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Purpose: Recent studies have suggested that turning is power intensive. Given the sporadic and irregular movement patterns of children, such findings have important implications for the assessment of true energy expenditure associated with habitual physical activity. The purpose of this study was to investigate the influence of walking speed and angle, and their interaction, on the energy expenditure of healthy children.Methods: 20 children (10.1 ± 0.5 years; 10 boys) participated in the study. On two separate days, participants completed a turning protocol involving 3-min bouts of walking at one of the 16 speed (2.5, 3.5, 4.5, and 5.5 km h- 1) and angle (0°, 45°, 90°, and 180°) combinations, interspersed by 3 min seated rest. The movement involved 5 m straight walking interspaced with prescribed turns with speed dictated by a digital, auditory metronome. Breath-by-breath gas exchange was measured, in addition to tri-axial acceleration and magnetic field intensity recorded at 100 Hz.Results: Mixed models revealed a significant main effect for speed (p < 0.006) and angle (p < 0.006), with no significant interaction between speed and angle (p > 0.006). Significant differences to straight-line walking energy expenditure within speed were established for 3.5 and 5.5 km h- 1 for 180° turns (~ 13% and ~ 30% increase, respectively).Conclusion: These findings highlight the importance of accounting for the magnitude and frequency of turns completed when estimating children's habitual physical activity and have significant implications for the assessment of daily energy expenditure. [ABSTRACT FROM AUTHOR]

Purpose: Oxidative stress is associated with tissue cytokine secretion although the precise mechanism(s) underpinning this relationship during high intensity intermittent exercise remains unclear. This study investigates the acute response to a bout of high intensity intermittent walking (HIIW), compared to continuous moderate intensity walking (CMW), on various cytokines and biomarkers of oxidative stress.Methods: Seventeen (n = 17) apparently healthy male participants (aged 22.6 ± 4.6 years; [Formula: see text]: 53.7 ± 7.1 ml kg-1 min-1) undertook a randomised crossover study consisting of two exercise trials: (1) HIIW requiring 3 × 5 min bursts at 80% [Formula: see text] (each separated by 5 min of walking at 30% [Formula: see text]) and (2) CMW (60% [Formula: see text] for 30 min). Each trial was separated by 7 days. Venous blood samples were obtained pre-exercise, post-exercise and at 2, 4, 24 and 48 h post-exercise for determination of systemic inflammation (IL-6 and TNF-α), lipid soluble antioxidants and oxidative stress (LOOH, H2O2 and the ascorbyl free radical).Results: Both IL-6 and TNF-α increased immediately post exercise, regardless of intensity and remained elevated until at least 4 h (main effect for time; p < 0.05). While there was no change in either lipid peroxidation or free radical metabolism (Asc· and H2O2), α-tocopherol increased (pooled HIIW and CMW, p < 0.05), whereas lycopene decreased at 2 h post HIIW (p < 0.05).Conclusion: Bouts of both HIIW and CMW promote cytokine secretion post exercise, and this seems to be independent of oxidative stress. Further investigation is required to assess how such changes may underpin some of the transient health benefits of exercise. [ABSTRACT FROM AUTHOR]

Purpose: Our aim was to examine whether cognitive processing during walking increases the metabolic cost of transport in healthy young adults.Methods: Twenty healthy, young adults completed five conditions: (1) walking at a self-selected speed (spontaneous single-task), (2) seated resting (baseline), (3) performing cognitive task while seated (cognitive single-task), (4) walking while simultaneously performing the cognitive task (dual-task), and (5) single-task walking at a speed that matched the participant's dual-task gait speed (matched single-task). Rate of oxygen consumption (V̇O2) was recorded during all conditions. Gait speed and cost of walking (Cw; oxygen consumed per distance traveled) were recorded during all walking conditions. Reaction time and accuracy of responses in the cognitive task were recorded during all cognitive task conditions. Data from the fifth minute of each 5-min condition were analyzed.Results: There was no difference in V̇O2 between the dual-task and matched single-task walking conditions. V̇O2 in the seated cognitive condition was significantly smaller than both walking conditions, but was not significantly different than zero. Cw was significantly greater during the matched single-task walking condition than during the dual-task walking condition. However, the difference in Cw was so small that it is unlikely to be clinically significant (0.008 mLO2/kg/m, 95% CI 0.002-0.014).Conclusions: Cognitive processing while walking may not increase energy demands of walking in healthy young adults. Maintaining non-preferred gait speed (matched speed) overground continuously for 5 min may require attentional resources, and thereby increase metabolic costs relative to walking at habitual speed. [ABSTRACT FROM AUTHOR]

Purpose: We developed a short-interval, low-intensity, slow-jogging (SJ) program consisting of sets of 1 min of SJ at walking speed and 1 min of walking. We aimed to examine the effects of an easily performed SJ program on skeletal muscle, fat infiltration, and fitness in older adults.Methods: A total of 81 community-dwelling, independent, older adults (70.8 ± 4.0 years) were randomly assigned to the SJ or control group. The SJ group participants were encouraged to perform 90 min of SJ at their anaerobic threshold (AT) intensity and 90 min of walking intermittently per week. Aerobic capacity at the AT and sit-to-stand (STS) scores were measured. Intracellular water (ICW) in the legs was assessed by segmental multi-frequency bioelectrical impedance analysis. Subcutaneous (SAT) and intermuscular (IMAT) adipose tissue and muscle cross-sectional area (CSA) were measured at the mid-thigh using computed tomography.Results: A total of 75 participants (37 SJ group, 38 controls) completed the 12-week intervention. The AT and STS improved in the SJ group compared with the controls (AT 15.7 vs. 4.9 %, p < 0.01; STS 12.9 vs. 4.5 %, p < 0.05). ICW in the upper leg increased only in the SJ group (9.7 %, p < 0.05). SAT and IMAT were significantly decreased only in the SJ group (p < 0.01).Conclusion: The 12-week SJ program was easily performed by older adults with low skeletal muscle mass, improved aerobic capacity, muscle function, and muscle composition in older adults. [ABSTRACT FROM AUTHOR]

Purpose: Gait speed is associated with survival in older adults and it was suggested that an elevated energy cost of walking (Cw) is an important determinant of gait speed reduction. Thus far, little is known about the factors that contribute to a lower Cw but it was shown that lower body strength training could reduce the Cw. Therefore, the objective of this study was to investigate the relationship between lower body strength and the Cw in a cohort of healthy older adults.Methods: A total of 48 participants were included in this study (70.7 ± 5.4 years). After a geriatric and a neuropsychological assessment, participants underwent a fitness testing protocol which included a maximal oxygen uptake test, assessment of the Cw at 4 km h-1 on a treadmill, an isokinetic maximal strength test for the ankle, knee and hip joints and a body composition assessment. Relationships between strength variables and the Cw were assessed with partial correlations and linear regression analyses.Results: Hip extensors and hip flexors peak torque was significantly correlated with the Cw (r = -0.36 and -0.32, respectively; p < 0.05). A tendency towards significance was identified for the ankle plantar flexors (r = -0.25, p = 0.09). Hip extensors peak torque was the only significant neuromuscular parameter included in the linear regression analysis (p < 0.05).Conclusion: These results show that hip extensors are an important muscle group with regards to the Cw measured on a treadmill in this cohort of healthy older adults. [ABSTRACT FROM AUTHOR]

Purpose: Heart disease risk is elevated in South Asians possibly due to impaired postprandial metabolism. Running has been shown to induce greater reductions in postprandial lipaemia in South Asian than European men, but the effect of walking in South Asians is unknown.Methods: Fifteen South Asian and 14 white European men aged 19-30 years completed two, 2-day trials in a randomised crossover design. On day 1, participants rested (control) or walked for 60 min at approximately 50 % maximum oxygen uptake (exercise). On day 2, participants rested and consumed two high-fat meals over a 9-h period during which 14 venous blood samples were collected.Results: South Asians exhibited higher postprandial triacylglycerol [geometric mean (95 % confidence interval) 2.29 (1.82 to 2.89) vs. 1.54 (1.21 to 1.96) mmol L(-1) h(-1)], glucose [5.49 (5.21 to 5.79) vs. 5.05 (4.78 to 5.33) mmol L(-1) h(-1)], insulin [32.9 (25.7 to 42.1) vs. 18.3 (14.2 to 23.7) µU mL(-1) h(-1)] and interleukin-6 [2.44 (1.61 to 3.67) vs. 1.04 (0.68 to 1.59) pg mL(-1) h(-1)] than Europeans (all ES ≥ 0.72, P ≤ 0.03). Between-group differences in triacylglycerol, glucose and insulin were not significant after controlling for age and percentage body fat. Walking reduced postprandial triacylglycerol [1.79 (1.52 to 2.12) vs. 1.97 (1.67 to 2.33) mmol L(-1) h(-1)] and insulin [21.0 (17.0 to 26.0) vs. 28.7 (23.2 to 35.4) µU mL(-1) h(-1)] (all ES ≥ 0.23. P ≤ 0.01), but group differences were not significant.Conclusions: Healthy South Asians exhibited impaired postprandial metabolism compared with white Europeans, but these differences were diminished after controlling for potential confounders. The small-moderate reduction in postprandial triacylglycerol and insulin after brisk walking was not different between the ethnicities. [ABSTRACT FROM AUTHOR]

Purpose: Light-load blood flow restriction exercise (BFRE) may provide a novel training method to limit the effects of age-related muscle atrophy in older adults. Therefore, the purpose of this study was to compare the haemodynamic response to resistance and aerobic BFRE between young adults (YA; n = 11; 22 ± 1 years) and older adults (OA; n = 13; 69 ± 1 years).Method: On two occasions, participants completed BFRE or control exercise (CON). One occasion was leg press (LP; 20 % 1-RM) and the other was treadmill walking (TM; 4 km h(-1)). Haemodynamic responses (HR, Q, SV and BP) were recorded during baseline and exercise.Result: At baseline, YA and OA were different for some haemodynamic parameters (e.g. BP, SV). The relative responses to BFRE were similar between YA and OA. Blood pressures increased more with BFRE, and also for LP over TM. Q increased similarly for BFRE and CON (in both LP and TM), but with elevated HR and reduced SV (TM only).Conclusion: While BFR conferred slightly greater haemodynamic stress than CON, this was lower for walking than leg-press exercise. Given similar response magnitudes between YA and OA, these data support aerobic exercise being a more appropriate BFRE for prescription in older adults that may contribute to limiting the effects of age-related muscle atrophy. [ABSTRACT FROM AUTHOR]

Purpose: The present study compared the acute effect of 30 min of accumulated versus continuous brisk walking on insulin sensitivity estimated in the fasted state and after an oral glucose tolerance test (OGTT) in young, healthy Asians. Methods: Twenty-five healthy participants (12 males) were provided an OGTT the morning after: (i) accumulating three 10 min bouts of walking the previous evening; (ii) walking continuously for 30 min the previous evening or; (iii) resting the previous evening. Blood samples were taken in the fasted state and for 2 h post-OGTT. Insulin sensitivity was estimated from fasting blood glucose and insulin using the quantitative insulin sensitivity check index (QUICKI) and in response to the OGTT using an insulin sensitivity index (ISI-Matsuda). Results: Fasting insulin was lower after continuous ( P = 0.006) but not accumulated ( P = 0.371) walking versus rest and did not differ between walking trials ( P = 0.554). Similarly, QUICKI [Accumulated 0.381 (0.026) vs. Continuous 0.388 (0.029) vs. Rest 0.371 (0.031)] improved only with continuous ( P = 0.006) and not accumulated walking ( P = 0.255) compared with rest. There was a significant difference in ISI-Matsuda among groups [Accumulated 7.07 (3.04) vs. Continuous 7.29 (2.81) vs. Rest 6.14 (2.46), P = 0.050] with a Bonferroni t test suggesting this was between continuous walking and rest ( P = 0.081). Conclusions: These findings demonstrate that 30 min of brisk walking is sufficient to improve insulin sensitivity in healthy, young Asians but only continuous and not accumulated walking provides this benefit. Further studies are needed to determine if accumulated and continuous exercise have different chronic effects on insulin sensitivity. [ABSTRACT FROM AUTHOR]

Muscle-wasting in chronic kidney disease (CKD) arises from several factors including sedentary behaviour and metabolic acidosis. Exercise is potentially beneficial but might worsen acidosis through exercise-induced lactic acidosis. We studied the chronic effects of exercise in CKD stage 4-5 patients (brisk walking, 30 min, 5 times/week), and non-exercising controls; each group receiving standard oral bicarbonate (STD), or additional bicarbonate (XS) (Total n = 26; Exercising + STD n = 9; Exercising +XS n = 6; Control + STD n = 8; Control + XS n = 3). Blood and vastus lateralis biopsies were drawn at baseline and 6 months. The rise in blood lactate in submaximal treadmill tests was suppressed in the Exercising + XS group. After 6 months, intramuscular free amino acids (including the branched chain amino acids) in the Exercising + STD group showed a striking chronic depletion. This did not occur in the Exercising + XS group. The effect in Exercising + XS patients was accompanied by reduced transcription of ubiquitin E3-ligase MuRF1 which activates proteolysis via the ubiquitin-proteasome pathway. Other anabolic indicators (Akt activation and suppression of the 14 kDa actin catabolic marker) were unaffected in Exercising + XS patients. Possibly because of this, overall suppression of myofibrillar proteolysis (3-methylhistidine output) was not observed. It is suggested that alkali effects in exercisers arose by countering exercise-induced acidosis. Whether further anabolic effects are attainable on combining alkali with enhanced exercise (e.g. resistance exercise) merits further investigation. [ABSTRACT FROM AUTHOR]

Body mass (BM) is a confounding variable in human performance. We hypothesized that adjusting 6-min walk distance (6MWD) for BM differences using allometric scaling would allow meaningful individual and group comparisons. We aimed to use allometric scaling of 6MWD to BM to provide an index for comparing walking performance in middle-aged and older adults. One hundred and twenty subjects (40-87 years) participated. Anthropometry, spirometry, and two walk tests were evaluated. We adjusted 6MWD to BM, gender, and age using an allometric procedure. The allometric exponents were prospectively applied in a validation sample of 44 healthy subjects. Body mass presented significant negative correlation ( p < 0.01) with 6MWD · BM in middle-aged and older adults ( r = −0.70 and −0.46, respectively). The allometric exponent ( b) for 6MWD was significantly higher for older than middle-aged adults (0.35 ± 0.20 vs. 0.11 ± 0.08, respectively). The resulting BM exponents were similar in male and female subjects (0.22 ± 0.13 and 0.17 ± 0.09, respectively). The correlation between 6MWD · BM and BM using the exponents (0.11 or 0.35) was not statistically different from zero ( r = 0.00) in the validation sample, suggesting that allometric analysis did not penalize the subjects based on BM. Allometric scaling of 6MWD in middle-aged and older adults may be useful for evaluating walking performance free of the confounding effect of BM, even in the absence of a table of norms. [ABSTRACT FROM AUTHOR]

Locomotor respiratory coupling patterns in humans have been assessed on the basis of the interaction between different physiological and motor subsystems; these interactions have implications for movement economy. A complex and dynamical systems framework may provide more insight than entrainment into the variability and adaptability of these rhythms and their coupling. The purpose of this study was to investigate the relationship between steady state locomotor-respiratory coordination dynamics and oxygen consumption $$ (\dot{V}O_{2}) $$ of the movement by varying walking stride frequency from preferred. Twelve male participants walked on a treadmill at a self-selected speed. Stride frequency was varied from −20 to +20% of preferred stride frequency (PSF) while respiratory airflow, gas exchange variables, and stride kinematics were recorded. Discrete relative phase and return map techniques were used to evaluate the strength, stability, and variability of both frequency and phase couplings. Analysis of $$ \dot{V}{\text{O}}_{2} $$ during steady-state walking showed a U-shaped response ( P = 0.002) with a minimum at PSF and PSF − 10%. Locomotor-respiratory frequency coupling strength was not greater ( P = 0.375) at PSF than any other stride frequency condition. The dominant coupling across all conditions was 2:1 with greater occurrences at the lower stride frequencies. Variability in coupling was the greatest during PSF, indicating an exploration of coupling strategies to search for the coupling frequency strategy with the least oxygen consumption. Contrary to the belief that increased strength of frequency coupling would decrease oxygen consumption; these results conclude that it is the increased variability of frequency coupling that results in lower oxygen consumption. [ABSTRACT FROM AUTHOR]

The reduced gait stability and aerobic fitness of people with Down syndrome (DS) may increase their rate of gross oxygen uptake (gross-VO(2)) during over-ground walking. If so, the ACSM equation predicting gross-VO(2) from speed may not be appropriate and an equation specifically for these individuals may be needed. This study therefore examined whether the relationship between gross-VO(2) and speed differs between individuals with and without DS during over-ground walking and attempted to develop a gross-VO(2) prediction equation for people with DS. Gross-VO(2) was measured in 18 persons with DS (24.7 ± 6.8 years; 8 men) and 22 persons without DS (25.9 ± 4.8 years; 9 men) at rest and during five over-ground walking trials, each lasting 6 min, at 0.5, 0.75, 1.0, 1.25, and 1.5 m/s. Multi-level modeling with random intercepts and slopes demonstrated significant effects of speed, group, group-by-speed interaction, and speed squared (P < 0.001). In each group, actual gross-VO(2) did not differ from gross-VO(2) predicted by the regression equation across speeds. Bland-Altman plots showed somewhat greater variability in the difference between actual and predicted gross-VO(2) for participants with DS. Mean absolute error of prediction was 10.75 and 10.67% for participants with and without DS, respectively. In participants with DS, the ACSM formula under-estimated gross-VO(2) across speeds, whereas, in participants without DS, only at 1.5 m/s (P < 0.001). Therefore, individuals with DS show altered curvilinear gross-VO(2) to speed relationship during over-ground walking. The present regression equation appears to offer accurate prediction in people with DS and could be used for prescribing over-ground walking intensities. [ABSTRACT FROM AUTHOR]

The cardio-respiratory (heart rate, HR; oxygen uptake, VO(2;) expired carbon dioxide, VCO(2); ventilation, VE), electromyographic (EMG; medial gastrocnemius, vastus lateralis, rectus femoralis, and anterior tibialis), and perceived exertion (PE) responses during a protocol for the determination of the walk-run transition speed (WRTS) were investigated. From an initial sample of 453 volunteers, 12 subjects matched for age, anthropometric characteristics [height, weight, lower limb length (LLL)], cardio-respiratory fitness (peak oxygen consumption, VO(2peak); ventilatory threshold, VT; maximal HR), and habitual physical activity levels were selected (age = 18.6 ± 0.5 years; height = 174.5 ± 1.4 cm; weight = 66.4 ± 1.1 kg; LLL = 83.3 ± 1.2 cm, VO(2peak) = 52.2 ± 2.2 ml kg(-1) min(-1); VT = 39.8 ± 2.6 ml kg(-1) min(-1)). The highly reproducible WRTS determination protocol (ICC = 0.92; p < 0.0001) consisted in 2-min warm-up at 5.5 km h(-1) followed by increments of 0.1 km h(-1) every 15 s. Between-subjects variability of the measured variables during 24 walking and 12 running velocities (from 80 to 120% of WRTS) was compared to WRTS variation. The coefficient of variation for WRTS was 7.8%, which was within the range of variability for age, anthropometric variables, VO(2peak), and maximal HR (from 5 to 12%). Cardio-respiratory responses at WRTS had a greater variation (VO(2) about 50%; VE/VCO(2) about 35%; VE/VO(2) about 45%; HR about 30%). The highest variation was found for PE (from 70 to 90%) whereas EMG variables showed the lowest variation (from 25 to 30%). Linear regression between EMG series and VO(2) data showed that VO(2) reflected the increase in muscle activity only before the WRTS. These results support the hypothesis that the walk-run transition phenomenon is determined by mechanical variables such as limb length and its relationship to biomechanical model rather than by metabolic factors. [ABSTRACT FROM AUTHOR]

The study investigated the effect of varying pole weights on energy expenditure, upper limb muscle activation and on forces transmitted to the poles during Nordic walking (NW). Twelve women [age = 21 (2) years, body mass = 60.8 (6) kg, height = 1.71 (0.06) m] participated in five 7-min walking tests randomly chosen without poles (W), with normal NW poles (NW) or with added masses of 0.5 kg (NW + 0.5) 1.0 kg (NW + 1.0) or 1.5 kg (NW + 1.5) at a speed of 2 m s(-1). Heart rate (HR), relative oxygen uptake ([Formula: see text]), blood lactate (La) and rate of perceived exertion (RPE) were registered along with surface EMG (SEMG) from biceps brachii, triceps brachii, trapecius and deltoideus muscles. Inbuilt force transducers measured reaction forces along the long axes of the poles. NW + 0.5 and NW + 1.5 showed significant increases for [Formula: see text] and RPE compared with W (p < 0.05) but with no respective differences within NW. SEMG revealed higher activation of biceps brachii for all NW tests plus added masses compared to W (p < 0.05). Additionally the activation of biceps brachii was higher for NW + 1.5 compared to NW (p < 0.05). The contribution to overall activation duration of triceps brachii became lower but increased for biceps brachii with heavier poles. The increased energy expenditure during NW can be attributed to intensified muscle activation during forward swing of the poles. Heavier poles have no effect on energy expenditure compared to NW with usual poles but enhance muscular activity. Since there are no benefits concerning physiological and biomechanical parameters we do not recommend the use of heavier NW poles. [ABSTRACT FROM AUTHOR]

Neural circuits responsible for stance control serve other motor tasks as well. We investigated the effect of prior locomotor tasks on stance, hypothesizing that postural post-effects of walking are dependent on walking direction. Subjects walked forward (WF) and backward (WB) on a treadmill. Prior to and after walking they maintained quiet stance. Ground reaction forces and centre of foot pressure (CoP), ankle and hip angles, and trunk inclination were measured during locomotion and stance. In WF compared to WB, joint angle changes were reversed, trunk was more flexed, and movement of CoP along the foot sole during the support phase of walking was opposite. During subsequent standing tasks, WB induced ankle extension, hip flexion, trunk backward leaning; WF induced ankle flexion and hip extension. The body CoP was displaced backward post-WB and forward post-WF. The post-effects are walking-direction dependent, and possibly related to foot-sole stimulation pattern and trunk inclination during walking. [ABSTRACT FROM AUTHOR]

The metabolic cost of walking ( C W) is increased in healthy older adults. Previously, this has been suggested to be associated with age-related decline in physiological/functional factors such as stability and muscle size and strength. Physical training can improve such factors as well as aspects of gait performance in older adults. The aim of this investigation was to determine if it also has a beneficial impact on (lowers) C W. Thirty-eight community dwelling older adults (aged 70–82 years) assigned to a training group (TRA, n=25) or a control group (CON, n=13) participated in a 12-month intervention. TRA followed a multi-component physical conditioning programme involving supervised resistance, aerobic, and balance exercises twice per week. They also undertook home based exercises once per week. CON carried on with their normal daily activities. C W and indicators of functional capacity (knee extensor isometric strength, single leg balance time, sit and reach, stand and reach, and 6 min walk distance) were assessed prior to and following the intervention. Significant improvements in knee extensor isometric strength (+21%), single leg balance time (+30%), and 6 min walk distance (+6%) were observed in TRA ( P<0.05) but not in CON. However, no change in C W was observed. In conclusion, this investigation has shown that a multi-component physical conditioning programme had a beneficial impact on functional capacity but did not lower C W in healthy community dwelling older adults. [ABSTRACT FROM AUTHOR]

A reply to comment on the paper "Energetics and mechanics of walking in patients with chronic low back pain and healthy matched controls," by Y. Henchoz et al., is presented. The paper authors point out that contrary to the interpretation of the International Physical Activity Questionnaire (IPAQ) results by the commentators, there was no substantial difference between the physical activity level of chronic low back pain (cLBP) and control (CTR) groups in the paper.