebellar stroke, 19 hemispheric stroke), with stroke confirmed by brain imaging and able to walk without human assistance. We measured Cw using the Metamax3B. The relationship between Cw and self-selected walking speed was modelled by logistic regression and then compared between the cerebellar and hemispheric groups. Results. No significant difference was found between the 2 groups for all characteristics of the population, except motor impairments, spasticity, and ataxia (P < .01). We identified 2 separate Cw/S relationships with different logistic regression equations for the 2 groups. Faster than 0.4 m s⁻¹, Cw was 30.6% to 39.9% higher in patients with cerebellar stroke in comparison with hemispheric stroke individuals. The Cw was correlated with ataxia (r = 0.88; P < .001) in the cerebellar group, whereas there was a correlation with motor impairments (r = −0.61; P < .01), spasticity (r = 0.59; P < .01), and ataxia (r = 0.81; P < .01) in hemispheric stroke individuals. Conclusion. The Cw in poststroke cerebellar ataxia is significantly higher compared with hemiparetic patients at an equivalent walking speed. The impact on community walking needs to be explored in stroke survivors with cerebellar stroke.

Reproducibility of Different Methodologies to Calculate Oxygen Consumption and Oxygen Cost During Walking in Chronic Stroke Survivors

OBJECTIVE

The most common methods to calculate energy costs are based on measured oxygen uptake during walking a standardized distance or time. Unfortunately, it is unclear which method is most reliable to determine energy cost of walking in stroke survivors. The objective of this study was to evaluate the 3 most commonly used methods for calculating oxygen consumption and -cost by assessing test-retest reliability and measurement error in community dwelling chronic stroke survivors during a 6 Minute Walk Test.

METHODS

In this secondary analysis of a longitudinal study, reproducibility of the outcome of walking distance, walking speed, oxygen consumption and oxygen cost from 3 methods (Kendall's tau, assumed steady-state and total walking time oxygen consumption) were determined using Intraclass Correlation Coefficient, Standard Error of Measurement and Smallest Detectable Change.

RESULTS

20 from the 31 participants successfully performed the 6 minute walk test-retest within a timeframe of 1 month. Within the 2 tests the reproducibility of walking distance and walking speed was high. The 3 methods to determine reproducibility for oxygen cost and oxygen consumption were considered good (Kendall's tau), good (assumed steady-state) and excellent (total walking time).

CONCLUSIONS

The method using oxygen consumption and -cost over the total walking time resulted in the highest reproducibility considering the Intraclass Correlation Coefficient, its 95% Confidence Interval, and smaller absolute differences.

Double-Poling Physiology and Kinematics of Elite Cross-Country Skiers: Specialized Long-Distance Versus All-Round Skiers

PURPOSE

Long-distance cross-country skiers specialize to compete in races >50 km predominantly using double poling (DP). This emphasizes the need for highly developed upper-body endurance capacities and an efficient DP technique. The aim of this study was to investigate potential effects of specialization by comparing physiological capacities and kinematics in DP between long-distance skiers and skiers competing using both techniques (skating/classic) in several competition formats ("all-round skiers").

METHODS

Seven male long-distance (32 [6] y, 183 [6] cm, 76 [5] kg) and 6 all-round (25 [3] y, 181 [5] cm, 75 [6] kg) skiers at high international levels conducted submaximal workloads and an incremental test to exhaustion for determination of peak oxygen uptake (VO2peak) and time to exhaustion (TTE) in DP and running.

RESULTS

In DP and running maximal tests, TTE showed no difference between groups. However, long-distance skiers had 5-6% lower VO2peak in running (81 [5] vs 85 [3] mL·kg-1·min-1; P = .07) and DP (73 [3] vs 78 [3] mL·kg-1·min-1; P < .01) than all-round skiers. In DP, long-distance skiers displayed lower submaximal O2 cost than all-round skiers (3.8 ± 3.6%; P < .05) without any major differences in cycle times or cyclic patterns of joint angles and center of mass. Lactate concentration over a wide range of speeds (45-85% of VO2peak) did not differ between groups, even though each workload corresponded to a slightly higher percentage of VO2peak for long-distance skiers (effect size: 0.30-0.68).

CONCLUSIONS

The long-distance skiers displayed lower VO2peak but compensated with lower O2 cost to perform equally with the all-round skiers on a short TTE test in DP. Furthermore, similar submaximal lactate concentration and reduced O2 cost could be beneficial in sustaining high skiing speeds in long-duration competitions.

Effect of Different Seat Heights during an Incremental Sit-To-Stand Exercise Test on Peak Oxygen Uptake in Young, Healthy Women

'Sit-to-stand' exercise uses the repetitive motion of standing up and sitting down in a chair, a common activity of daily living. A new assessment using an incremental sit-to-stand exercise test employs an external sound to control the speed of standing-up and allows increases in work rate. The aims of the study were to examine the effect of different seat heights on peak oxygen uptake (peak VO2) during an incremental sit-to-stand exercise and to assess any difference between peak VO2 values during incremental sit-to-stand exercise compared with a cycle ergometer test. Thirteen healthy young women (age: 23.1 ± 2.6 years, height: 1.61 ± 0.06 m, body mass: 51.9 ± 7.4 kg·m-2) participated in four incremental sit-to-stand tests with different seat heights and cycle tests in random order. The seat heights were adjusted to 100%, 80%, 120%, and 140% of knee height distance (100%, 80%, 120%, and 140% incremental sit-to-stand exercise, respectively). The peak VO2 and completion time were measured during incremental sit-to-stand and cycle ergometer tests, and repeated-measures analysis of variance and Student's paired t-test with Holm's method were used to evaluate differences between these variables. The peak VO2 values increased by about 10-12 mL·min-1·kg-1 as the seat height on the ISTS decreased over a 60% range of lower leg lengths. The peak VO2 values on the 80%, 100%, 120%, and 140% incremental sit-to-stand tests were about 11%, 25%, 40%, and 50% lower than that on the cycle ergometer test, respectively. The peak VO2 on the incremental sit-to-stand test increased as seat height decreased. These findings are useful to determine which seat height on the incremental sit-to-stand tests test is suitable for different populations.

The African disability scooter: efficiency testing in paediatric amputees in Malawi

Purpose: The African Disability Scooter (ADS) was developed for lower limb amputees, to improve mobility and provide access to different terrains. The aim of this study was to test the efficiency of the ADS in Africa over different terrains. Method: Eight subjects with a mean age of 12 years participated. Energy expenditure and speed were calculated over different terrains using the ADS, a prosthetic limb, and crutches. Repeated testing was completed on different days to assess learning effect. Results: Speed was significantly faster with the ADS on a level surface compared to crutch walking. This difference was maintained when using the scooter on rough terrain. Oxygen cost was halved with the scooter on level ground compared to crutch walking. There were no significant differences in oxygen consumption or heart rate. There were significant differences in oxygen cost and speed between days using the scooter over level ground, suggesting the presence of a learning effect. Conclusions: This study demonstrates that the ADS is faster and more energy efficient than crutch walking in young individuals with amputations, and should be considered as an alternative to a prosthesis where this is not available. The presence of a learning effect suggests supervision and training is required when the scooter is first issued.

Implications for Rehabilitation

The African Disability Scooter:

is faster than crutch walking in amputees;

is more energy efficient than walking with crutches;

supervised use is needed when learning to use the device;

is a good alternative/adjunct for mobility.

Walking, orthoses and physical effort in a Swedish population with arthrogryposis

PURPOSE

Excessive movements during walking have been observed by gait analysis in children with arthrogryposis (AMC) using orthoses compared to children using only shoes. The aim of this study was to evaluate energy expenditure and functional exercise capacity in children with AMC.

METHODS

Twenty-four children with AMC and 25 typically developing (TD) children underwent oxygen measurement and the 6-minute walk test (6MWT). Children were divided into AMC1 using knee-ankle-foot orthoses with locked knee joints (KAFO-LK); AMC2 KAFOs with open knee joints (KAFO-O) or ankle-foot orthoses (AFO); and AMC3 using shoes.

RESULTS

The net non-dimensional oxygen cost (NNcost) was lower in TD (0.308) than in AMC2 (0.455, n = 10) (p = 0.002). There were no differences in the net non-dimensional consumption (NNconsumption) or normalised walking velocity. The lowest NNconsumption (0.082), NNcost (0.385) and normalised walking velocity (0.214) were found in AMC1 (n = 3), but no statistical calculation was performed. In the 6MWT, both AMC2 (402.7, n = 11) and AMC3 (476.8, n = 10) walked shorter distances (m) than TD (565.1) (p < 0.001 and p = 0.043, respectively). AMC2 (0.435) had lower normalised walking velocity than TD (0.564) (p < 0.001).

CONCLUSIONS

Children with AMC using open KAFOs or AFOs (AMC2) had higher energy effort represented by significantly higher NNcost than TD, whereas AMC children requiring only shoes (AMC3) did not differ significantly from TD. To maintain the NNconsumption at an acceptable level, children using locked KAFOs (AMC1) slowed down their walking velocity. Compared to TD, the exercise capacity was lower in children with AMC using open KAFOs or AFOs and shoes, represented by lower walking velocity and shorter distance walked during the 6MWT.

Oxygen cost during treadmill walking with hip and knee immobilised

The aim of this study was to determine the effect of immobilising the knee and hip on the oxygen cost (ml·kg(-1)·min(-1)) to velocity relationship during treadmill walking. The study was a prospective experimental conducted in a Rehabilitation centre. Ten healthy individuals, five men and five women, with no gait abnormality participated. Following familiarisation five men and five women walked on a treadmill and selected their own, free "comfortable walking velocity "(SSWS). Subjects then performed an incremental test at -60 to +60% of SSWS. Individuals later repeated the test with the knee and hip of one limb immobilised. Samples of expired air were measured at each velocity and the oxygen cost (ml·kg(-1)·min(-1)) to Froude number (Fr) relationship plotted (where calculation of Fr normalizes for subjects of differing leg length and acts as an index of velocity). There was a higher oxygen cost, and lower Fr at SSWS during immobilised (0.21 ± 0.03 ml·kg(-1)·min(-1); Fr = 0.12 ± 0. 03) compared with free walking (0.16 ± 0.02 ml·kg(-1)·min(-1); Fr = 0.18 ± 0.04) (p < 0. 01). Statistical analysis demonstrated that during immobilised walking an inverse fit (y = β0 + β1/x) and for free walking a cubic fit (y = β0 + β1x + β2x(2) + β3x(3) ) best fitted the data. Hip and knee immobilisation increased the oxygen cost at SSWS and altered the oxygen cost to Fr relationship. The results have implications in selecting optimal walking velocities in individuals with impairments affecting mobility such as hemiplegic gait. Key PointsWalking with one limb immobilised requires greater energy cost than normal free walking.This has clinical implications when developing rehabilitation strategies for patients who mobility problems such as those with hemi paretic gait.