Cardiorespiratory responses to underwater treadmill walking in healthy females

This study compared the cardiorespiratory responses of eight healthy women (mean age 30.25 years) to submaximal exercise on land (LTm) and water treadmills (WTm) in chest-deep water (Aquaciser). In addition, the effects of two different water temperatures were examined (28 and 36°C). Each exercise test consisted of three consecutive 5-min bouts at 3.5, 4.5 and 5.5 km · h⁻¹. Oxygen consumption (V˙O₂) and heart rate (HR), measured using open-circuit spirometry and telemetry, respectively, increased linearly with increasing speed both in water and on land. At 3.5 km · h⁻¹ V˙O₂ was similar across procedures [χ = 0.6 (0.05) l · min⁻¹]. At 4.5 and 5.5 km · h⁻¹ V˙O₂ was significantly higher in water than on land, but there was no temperature effect (WTm: 0.9 and 1.4, respectively; LTm: 0.8 and 0.9 l · min⁻¹, respectively). HR was significantly higher in WTm at 36°C compared to WTm at 28°C at all speeds, and compared to LTm at 4.5 and 5.5 km · h⁻¹ (P ≤ 0.003). The HR-V˙O₂ relationship showed that at a V˙O₂ of 0.9 l · min⁻¹, HR was higher in water at 36°C (115 beats · min⁻¹) than either on land (100 beats · min⁻¹) or in water at 28°C (99 beats · min⁻¹). The Borg scale of perceived exertion showed that walking in water at 4.5 and 5.5 km · h⁻¹ was significantly harder than on land (WTm: 11.4 and 14, respectively; LTm: 9.9 and 11, respectively; P ≤ 0.001). These cardiorespiratory changes occurred despite a slower cadence in water (the mean difference at all speeds was 27 steps/min). Thus, walking in chest-deep water yields higher energy costs than walking at similar speeds on land. This data has implications for therapists working in hydrotherapy pools. Accepted: 3 September 1997     

Physiological responses to prolonged treadmill walking with external loads

Limited information is available regarding the physiological responses to prolonged load carriage. This study determined the energy cost of prolonged treadmill walking (fixed distance of 12 km) at speeds of 1.10 m.s-1, 1.35 m.s-1, and 1.60 m.s-1, unloaded (clothing mass 5.2 kg) and with external loads of 31.5 and 49.4 kg. Fifteen male subjects performed nine trials in random order over a 6-week period. Oxygen uptake (VO2) was determined at the end of the first 10 min and every 20 min thereafter. A 10-min rest period was allowed following each 50 min of walking. No changes occurred in VO2 over time in the unloaded condition at any speed. The 31.5 and 49.4 kg loads, however, produced significant increases (ranging from 10 to 18%) at the two fastest and at all three speeds, respectively, even at initial exercise intensities less than 30% VO2max. In addition, the 49.4 kg load elicited a significantly higher (P less than 0.05) VO2 than did the 31.5 kg load at all speeds. The measured values of metabolic cost were also compared to those predicted using the formula of Pandolf et al. In trials where VO2 increased significantly over time, predicted values underestimated the actual metabolic cost during the final minute by 10-16%. It is concluded that energy cost during prolonged load carriage is not constant but increases significantly over time even at low relative exercise intensities. It is further concluded that applying the prediction model which estimates energy expenditure from short-term load carriage efforts to prolonged load carriage can result in significant underestimations of the actual energy cost.     

The physiological effects of caffeine in women during treadmill walking

Although the effects of caffeine ingestion on athletic performance in men have been studied extensively, there is limited previous research examining caffeine's effects on women of average fitness levels participating in common modes of physical activity. The purpose of this study was to determine the effect of 2 levels of caffeine dosage on the metabolic and cardiorespiratory responses to treadmill walking in women. Subjects were 20 women (19-28 years of age) of average fitness, not habituated to caffeine. Each subject was assigned randomly a 3-mg x kg(-1) dose of caffeine, 6-mg x kg(-1) dose of caffeine, and placebo for 3 trials of moderate steady-state treadmill walking at 94 m x min(-1) (3.5 mph). Steady-state rating of perceived exertion (RPE), heart rate (HR), respiratory exchange ratio (RER), weight-relative VO2, %VO2max reserve (%VO2R), and rate of energy expenditure (REE) were measured during each trial. Repeated measures analysis of variance revealed that a 6-mg x kg(-1), but not a 3-mg x kg(-1) dose of caffeine increased VO2 (p = 0.04), REE (p = 0.03), and %VO2R (p = 0.03), when compared to the placebo. Caffeine had no effect on RPE, HR, or RER. No significant differences were observed between the placebo trials and the 3-mg x kg(-1) dose trials. Although a 6-mg x kg(-1) dose of caffeine significantly increased REE during exercise, the observed increase (approximately 0.23 kcal x min(-1)) would not noticeably affect weight loss. Because caffeine had no effect on RPE, it would not be prudent for a trainer to recommend caffeine in order to increase a woman's energy expenditure or to decrease perception of effort during mild exercise. These data also demonstrate that caffeine intake should not interfere with monitoring walking intensity by tracking exercise heart rate in women.     

Physiological responses to water-walking in middle aged women

The purpose of the present study was to examine the physiological responses to water-walking using the Flowmill, which has a treadmill at the base of a water-flume, in two groups of women. In the first group, the women were known to regularly swim and exercise in water (group A), while in the second, they did not routinely participate in water-exercise (group B). In both groups, twelve healthy female volunteers in their fifties participated in the study. All of the subjects walked in water using the Flowmill for the first time. Subjects completed four consecutive bouts of 4-minute duration at progressively increasing speeds (20, 30, 40, and 50 m.min-1), with 1-minute rests between each bout. In addition, water-velocity was adjusted to the walking speed of each bout. The water-depth of the Flowmill was the level of the xiphoid process. The water and room temperatures were 30.3 +/- 0.1 degrees C and 24.9 +/- 0.4 degrees C, respectively. In both groups, the relationship between walking speed and oxygen uptake (VO2) as well as that between walking speed and heart rate (HR) changed exponentially as the walking speed increased, and the relationship between HR and VO2 was linear. The relationship between HR and VO2 was similar in both groups, and there was no significant difference between the predicted maximal oxygen uptake (VO2max) of the two groups. VO2 and HR of group B during water-walking, however, were significantly higher than those of group A at all walking speeds. The results of this study clearly showed that experience in moving through the water strongly affects physiological responses to water-exercise, even when fitness levels are equivalent.     

Energy exchange between subject and belt during treadmill walking

Treadmill walking aims to simulate overground walking, but intra-stride belt speed variations of treadmills result in some interaction between treadmill and subject, possibly obstructing this aim. Especially in self-paced treadmill walking, in which the belt speed constantly adjusts to the subject, these interactions might affect the gait pattern significantly. The aim of this study was to quantify the energy exchange between subject and treadmill, during the fixed speed (FS) and self-paced (SP) modes of treadmill walking. Eighteen subjects walked on a dual-belt instrumented treadmill at both modes. The energy exchange was calculated as the integration of the product of the belt speed deviation and the fore-aft ground reaction force over the stride cycle. The total positive energy exchange was 0.44 J/stride and the negative exchange was 0.11 J/stride, which was both less than 1.6% of the performed work on the center of mass. Energy was mainly exchanged from subject to treadmill during both the braking and propulsive phase of gait. The two treadmill modes showed a similar pattern of energy exchange, with a slightly increased energy exchange during the braking phase of SP walking. It is concluded that treadmill walking is only mildly disturbed by subject-belt interactions when using instrumented treadmills with adequate belt control.     

Variability of ground reaction forces during treadmill walking.

The purpose of this study was to investigate whether or not the neuromuscular locomotor system is optimized at a unique speed by examining the variability of the ground reaction force (GRF) pattern during walking in relation to different constant speeds. Ten healthy male subjects were required to walk on a treadmill at 3.0, 4.0, 5.0, 6.0, 7.0, and 8.0 km/h. Three components [vertical (F(z)), anteroposterior (F(y)), and mediolateral (F(x)) force] of the GRF were independently measured for approximately 35 steps consecutively for each leg. To quantify the GRF pattern, five indexes (first and second peaks of F(z), first and second peaks of F(y), and F(x) peak) were defined. Coefficients of variation were calculated for these five indexes to evaluate the GRF variability for each walking speed. It became clear for first and second peaks of F(z) and F(x) peak that index variabilities increased in relation to increments in walking speed, whereas there was a speed (5.5-5.8 km/h) at which variability was minimum for first and second peaks of F(y), which were related to forward propulsion of the body. These results suggest that there is "an optimum speed" for the neuromuscular locomotor system but only for the propulsion control mechanism.     

Anthropology and style of life in middle age women

The anthropometric pattern, demographics data, lifestyle factors and several aspects of morbidity were analyzed for 400 Cuban women ages 40-60 years. More than 85% of women were obese, being these in direct association with morphology typically androgens, more evident in the postmenopausal women. In these women observed less body mass index and overweight, in an equivalent way between pre and postmenopausal women. A moderate consumption of rice, was evidenced, pastas and vegetables, few candies and fatty, what points to or quite acceptable knowledge of the harmful effect of some foods, to weigh that the shadowy use of saturated fats and not saturated it was the most frequent thing. By multifactor approach it is possible to make relation between nutritional patterns, morphology and climacteric symptoms; Cuban women present a different frequencies from an other literature showing the risk of generalist this studies and health's actions.     

IMU-based ambulatory walking speed estimation in constrained treadmill and overground walking

This study evaluated the performance of a walking speed estimation system based on using an inertial measurement unit (IMU), a combination of accelerometers and gyroscopes. The walking speed estimation algorithm segments the walking sequence into individual stride cycles (two steps) based on the inverted pendulum-like behaviour of the stance leg during walking and it integrates the angular velocity and linear accelerations of the shank to determine the displacement of each stride. The evaluation was performed in both treadmill and overground walking experiments with various constraints on walking speed, step length and step frequency to provide a relatively comprehensive assessment of the system. Promising results were obtained in providing accurate and consistent walking speed/step length estimation in different walking conditions. An overall percentage root mean squared error (%RMSE) of 4.2 and 4.0% was achieved in treadmill and overground walking experiments, respectively. With an increasing interest in understanding human walking biomechanics, the IMU-based ambulatory system could provide a useful walking speed/step length measurement/control tool for constrained walking studies.     

IMU-based ambulatory walking speed estimation in constrained treadmill and overground walking

This study evaluated the performance of a walking speed estimation system based on using an inertial measurement unit (IMU), a combination of accelerometers and gyroscopes. The walking speed estimation algorithm segments the walking sequence into individual stride cycles (two steps) based on the inverted pendulum-like behaviour of the stance leg during walking and it integrates the angular velocity and linear accelerations of the shank to determine the displacement of each stride. The evaluation was performed in both treadmill and overground walking experiments with various constraints on walking speed, step length and step frequency to provide a relatively comprehensive assessment of the system. Promising results were obtained in providing accurate and consistent walking speed/step length estimation in different walking conditions. An overall percentage root mean squared error (%RMSE) of 4.2 and 4.0% was achieved in treadmill and overground walking experiments, respectively. With an increasing interest in understanding human walking biomechanics, the IMU-based ambulatory system could provide a useful walking speed/step length measurement/control tool for constrained walking studies.     

Sex difference in the pattern of lower limb movement during treadmill walking

To evaluate the characteristics of stereo-typed movement of the lower limb during treadmill walking, the step length and duration of 200 steps were monitored consecutively and calculated by means of a computerized system, consisting of a position sensor, shoes with foot switches and a minicomputer. Eleven male and 10 female subjects walked at various constant speeds ranging from 60-130 m.min-1. Mean, standard deviation (SD) and coefficient of variation (CV) of the time-distance component at each speed were utilized for the assessment of stereotyped movement. When compared with males, females had a tendency to increase their speed by increasing their cadence. The difference of the walking pattern was specifically related to their height. The SD and CV of the time-distance component at a given speed were significantly greater in females than in males. Regression analyses revealed that in the relationship between the walking speeds and the SDs or CVs of the time-distance component, the significant quadratic equations could be fitted. The speed, at which the SD of step length was minimum, was estimated to be about 90 m.min-1 in both males and females. This was regarded as the free walking speed or as the walking speed resulting from a mechanically efficient step length which suited the subject's body size.     

Maximal oxygen uptake during treadmill walking and running at various speeds.

Three groups of male subjects, average fitness (AF, N = 12), high fitness (HF, N = 7) and highly fit competitive race walkers (CRW, N = 3) performed maximal treadmill tests walking at 3.5 and 4.5 mph and running at 4.5, 5.5, 7.0, and 8.5 mph. In addition, the HF group performed a running test at 10.0 mph and the CRW group performed a walking test at 5.5 mph. All maximal oxygen uptake (VO2 max) tests with the exception of the 3.5 mph walking test (modified Balke test) were discontinuous in nature. VO2 max obtained from walking tests was similar regardless of speed within each group. Walking VO2 max was significantly lower than running VO2 max which was found to be similar over a speed range of 4.5 to 8.5 mph in the AF group. Running at 4.5 mph (HF group) and 4.5 and 5.5 mph (CRW group) resulted in lower VO2 max levels than running at speeds greater than or equal to 7.0 mph. Associated physiological variables (heart rate, ventilation, and respiratory exchange ratio) did not demonstrate a discernable pattern with reference to mode of locomotion (walking versus running) or speed. It was concluded that VO2 max elicited during walking is independent of speed and less than VO2 max obtained during running. Running VO2 max was interrelated with speed of running and state of training.     

Physiological responses during meditation and rest

Forty nonmeditators and 12 experienced transcendental meditators were randomly assigned to four experimental cells devised to control for order and expectation effects. All 52 (female) subjects were continuously monitored on seven physiological measures during both meditation and rest. Each subject was her own control in an abab experimental paradigm comparing meditation to rest. Analyses of variance on change scores calculated from both initial and running (intertrial) baselines revealed small but significant conditions effects for all variables except diastolic BP. The same subjects (both experienced meditators and those meditating for the first time) showed lower psychophysiological arousal during the meditation than during the rest condition for systolic BP, HR, SCL, digital BV, digital ST, and frontalis EMG. The experienced meditators showed only marginally more conditions effects than the novices practicing noncultic meditation. For the nonmeditators, deliberately fostering positive expectations of meditations was associated with lower physiological arousal in terms of diastolic BP, HR, and SCL. These findings suggest that both cultic and noncultic meditation are associated with lower physiological activation than eyes-closed rest. The meditators, however, tended to become more relaxed over meditation trials, whereas the nonmeditators showed the opposite trend.     

Plasma FFA responses to prolonged walking in untrained men and women

Gender differences in plasma FFA responses to 90 min of treadmill walking at 35% VO2max were investigated in six men and six women following an overnight fast. The subjects represented average values for maximal oxygen uptake and body fat percentage for age and gender. Mean plasma FFA concentration at 45 and 90 min of exercise were significantly (P less than 0.05) higher for women (0.82 mmol X 1(-1), 0.88 mmol X 1(-1)) than men (0.42 mmol X 1(-1), 0.59 mmol X 1(-1)). Lower R values for women throughout the exercise period indicated a greater percentage fat in total metabolism than for men while the FFA/glycerol results supported greater lipolytic activity for women. The uniformity of percent fat in metabolism for women from rest to exercise showed that FFA release from adipose tissue increased rapidly with the onset of exercise which was not the case for men. Comparison of metabolic data as well as a statistical analysis (ANCOVA) controlling for the influence of VO2max and percentage body fat on FFA plasma concentration suggested that gender differences in FFA responses to prolonged submaximal exercise can be expected to occur in untrained subjects.     

Determining the centre of pressure during walking and running using an instrumented treadmill

In this paper, a new method of determining spatial and temporal gait parameters by using centre of pressure (CoP) data is presented. A treadmill is used which was developed to overcome limitations of regular methods for the analysis of spatio-temporal gait parameters and ground reaction forces during walking and running. The design of the treadmill is based on the use of force transducers underneath a separate left and right plate, which together form the treadmill walking surface. The results of test procedures and measurements show that accurate recordings of vertical ground reaction force can be obtained. These recordings enable a separate analysis of vertical ground reaction forces during double support phases in walking, and the analysis of changes in the centre of pressure (CoP) position during subsequent foot placements. From the CoP data, temporal gait parameters (e.g. duration of left/right support and swing phases) and spatial gait parameters (i.e. left/right step lengths and widths) can be derived.