Metabolic responses to submaximal treadmill walking and cycle ergometer pedalling in obese adolescents

Physical activity is essential in obesity management because of the impact of exercise‐related energy expenditure (EE) and fat oxidation (Fox) rate on a daily balance, but the specific physiological effects of different exercise modalities are scarcely known in obese individuals. The objective of the study was to compare the metabolic responses to treadmill (TM) and cycle ergometer (CE) exercise in obese adolescents. Gas exchange, heart rate (HR), blood lactate (LA) concentration, EE and Fox were determined at different intensity levels (up to about 85% of maximal oxygen uptake) during TM and CE in 14 pubertal (Tanner stage: >3) obese (BMI SDS: 2.15–3.86) male adolescents (age: 13–18 years). At comparable HR, oxygen uptake, EE and Fox were higher, and LA lower, during TM than CE (P<0.05–0.001), suggesting that cycling imposes a metabolic involvement at the level of the single active muscles greater than walking. Therefore, due to different physiological responses to TM and CE, walking was more convenient than cycling in obese adolescents, permitting to attain the same EE at lower HR, with lower blood LA concentration and with greater Fox. These conclusions seem clinically relevant when using exercise as a part of multidisciplinary treatment for juvenile obesity and amelioration of related metabolic disturbances.     

Physiological and perceptual responses to backward and forward treadmill walking in water

We compared physiological and perceptual responses, and stride characteristics while walking backward in water with those of walking forward in water. Eight males walked on an underwater treadmill, immersed to their xiphoid process level. Oxygen uptake ((.)V(O2)), respiratory exchange ratio (R), heart rate (HR), minute ventilation ((.)V(E)), blood lactate concentration (BLa), ratings of perceived exertion (RPE: for breathing and legs, RPE-Br and RPE-Legs, respectively), blood pressure (for systolic and diastolic pressures, SBP and DBP, respectively), and step frequency (SF) were measured. In addition, step length (SL) was calculated. (.)V(O2), R, HR, V (E), BLa, RPE-Br, RPE-Legs, and SBP were significantly higher while walking backward in water than when walking forward in water (P<0.05). Furthermore, SF was significantly higher (P<0.001) and SL was significantly lower (P<0.001) while walking backward in water, compared to walking forward in water. These results indicate that walking backward in water elicits higher physiological and perceptual responses than those produced when walking forward in water at the same speed.     

Metabolic responses to prolonged work during treadmill and water immersion running

The primary aim of this study was to compare the physiological responses to prolonged treadmill (TM) and water immersion to the neck (WI) running at threshold intensity. Ten endurance runners performed TM and WI running VO2max tests. Subjects completed submaximal performance tests at ventilatory threshold (Tvent) intensities under TM and WI conditions and responses at 15 and 42 minutes examined. VO2 was lower in WI (p<0.05) at maximal effort and Tvent. The Tvent VO2 intensities interpolated from the TM and WI VO2max tests were performed in both TM (i.e., TM@TM(tvent),TM@WI(tvent), corresponding to 77.6 and 71.3% respectively of TM VO2max) and WI conditions (i.e., WI@TM(tvent), WI@WI(tvent), corresponding to 85.5% and 78.2% respectively of WI VO2max). Each of the dependent variables was analyzed using a 3-way repeated measures ANOVA (2 conditions X 2 exercise intensities X 7 time points during exercise). VO2max values were significantly lower in the WI (52.4(5.1) ml.kg(-1) min(-1)) versus TM (59.7(6.5) ml.kg(-1) min(-1)) condition. VO2 during submaximal tests were similar during the TM and WI conditions. HR and [BLa] responses to exercise at and above WI(tvent) were similar during short-term exercise, but values tended to be lower during prolonged exercise in the WI condition. There were no statistical differences in VE responses in the 2 conditions, however as with HR and [BLa] an upward trend was noted with TM exercise over the 42 minute duration of the tests. RPE at WI(tvent) was similar for TM and WI exercise sessions, however, RPE at TM(tvent) was higher during WI compared to TM running. Cardiovascular drift was observed during prolonged TM but not WI running. Results suggest differences in metabolic responses to prolonged submaximal exercise in WI, however it can be used effectively for cross training.     

Metabolic accommodation of young children to treadmill walking

Few data exist concerning the reproducibility of stable oxygen uptake (VO(2)) values during level treadmill walking in young able-bodied children. To address this issue, 41 able-bodied 6-year-olds (19 boys, 22 girls, X height=117.2+/-4.7 cm, X body mass=21.8+/-2.5 kg) were tested on two occasions. In session 1, subjects were familiarized with the laboratory environment and performed 5 min of level treadmill walking at 1.34 m s(-1). During session 2, each child completed 30 min (three 10-min trials) of level treadmill walking at 1.34 m s(-1). For each 10-min trial, mean VO(2) was determined by averaging VO(2) values obtained from analysis of two 2-min expired gas samples. While the mean VO(2) for trial 1 was higher than values recorded for trials 2 and 3, effect sizes corresponding to these differences were low (相似文献   

Adaptive gait responses to awareness of an impending slip during treadmill walking

The awareness of potential slip risk has been shown to cause protective changes to human gait during overground walking. It remains unknown if such adaptations to walking pattern also exist when ambulating on a treadmill. This study sought to determine whether and to what extent individuals, when being aware of a potential slip risk during treadmill walking, could adjust their gait pattern to improve their dynamic stability against backward balance loss in response to the impending slip hazard. Fifty-four healthy young subjects (age: 23.9 ± 4.7 years) participated in this study. Subjects’ gait pattern was measured under two conditions: walking on a treadmill without (or normal walking) and with (or aware walking) the awareness of the potential slip perturbation. During both walking conditions, subjects’ full body kinematics were gathered by using a motion capture system. Spatial gait parameters and the dynamic gait stability against backward balance were compared between the two walking conditions. The results revealed that subjects proactively adopted a “cautious gait” during aware walking compared with the normal walking. The cautious gait, which was achieved by taking a shorter step and a more flatfoot landing, positioned the body center of mass closer to the base of support, improving participants’ dynamic stability and increasing their resistance against a possible slip-related fall. The finding from this study could provide insights into the dynamic stability control when individuals anticipate potential slip risk during treadmill walking.     

A comparison of muscle activity and heart rate response during backward and forward walking on an underwater treadmill

This investigation compared muscle activities and heart rate (HR) responses while subjects walked backward or forward in water, with and without a water current. Ten healthy males (23.5+/-1.4 years) volunteered for the study. Surface electromyography (EMG) was used to evaluate muscle activities while the subjects walked in water, immersed to the level of the xiphoid process. HR responses were monitored continuously by a telemetry method. A "Flowmill" was used for this study, which involves a treadmill at the base of a water flume. Measurement of maximal voluntary contraction (MVC) of each tested muscle was undertaken prior to gait analysis. The %MVCs obtained from the paraspinal muscles, vastus medialis and tibialis anterior were all significantly greater when walking backward than when walking forward, for every experimental condition (P<0.05). HR responses tended to be greater while walking backward than when walking forward, with a statistical significance at fast speed (P<0.05). In conclusion, walking backward in water resulted in significantly greater muscle activation of the paraspinal muscles, vastus medialis and tibialis anterior compared with walking forward in water. These findings may be helpful in developing water-based exercise programs.     

Metabolic cost and co-contraction during walking at different speeds in young and old adults

BackgroundThe net metabolic cost of walking (NCw) and the co-activation of leg muscles are both higher in old adults (OG) than in young adults (YG). Nevertheless, the relation between the two remains unresolved, mainly due to the controversial co-activation measurement method used in previous studies.Research questionTo compare ankle and knee co-contraction (CCI), calculated using an EMG-driven method, between the groups and to examine their relationship with NCw.MethodsNine young (YG = 25.2 +/- 3.3 years old) and nine older (OG = 68.7 +/5.9 years old) adults walked on a treadmill at five speeds (YG: 1; 1.2; 1.4; 1.6; 1.8 m/s; OG: 0.6; 0.8; 1; 1.2; 1.4 m/s) while electromyography (sEMG) and oxygen consumption were measured. CCI were calculated around the ankle and knee for different parts of the gait cycle (entire gait cycle 0–100 %, stance phase 0–60 %, swing phase 60–100 %).ResultsNCw was significantly higher (25 %, averaged over the walking speeds) in OG as were Knee_CCI, Knee_CCI_swing and Knee_CCI_stance. Multiple regression models in YG, OG and YG + OG highlighted Ankle_CCI as the main contributor in NCw (β = 0.08−0.188, p < 0.05) with a positive relation between the two variables.SignificanceThe present findings provide a better understanding of the association between muscle co-contraction and metabolic cost in older adults. It may help scientists and clinicians to further develop strategies aimed at neuromuscular rehabilitation as a means of improving mobility and independence among older adults.     

Ability of different physical activity monitors to detect movement during treadmill walking

This study assessed the ability of four different activity monitors to discriminate changes in treadmill walking velocity. The relationships between walking velocity and bodily movement and between bodily movement and energy expenditure determined by indirect calorimetry (IC-EE or METs) were determined. Twenty-eight subjects walked at 3.2, 4.0, 4.8, 5.6, and 6.4 km/h (0 % grade) for 30 min on separate occasions. The Tritrac-R3D (TT), Computer Science & Applications, Inc. (CSA), and Mini-Logger (ML) activity monitors that measure bodily acceleration in one or three planes, and a Yamax Digiwalker-500 (YX) that records footsteps, were secured at the waistline of each subject. CSA monitors were also worn at the wrist and ankle. Walking velocity and bodily movement were significantly related (r = 0.89 to 0.93) for TT, CSA, ML, and YX. Importantly, changing each walking velocity produced significant changes in bodily movement that was detected by each monitor. Bodily movement and IC-EE were significantly related for TT, CSA, ML, and YX (r = 0.47 to 0.94). Compared to IC-EE, and at all walking speeds, EE was significantly overestimated by the TT, and EE was significantly underestimated by the YX. These results indicate that the activity monitors can differentiate bodily movement associated with walking at slow speeds better than they can estimate energy expenditure associated with walking at slow speeds.     

Familiarisation to treadmill walking in unimpaired older people

We studied the amount of time required for treadmill familiarisation in older people and also whether familiarised treadmill walking could be generalised to overground walking. Sixteen healthy volunteers over 65 years of age walked on a level overground walkway and on a treadmill at the same speed for up to 15 min. A motion measurement system was used to measure the sagittal-plane kinematics of the knee and cadence during overground walking and after 0, 2, 4, 6, 8, 10, 12 and 14 min of treadmill walking. Older adults had not familiarised to the treadmill within 15 min as many participants continued to hold the treadmill's handrails and as reliability and absolute difference scores were still changing. Participants were most familiarised after 14 min on the treadmill. Furthermore, treadmill walking after 14 min was not closely related to overground walking in older adults, with measures on the treadmill only being able to predict knee angles during overground to within 8.0 degrees , or cadence to within 16.6 steps/min with 95% confidence. Treadmill walking in older adults after a single 15-min training session could not be generalised to overground walking.     

Validation of different stepping counters during treadmill and over ground walking

BackgroundCommercially available physical activity trackers are very popular in the general population and are increasingly common in clinical and research settings. The marketfor activity trackers are rapidly expanding, requiring them to be validated on an ongoing basis. Different approaches have been used for validating these devices. Studies using treadmills shows good step-counting accuracy although test performed in field tests settings are limited.Research questionDoes step-counting validity differ between a field test and a treadmill protocol for different types of activity trackers?MethodsThirty healthy subjects participated in this study, mean age was 28.2 (± 4.33) years, body mass 78.9 (± 12.9) kg, and height 178.5 (± 9.7) cm. A treadmill protocol with three different walking speeds (2, 3 and 4 km/h) and a 982 m field test was used. During the tests, participants’ feet were filmed using a waist-mounted camera. The number of steps were extracted from the video data and used for comparison with four different step counters: a) Polar M200; b) Polar A300; c) Dunlop pedometer; d) Samsung Galaxy S9 smartphone. Validity and agreement determined was determined with the use of Bland-Altman plot and Spearman’s correlation.ResultsValidity was higher for the field test compared to the 4 km/h treadmill test for all tested devices. The smartphone was the most accurate in terms of error, validity and agreement for both the treadmill and field test. All devices performed poorly for the 2 km/h treadmill test and only the smartphone performed well at 3 km/h.SignificanceThe results of this study show that step counting validity and error obtained during treadmill walking is not similar to a field test. Future validation studies of activity trackers should consider this when designing a protocol. The smartphone had the lowest mean bias during the field test.     

Metabolic and hormonal responses to long-distance swimming in cold water

The acute effects of long-distance swimming in cold water on selected hormonal and metabolic variables were evaluated on 22 long-distance swimmers (16 males and 6 females) during a 32-km swimming competition (La Traversée Internationale du Lac St-Jean). The water temperature was 18.5 degrees C and the mean performance times were 8 h and 32 min for men (M) and 9 h and 1 min for women (F). The blood samples were withdrawn in the fasting state during the week preceding the event and within 30 min after completion of the race. A positive correlation was obtained, for both groups, between percent body fat and rectal temperature measured at the end of the competition. After the competition, an increase in plasma epinephrine, norepinephrine, cortisol, thyroxine, free fatty acids, lactate, a decrease in glucose and insulin and no change in growth hormone, triiodothyronine, triglycerides, and cholesterol concentrations were observed in both groups. The increase in plasma thyroxine was more pronounced in the slower swimmers while the change in blood cortisol concentrations was higher in the subjects having the most acute decrease in body temperature. Male and female swimmers have a similar metabolic and hormonal response to a long-distance swimming competition in cold water.     

Cardiovascular and metabolic responses of trained and untrained middle-aged men to a graded treadmill walking test.

A treadmill walking test was developed in order to provide a suitable method of assessing the fitness levels of sedentary middle-aged men (mean age, 44.3 yrs) at submaximal intensity. The incremental stages of the test enabled subjects to terminate the workload whenever undue discomfort was experienced. The test procedure was used in a preliminary experiment to compare the cardiovascular and metabolic responses of trained and untrained middle-aged men to exercise. Heart rate responses to the test were significantly higher (p less than 0.01) in the untrained, compared with the trained, men as were the post-exercise blood lactic acid concentrations (p less than 0.01), Respiratory Exchange Ratios (p less than 0.01), Ventilatory Equivalents (p less than 0.05) and Rate of Perceived Exertion (p less than 0.01). However, there were no differences in the oxygen cost of walking between the two groups.     

Physiologic responses to maximal treadmill and deep water running in men and women.

Maximal physiologic responses to treadmill running and deep water running using a flotation device were compared in 12 trained men and 12 trained women. Although the men had significantly higher ventilation volumes, VO2max (liters of oxygen per minute and milliliters of oxygen per kilogram per minute), there were no significant differences in maximal heart rates or respiratory exchange ratios between the sexes. Significantly lower ventilation volumes, VO2max (LO2.min-1 and mlO2.kg-1.min-1), and heart rates were obtained in response to maximal water running compared to treadmill running, regardless of gender. Neither the men's nor women's maximal respiratory exchange ratios were significantly different between modes. The analysis of variance indicated that there were no significant interactions for any of the maximal responses to the tests between the sexes. The magnitude of these differences is similar to that found between treadmill running and cycling ergometry and should not preclude deep water running as a training technique. Caution, however, is advised if the training intensity is to be prescribed on the basis of land-determined heart rates.     

Cold-induced vasodilatation response at different water bath temperatures in monkeys.

The response of cold-induced vasodilatation (CIVD) at different water bath temperatures was studied in 20 monkeys (3.5 kg) in a conscious state in a thermoneutral room. The animals were controlled by seating in a monkey chair, and the right hind limb up to 7.5 cm from the heel was immersed in a water bath for 60 min. Four series of experiments were conducted at water bath temperatures of 0 degrees, 4 degrees, 8 degrees, and 12 degrees C, respectively, at weekly intervals and the skin temperatures were measured from three sites in the foot. Marked CIVD response was noted from the dorsum and, to a lesser extent, from the sole of the foot, but no response was seen from the tip of the middle toe at 0 degrees, 4 degrees, and 8 degrees C water bath temperatures. The pattern of CIVD response at 4 degrees C was identical to that of 0 degrees C, but the response at 8 degrees C was poor and was absent at 12 degrees C. Three patterns of CIVD--such as hunting, proportional control, and slow, steady, and continuous rewarming--was observed. However, 15% of the animals did not exhibit any CIVD. The observations show that the CIVD response of monkeys is remarkably similar to that of man.