Walking Bouts Research Articles

Age-related forgetting in locomotor adaptation

The healthy aging process affects the ability to learn and remember new facts and tasks. Prior work has shown that motor learning can be adversely affected by non-motor deficits, such as time. Here we investigated how age, and a dual task influence the learning and forgetting of a new walking pattern. We studied healthy younger (<30yo) and older adults (>50yo) as they alternated between 5-min bouts of split-belt treadmill walking and resting. Older subjects learned a new walking pattern at the same rate as younger subjects, but forgot some of the new pattern during the rest breaks. We tested if forgetting was due to reliance on a cognitive strategy that was not fully engaged after rest breaks. When older subjects performed a dual cognitive task to reduce strategic control of split-belt walking, their adaptation rate slowed, but they still forgot much of the new pattern during the rest breaks. Our results demonstrate that the healthy aging process is one component that weakens motor memories during rest breaks and that this phenomenon cannot be explained solely by reliance on a conscious strategy in older adults.

Individual blood pressure responses to walking and resistance exercise in peripheral artery disease patients: Are the mean values describing what is happening?

The aim of this study was to analyze the average and individual blood pressure responses to walking and resistance exercise in patients with peripheral artery disease. Thirteen patients underwent three experimental sessions: walking exercise, resistance exercise, and control. Ambulatory blood pressure, heart rate, and rate pressure product were obtained before and until 24 hours after sessions. The mean cardiovascular values during 24 hours, awake, and sleep periods were similar (P > 0.05) after the three experimental sessions. The analysis of individual data revealed that during 24 hours, eight of 13 patients reduced systolic or diastolic blood pressure in ≥4.0 mm Hg in at least one of the exercise session; furthermore, most of these patients presented greater responses after resistance exercise. The clinical characteristics of patients seem to influence the blood pressure responses after exercises. Individual data showed that part of patients presented clinically significant decreases in blood pressure, showing that these patients have acute cardiovascular benefits after performing an acute bout of exercise. Although, in average, a bout of walking or resistance exercise did not decrease ambulatory blood pressure in peripheral artery disease patients, the individual data revealed that most patients presented clinically relevant blood pressure reductions, especially after resistance exercise.

Abstract 15859: Interrupting Prolonged Sitting Reduces Resting Blood Pressure and Plasma Norepinephrine in Adults With Type 2 Diabetes

Interrupting prolonged sitting with frequent short bouts of light-intensity physical activity reduces blood pressure (BP) in overweight, non-diabetic adults, however, the effects in adults with type 2 diabetes (T2D) have not been investigated. This study examined the effects of two types of activity breaks (light-intensity walking or simple resistance activities) compared to continuous, uninterrupted sitting on resting BP and plasma norepinephrine (NE) in adults with T2D. In a randomized crossover trial, 24 inactive adults with T2D (14 male; 62 ± 6 y; BMI 33.0 ± 3.4 kg/m 2 ) consumed standardized breakfast and lunch meals during 3 x 8 h conditions (6-day washout): i) SIT: uninterrupted sitting (control); ii) LW: sitting + 3 min bouts of Light-intensity Walking (3.2 km/h every 30 min); and iii) SRA: sitting + 3 min bouts of Simple Resistance Activities (half-squats, calf raises, gluteal contractions and knee raises) every 30 min. Resting seated BP was measured hourly (mean of 3 recordings, performed ≥ 25 min after activity). Venous blood was drawn every 30 min for the plasma NE assay, ≥ 25 min after activity. As illustrated in figures 1A and 1B, compared to SIT, both LW and SRA reduced BP ( P &lt; 0.001); with the effect being more pronounced with SRA ( P &lt; 0.01 vs. LW). Similarly, compared to SIT, both LW and SRA reduced plasma NE concentrations, with SRA significantly lower than LW ( P &lt; 0.01). In conclusion, simple interruptions to sitting lowered resting BP and plasma NE concentration in adults with T2D. Reduced sympathetic vasoconstrictor tone may contribute to the observed hypotensive effect. With the ubiquity of sedentary behaviours and the low adherence to structured exercise, this approach is a practical strategy which may contribute to BP control.

Improved Walking Claudication Distance with Transcutaneous Electrical Nerve Stimulation: An Old Treatment with a New Indication in Patients with Peripheral Artery Disease.

The aim of this study was to determine whether 45 mins of transcutaneous electrical nerve stimulation before exercise could delay pain onset and increase walking distance in peripheral artery disease patients. After a baseline assessment of the walking velocity that led to pain after 300 m, 15 peripheral artery disease patients underwent four exercise sessions in a random order. The patients had a 45-min transcutaneous electrical nerve stimulation session with different experimental conditions: 80 Hz, 10 Hz, sham (presence of electrodes without stimulation), or control with no electrodes, immediately followed by five walking bouts on a treadmill until pain occurred. The patients were allowed to rest for 10 mins between each bout and had no feedback concerning the walking distance achieved. Total walking distance was significantly different between T10, T80, sham, and control (P < 0.0003). No difference was observed between T10 and T80, but T10 was different from sham and control. Sham, T10, and T80 were all different from control (P < 0.001). There was no difference between each condition for heart rate and blood pressure. Transcutaneous electrical nerve stimulation immediately before walking can delay pain onset and increase walking distance in patients with class II peripheral artery disease, with transcutaneous electrical nerve stimulation of 10 Hz being the most effective.

A Single Bout of Moderate Aerobic Exercise Improves Motor Skill Acquisition.

Long-term exercise is associated with improved performance on a variety of cognitive tasks including attention, executive function, and long-term memory. Remarkably, recent studies have shown that even a single bout of aerobic exercise can lead to immediate improvements in declarative learning and memory, but less is known about the effect of exercise on motor learning. Here we sought to determine the effect of a single bout of moderate intensity aerobic exercise on motor skill learning. In experiment 1, we investigated the effect of moderate aerobic exercise on motor acquisition. 24 young, healthy adults performed a motor learning task either immediately after 30 minutes of moderate intensity running, after running followed by a long rest period, or after slow walking. Motor skill was assessed via a speed-accuracy tradeoff function to determine how exercise might differentially affect two distinct components of motor learning performance: movement speed and accuracy. In experiment 2, we investigated both acquisition and retention of motor skill across multiple days of training. 20 additional participants performed either a bout of running or slow walking immediately before motor learning on three consecutive days, and only motor learning (no exercise) on a fourth day. We found that moderate intensity running led to an immediate improvement in motor acquisition for both a single session and on multiple sessions across subsequent days, but had no effect on between-day retention. This effect was driven by improved movement accuracy, as opposed to speed. However, the benefit of exercise was dependent upon motor learning occurring immediately after exercise–resting for a period of one hour after exercise diminished the effect. These results demonstrate that moderate intensity exercise can prime the nervous system for the acquisition of new motor skills, and suggest that similar exercise protocols may be effective in improving the outcomes of movement rehabilitation programs.

Test-retest Reliability of GPS derived Measurements in Patients with Claudication

In patients with peripheral artery disease (PAD), the different distances between stops and the stop durations recorded with Global Positioning System (GPS) during a 1 hour stroll in the community are highly variable. Nevertheless, the reliability of the greatest community walk distance (greatest distance), the average of walking speeds (average speed) and the durations of stops (average stop durations) have not been studied. Seventeen PAD patients performed two series of evaluations (T1 and T2) within a 1 month period. Each series included: a 1 hour stroll in the community with the calculation of the walking impairment questionnaire (WIQ) scores, the measurement of maximal walking distance on a treadmill (MWD on treadmill) and a 1 hour stroll in the community with GPS. The Garmin GPS-60 (Garmin Ltd, Olathe, Kan) receiver was used for all patients. Test-retest reliability of MWD on treadmill, WIQ, and GPS parameters were assessed with intraclass coefficient of correlation (ICC). ICCs are almost perfect between T1 and T2 for greatest distance (ICC=0.911), average speed (ICC=0.905), and MWD on treadmill (ICC=0.992), and substantial for the average WIQ (ICC=0.794). Correlation of average stop durations was considered substantial (ICC=0.691). Despite the previously reported "within stroll" variability of walking bouts for distances, speeds, and stop durations, GPS derived greatest distance and average speed are reliable in PAD patients in test-retest experiments. The GPS appears to be a new tool to assess walking limitation and allows objective clinical investigation.

Effects of Interrupting Children's Sedentary Behaviors With Activity on Metabolic Function: A Randomized Trial.

Limited data suggest that interrupting sedentary behaviors with activity improves metabolic parameters in adults. We tested whether interrupting sitting with short, moderate-intensity walking bouts improved glucose tolerance in children. Participants underwent two experimental conditions in random order on different days: continuous sitting for 3 hours or sitting interrupted by walking (3 min of moderate-intensity walking every 30 min). Insulin, C-peptide, glucose, and free fatty acids were measured every 30 minutes for 3 hours during an oral glucose tolerance test. Area under the curve (AUC) was calculated from hormone and substrate measurements. Children were given a buffet meal after each condition. The study was conducted at the National Institutes of Health Hatfield Clinical Research Center. Twenty-eight normal-weight 7-11 year olds participated. Patterns of substrate/hormone secretion and AUC, as well as energy intake, were examined by experimental condition. Interrupting sitting resulted in a 32% lower insulin AUC (P < .001), 17% lower C-peptide AUC (P < .001), and 7% lower glucose AUC (P = .018) vs continuous sitting. Mixed model results indicated that insulin (P = .036) and free fatty acid concentrations (P = .009) were significantly lower in the interrupted vs the continuous sitting condition. Lunchtime buffet meal energy intake did not significantly differ between the conditions (975 ± 387 vs 963 ± 309 kcal; P = .85). Interrupting sedentary time with brief moderate-intensity walking improved short-term metabolic function in non-overweight children without increasing subsequent energy intake. These findings suggest that interrupting sedentary behavior may be a promising prevention strategy for reducing cardiometabolic risk in children.

Exercise training modifies walking kinematics and energy cost in obese adolescents: A pilot controlled trial

The aim of this study was to investigate the effects of a weight loss intervention based on physical exercise on the relationship between energy cost and stride frequency during walking in obese teenagers. Participants aged 13–16 years old were assigned to a training (n = 14) and control (n = 10) groups. During eight weeks, the training group performed three 60-min weekly sessions of high-intensity intermittent activities coupled with aerobic training. Body composition, gait parameters and energy cost during 4-min walking bouts at participants’ most comfortable speed and preferred stride frequency (PSF), PSF-10%, PSF + 10%, PSF-20% and PSF + 20% were measured before and after intervention. The effects of training and stride frequencies on the energy cost of walking were analysed by an ANOVA with repeated measures. The main results showed that the exercise intervention induced a significant increase in walking speed (+23.2%), and significant decreases in body mass (−1.4%), body fat percentage (−2.1%) and energy cost of walking at various frequencies (decreases ranging from −10.5% to −20.4%, p < .05). In addition, significantly greater decreases were shown at high frequencies (p < .05). No significant differences were shown in the control group (p > .05). These results suggest that this type of training is beneficial to reduce walking energy cost of obese teenagers, in particular at high frequencies. This should improve their well-being during daily activities.

Impact of leg blood flow restriction during walking on central arterial hemodynamics.

Walking exercise with limb blood flow restriction (BFR) has been shown to increase muscular mass and strength even if it is performed at low exercise intensities. Despite mounting evidence for its efficacy and the increasing popularity, the safety of BFR exercise in relation to cardiac loads has not been established. The aim of this study was to determine the response of central hemodynamics during the BFR exercise to assess its impact on cardiac load. Fifteen apparently healthy sedentary or recreationally active adults (10 men and 5 women, 27 ± 1 yr) underwent five bouts of 2-min constant treadmill walking at 2 mph with 1-min rest intervals either with or without BFR on both proximal thighs. Beat-by-beat blood pressure and hemodynamics (via Modelflow method) were measured, and central arterial hemodynamics were evaluated with pulse wave analyses via general transfer function. Incident wave amplitude (IWA) and reflected wave amplitude (RWA) were obtained by the wave separation analysis. Peripheral systolic blood pressure (SBP) increased more substantially during walking with BFR (43 ± 5% vs. baseline) than without BFR (11 ± 4% vs. baseline). Aortic SBP did not change significantly during walking without BFR, but there was a substantial elevation in aortic SBP (43 ± 5% vs. baseline) during walking with BFR. Significant effect of BFR was seen in IWA but not in RWA. These findings suggest that even during slow-speed walking, leg BFR induces substantial hypertensive responses in the aorta. However, this response could not be explained by the augmented wave reflection.

Accelerometer-based Physical Activity Monitoring in Patients with Knee Osteoarthritis: Objective and Ambulatory Assessment of Actual Physical Activity During Daily Life Circumstances.

Background: It is important to assess physical activity objectively during daily life circumstances, to understand the association between physical activity and diseases and to determine the effectiveness of interventions. Accelerometer-based physical activity monitoring seems a promising method and could potentially capture all four FITT (i.e. Frequency, Intensity, Time, Type) components of physical activity considered by the World Health Organization (WHO).Aim: To assess the four FITT components of physical activity with an accelerometer during daily life circumstances and compare with self-reported levels of physical activity in patients with knee osteoarthritis (OA) and a healthy control group.Methods: Patients (n=30) with end-stage knee OA and age-matched healthy subjects (n=30) were measured. An ambulant tri-axial accelerometer was placed onto the lateral side of the upper leg. Physical activity was measured during four consecutive days. Using algorithm-based peak detection methods in Matlab, parameters covering the four FITT components were assessed. Self-reported physical activity was assessed using the Short questionnaire to assess health enhancing physical activity (SQUASH).Results: Knee OA patients demonstrated fewer walking bouts (154 ±79 versus 215 ±65 resp.; p=0.002), step counts (4402 ±2960 steps/day versus 6943 ±2581 steps/day; p=0.001) and sit-to-stand (STS) transfers (37 ±14 versus 44 ±12; p=0.031) compared to controls. Knee OA patients demonstrated more time sitting (65 ±15% versus 57 ±10% resp.; p=0.029), less time walking (8 ±4% versus 11 ±4% resp.; p=0.014) and lower walking cadence (87 ±11steps/min versus 99 ± 8steps/min resp.; p<0.001). Accelerometer-based parameters of physical activity were moderately-strong (Pearsons’s r= 0.28-0.49) correlated to self-reported SQUASH scores.Conclusion: A single ambulant accelerometer-based physical activity monitor feasibly captures the four FITT components of physical activity and provides more insight into the actual physical activity behavior and limitations of knee OA patients in their daily life.

Development and validation of a novel pedometer algorithm to quantify extended characteristics of the locomotor behavior of dairy cows

Behavior is one of the most important indicators for assessing cattle health and well-being. The objective of this study was to develop and validate a novel algorithm to monitor locomotor behavior of loose-housed dairy cows based on the output of the RumiWatch pedometer (ITIN+HOCH GmbH, Fütterungstechnik, Liestal, Switzerland). Data of locomotion were acquired by simultaneous pedometer measurements at a sampling rate of 10 Hz and video recordings for manual observation later. The study consisted of 3 independent experiments. Experiment 1 was carried out to develop and validate the algorithm for lying behavior, experiment 2 for walking and standing behavior, and experiment 3 for stride duration and stride length. The final version was validated, using the raw data, collected from cows not included in the development of the algorithm. Spearman correlation coefficients were calculated between accelerometer variables and respective data derived from the video recordings (gold standard). Dichotomous data were expressed as the proportion of correctly detected events, and the overall difference for continuous data was expressed as the relative measurement error. The proportions for correctly detected events or bouts were 1 for stand ups, lie downs, standing bouts, and lying bouts and 0.99 for walking bouts. The relative measurement error and Spearman correlation coefficient for lying time were 0.09% and 1; for standing time, 4.7% and 0.96; for walking time, 17.12% and 0.96; for number of strides, 6.23% and 0.98; for stride duration, 6.65% and 0.75; and for stride length, 11.92% and 0.81, respectively. The strong to very high correlations of the variables between visual observation and converted pedometer data indicate that the novel RumiWatch algorithm may markedly improve automated livestock management systems for efficient health monitoring of dairy cows.

Effects of Intermittent Versus Continuous Walking on Distance Walked and Fatigue in Persons With Multiple Sclerosis: A Randomized Crossover Trial.

Fatigue is a common, disabling symptom experienced by persons with multiple sclerosis (MS). Evidence shows that intermittent exercise is associated in improved performance and negligible fatigue. The purpose of this study was to examine whether subjects with MS walk greater distances with less fatigue under intermittent (INT) or continuous (CONT) walking condition. Twenty-seven subjects with MS (median Extended Disability Severity Scale 3.5, interquartile range 1.6) walked in the CONT (ie, 6 uninterrupted minutes) and INT (ie, three 2-minute walking bouts) conditions in a randomized crossover. Distance was measured for the entire 6-minute walking period and each 2-minute increment. Fatigue was measured as the difference in a visual analog scale of fatigue (ΔVAS-F) immediately preceding and following each trial. Participants walked greater distances in the INT condition compared to the CONT condition (P = 0.005). There was a significant interaction of walking condition and time (P < 0.001), indicating that the distances walked in the INT condition changed across time. ΔVAS-F was significantly lower in the INT condition than in the CONT condition (P = 0.036). Subjects with MS walked farther, and with less fatigue, when walking intermittently rather than continuously. Persons with MS may be able to tolerate a greater dose of walking training if the walking bouts are intermittent. Further study to determine the benefits of a walking exercise program using intermittent walking is recommended.Video Abstract available for additional insights from the authors (Supplemental Digital Content 1, http://links.lww.com/JNPT/A103).

A Physiological Perspective on Treadmill and Sit-to-Stand Workstations

Active workstations, such as treadmill and sit-to-stand workstations, enable office employees to break prolonged sitting with bouts of light-intensity walking and/or standing. Compared with sitting, walking and/or standing accumulated during the workday using these workstations will increase muscle contractions, which may influence blood flow, energy expenditure, metabolism, musculoskeletal health, and brain function. Physiological responses when using treadmill and sit-to-stand workstations may vary due to differences in muscle contraction type (dynamic vs. static) and may thus affect cardio-metabolic and musculoskeletal health and brain function in different ways.

Impact of prolonged sitting on lower and upper limb micro- and macrovascular dilator function.

What is the central question of this study? The prevalence of sedentary behaviour in the workplace and increased daily sitting time have been associated with the development of cardiovascular disease; however, studies investigating the impact of sitting on vascular function remain limited. What is the main finding and its importance? We demonstrate that there is a marked vulnerability of the vasculature in the lower and upper limbs to prolonged sitting and highlight the importance of physical activity in restoring vascular function in a limb-specific manner. Sedentary behaviour in the workplace and increased daily sitting time are on the rise; however, studies investigating the impact of sitting on vascular function remain limited. Herein, we hypothesized that 6 h of uninterrupted sitting would impair limb micro- and macrovascular dilator function and that this impairment could be improved with a bout of walking. Resting blood flow, reactive hyperaemia to 5 min cuff occlusion (microvascular reactivity) and associated flow-mediated dilatation (FMD; macrovascular reactivity) were assessed in popliteal and brachial arteries of young men at baseline (Pre Sit) and after 6 h of uninterrupted sitting (Post Sit). Measures were then repeated after a 10 min walk (~1000 steps). Sitting resulted in a marked reduction of resting popliteal artery mean blood flow and mean shear rate (6 h mean shear rate, -52 ± 8 s(-1) versus Pre Sit, P < 0.05). Interestingly, reductions were also found in the brachial artery (6 h mean shear rate, -169 ± 41 s(-1) versus Pre Sit, P < 0.05). Likewise, after 6 h of sitting, cuff-induced reactive hyperaemia was reduced in both the lower leg (-43 ± 7% versus Pre Sit, P < 0.05) and forearm (-31 ± 11% versus Pre Sit, P < 0.05). In contrast, popliteal but not brachial artery FMD was blunted with sitting. Notably, lower leg reactive hyperaemia and FMD were restored after walking. Collectively, these data suggest that prolonged sitting markedly reduces lower leg micro- and macrovascular dilator function, but these impairments can be fully normalized with a short bout of walking. In contrast, upper arm microvascular reactivity is selectively impaired with prolonged sitting, and walking does not influence this effect.

Use of Hourly Walking Breaks to Increase Daily Walking Among Inactive Office Workers

Prolonged periods of sitting can lead to increased health risks. Office workers are especially susceptible to bouts of prolonged sedentary time while at work. PURPOSE: To perform an 8-wk pilot study to examine the effects of 5-min walking breaks on physical activity (PA) levels among physically inactive office workers. METHODS: Fourteen office workers participated in the study (age, 54±5 yrs; body mass index, 36±5 kg.m−2). Eligible participants (age, 40–65 yrs; waist circumference, ≥88 cm (females) or 102 cm (males); <7,000 steps.day−1,) were randomized to either an experimental group (EXP, n=7) or control group (CON, n=7). The EXP was instructed to perform a 5-min walking break every hour during the workday for 8 wks and wore a FitBit Zip during all waking hours from baseline (PRE) to post-testing (POST) to track PA. A valid walking break was defined as a walking bout lasting 4 min or longer and accumulating at least 240 steps. Repeated measures 2x2 ANOVAs were used to assess change in outcome variables. RESULTS: From PRE to POST, the EXP significantly increased average number of daily walking bouts (PRE=2.4 vs. POST=4.1 bouts/d; p<0.05) and average daily steps (PRE=3457 vs. POST=4309 steps/d; p<0.05). There was a non-significant increase in walking bout duration, among the EXP (PRE=7.5 vs. POST=8.6 min/d) with no change among the CON (PRE=8.1 vs. POST=8.0 min/d; all p>0.05). Specific to working hours, non-significant increases were seen for the EXP in steps (PRE=2357 vs. POST=4309 steps/d), average number of walking bouts (PRE=1.7 vs. POST=3.3 bouts/d) and average duration of each walking bout (PRE=7.3 vs. POST=8.4 min/d; all p>0.05). Steps taken during the workday accounted for more than half of the total daily steps during both PRE (EXP=68% vs. CON=61%) and POST (EXP=74% vs. CON=62%). CONCLUSION: An hourly 5-min walking break prescription during the workday resulted in increased walking among the EXP. Extrapolating the bouts/d and min/bout the EXP nearly doubled their walking time from 18 min/d to 35 min/d, thus helping them meet the national PA recommendation. Future worksite wellness programs utilizing a similar PA prescription may be effective at increasing PA levels among sedentary office workers.

Cardiorespiratory and Metabolic Responses During Robotic Exoskeleton-Assisted Walking Among Persons with Chronic Spinal Cord Injury

PURPOSE: Robotic exoskeleton technology is being developed with the promise of affording people with lower limb paralysis the opportunity to stand and walk. The mobility benefits of robotic exoskeleton-assisted walking can be realized immediately, however the potential health and fitness benefits of this technology have yet to be investigated. The purpose of this study was to determine the cardiorespiratory and metabolic responses during robotic exoskeleton-assisted walking and compare these findings to current physical activity guidelines. METHODS: Four subjects with chronic spinal cord injury were recruited from a rehabilitation hospital. Expired gases were collected during maximal graded exercise testing (GXT) using an arm cycle ergometer and 6-minute walk tests performed at “self-selected” gait speed (Walk 1) and as “quickly but as safely as possible” (Walk 2). Subjects ambulated using a robotic exoskeleton and an assistive walking device of their choice. Primary outcome measures included oxygen consumption (VO2), metabolic equivalent of tasks (METs), walk speed and total walk distance. RESULTS: Statistically significant differences were observed (p<0.05) between Walk 1 and Walk 2 for walk speed (0.18±0.01m/sec vs. 0.27±0.06m/sec), total walk distance (66.41±3.15m vs. 98.25±20.91m), and VO2peak (10.9±1.0ml/kg/min vs. 13.3±1.2ml/kg/min) respectively. Compared to VO2peak (18.3±2.9ml/kg/min) as determined by GXT, %VO2peak during walking ranged from 60.8% (Walk 1) to 74.3% (Walk 2). METs were calculated relative to previously published data for SCI where 1MET=2.7ml/kg/min (Collins, E et al., 2010). Exoskeleton-assisted walking during Walk 1 and Walk 2 elicited a SCI MET equivalent range of 4.0±0.37 to 4.9±0.45 METs. CONCLUSION: Persons with lower limb paralysis may be limited in their capacity to perform physical exercise to the extent needed to improve health and fitness. Based on preliminary data, cardiorespiratory and metabolic demands of exoskeleton-assisted walking are consistent with physical activity performed at a moderate intensity (2008 PAG for Americans). Prolonged bouts of exoskeleton-assisted walking may provide the stimulus needed to improve cardiorespiratory fitness and possibly mitigate the onset of secondary health conditions. Future studies are needed to investigate the training effects of exoskeleton-assisted walking on cardiorespiratory fitness and overall health.

Comparing Energy Expenditure During Land and Shallow Water Walking in Overweight and Obese Women

Physical activity is an important behavior for overweight and obese individuals. Aquatic exercise, including shallow water walking, is a popular form of aerobic activity in this population not requiring swimming skill. Although it has been shown to provide metabolic, cardiovascular, and psychological benefits, few studies have compared the responses to this form of exercise to land-based exercise. PURPOSE: To compare the energy expenditure (kcal/min) of a bout of shallow water walking to bouts of land walking in overweight and obese women. METHODS: Nineteen women (42.11 ± 10.30 yrs; 30.91 ± 3.78 kg/m2) completed three 10-minute trials including: a 1) shallow water walking at a self-selected pace; 2) land walking matched (± 10bpm) to the HR response of the shallow water walking bout; and 3) land walking at a self-selected pace. Oxygen uptake (mL·kg-1·min-1), ventilation (L·min-1), and respiratory exchange ratio (RER) were collected using a portable metabolic unit adapted for use in water. RESULTS: Results showed no difference in energy expenditure between shallow water (6.46 ± 1.38 kcal/min) and land walking (6.92 ± 1.61 kcal/min) at self-selected paces. However, significantly lower energy expenditure (p= 0.046) was observed for shallow water walking compared to matched HR response land walking (7.26 ± 1.29 kcal/min). When the difference in relative energy expenditure (kcal/kg/min) between shallow water walking and the matched HR response land walking was correlated with BMI and percent body fat, a moderate relationship was shown (r= 0.551, p= 0.014; and r= 0.556, p= 0.013) suggesting that the difference was reduced at higher levels of BMI and percent body fat. There were no correlations observed between body composition and differences in energy expenditure between shallow water and land walking at a self-selected pace. CONCLUSIONS: Findings suggest that shallow water walking is a viable alternative to land walking and can elicit an increase in energy expenditure performed at a moderate intensity in overweight/obese women. Since the difference in shallow water vs. land-based energy expenditure was reduced at higher levels of BMI and percent body fat, future studies should examine whether there is a threshold of obesity or body fatness that alters the response to water exercise compared to land-based exercise.

Impact of Walking with Leg Blood Flow Restriction on Central Blood Pressure and Subendocardial Viability

PURPOSE: Walking exercise with limb blood flow restriction (BFR) has been shown to increase muscular mass and strength even if it is performed at low intensities. Despite mounting evidence for its efficacy and the increasing popularity, the safety of BFR exercise in relation to cardiac loads has not been established. We measured central blood pressure in order to more accurately assess blood pressure load imposed on the left ventricle during the BFR exercise. Additionally, as restricted venous return expectedly induced smaller increase in stroke volume and greater tachycardia (i.e., shorter diastolic duration), subendocardial viability ratio, an index of myocardial perfusion relative to left ventricular workload, was derived. METHODS: Fifteen apparently healthy adults (10 men and 5 women, 27±1 years) underwent five bouts of 2-minute treadmill walking at 2 miles/hour with 1-min interval either with or without BFR on both proximal thighs. Beat-by-beat peripheral blood pressure and hemodynamics were measured using the Portapres. Central arterial hemodynamics was evaluated with pulse wave analysis via general transfer function. RESULTS: Peripheral systolic blood pressure (SBP) increased during walking more substantially with BFR (43±5% vs. baseline) than without during BFR (12±4% vs. baseline). Although aortic SBP did not change significantly during walking without BFR, there was a substantial elevation in aortic SBP during walking with BFR (41±4% vs. baseline). Compared with the non-BFR session, significantly smaller increase in stroke volume and shorter diastolic duration were observed during the BFR session. Thus, despite greater hypertensive response, subendocardial viability ratio was significantly lower in the BFR session compared with the non-BFR session (P<0.05). CONCLUSIONS: These findings suggest that even during slow-speed walking, leg BFR induces a greater hypertensive response in the aorta and a lower myocardial perfusion. These central hemodynamic responses might force a circulatory challenge, particularly for those with compromised cardiovascular function.

Breaking up of prolonged sitting over three days sustains, but does not enhance, lowering of postprandial plasma glucose and insulin in overweight and obese adults.

To compare the cumulative (3-day) effect of prolonged sitting on metabolic responses during a mixed meal tolerance test (MTT), with sitting that is regularly interrupted with brief bouts of light-intensity walking. Overweight/obese adults (n=19) were recruited for a randomized, 3-day, outpatient, cross-over trial involving: (1) 7-h days of uninterrupted sitting (SIT); and (2) 7-h days of sitting with light-intensity activity breaks [BREAKS; 2-min of treadmill walking (3.2 km/h) every 20 min (total: 17 breaks/day)]. On days 1 and 3, participants underwent a MTT (75 g of carbohydrate, 50 g of fat) and the incremental area under the curve (iAUC) was calculated from hourly blood samples. Generalized estimating equation (GEE) models were adjusted for gender, body mass index (BMI), energy intake, treatment order and pre-prandial values to determine effects of time, condition and time × condition. The glucose iAUC was 1.3 ± 0.5 and 1.5 ± 0.5 mmol·h·l(-1) (mean differences ± S.E.M.) higher in SIT compared with BREAKS on days 1 and 3 respectively (condition effect: P=0.001), with no effect of time (P=0.48) or time × condition (P=0.8). The insulin iAUC was also higher on both days in SIT (day 1: ∆151 ± 73, day 3: ∆91 ± 73 pmol·h·l(-1), P=0.01), with no effect of time (P=0.52) or time × condition (P=0.71). There was no between-treatment difference in triglycerides (triacylglycerols) iAUC. There were significant between-condition effects but no temporal change in metabolic responses to MTT, indicating that breaking up of sitting over 3 days sustains, but does not enhance, the lowering of postprandial glucose and insulin.

An investigation into practical exercise strategies to offset the negative impact of 12h of sitting on glycaemic control

Recent evidence suggests that there is a dose‐response association between sitting time and mortality. It has been reported that breaking up sitting time improves glycaemic control. The AIM of this study was to compare 12h sitting (SIT) with two interventions to influence sedentary time – a bout of resistance exercise prior to 12h sitting (RE) and 6min walk/hour of 12h sitting (WALK).MethodsHealthy, active males took part in 3 trials. SIT: 12h sitting without any physical activity. RE: one bout of Resistance Exercise (4 x 10 reps; 75% 1RM) followed by 12h sitting. WALK: 12h sitting with bouts of walking (6min/hr; 40‐59% VO2max). Caloric intake remained similar between trials. The morning following each trial (12h post), blood samples collected at baseline and 15, 30, 45, 90 and 120 mins following an Oral Glucose Tolerance Test drink. Glucose and insulin measures [MATSUDA, HOMA‐IR, Area Under Curve (AUC)] were analysed.ResultsParticipants were young, fit individuals with VO2max of 57.4 ± 2.0 ml/kg/min and ~ 6 ± 0.8 hrs/week activity. Matsuda and HOMA‐IR were not significantly different between trials and participants remained in the healthy category for each even after 12h sitting. There were no significant differences in AUC for glucose (SIT: 150 ± 31, RE: 141 ± 28, WALK: 179 ± 29), but there was a trend for a reduction in AUC for insulin in WALK compared to SIT (SIT: 5346 ± 745, RE 4685 ± 809, WALK: 4308 ± 678; p&lt;0.09).ConclusionsOur results demonstrate that neither antecedent resistance exercise nor 6min/hr of brisk walking is sufficient to improve glucose tolerance in the face of 12 hrs of sitting. Further research is needed to optimise exercise strategies to offset the negative effects of prolonged sitting.