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Statin use and functional decline in patients with and without peripheral arterial disease.

OBJECTIVES: We determined whether statin use (vs. non-use) is associated with less annual decline in lower-extremity functioning in patients with and without lower-extremity peripheral arterial disease (PAD) over three-year follow-up. BACKGROUND: It is unclear whether statin use is associated with less functional decline in patients with PAD. METHODS: Participants included 332 men and women with an ankle brachial index (ABI) <0.90 and 212 with ABI 0.90 to 1.50. Functional outcomes included 6-min walk distance and usual and rapid-pace 4-m walking velocity. A summary performance score combined performance in walking speed, standing balance, and time for five repeated chair rises into an ordinal score ranging from 0 to 12 (12 = best). RESULTS: Adjusting for age, race, gender, comorbidities, education, health insurance, total cholesterol/high-density lipoprotein level, body mass index, pack-years of smoking, leg symptoms, immediately previous year functioning, statin use/non-use, ABI, and change in ABI, the PAD participants using statins had less annual decline in usual-pace walking velocity (0.002 vs. -0.024 m/s/year, p = 0.013), rapid-pace walking velocity (-0.006 vs. -0.042 m/s/year, p = 0.006), 6-min walk performance (-34.5 vs. -57.9 feet/year, p = 0.088), and the summary performance score (-0.152 vs. -0.376, p = 0.067) compared with non-users. These associations were attenuated slightly by additional adjustment for high-sensitivity C-reactive protein levels. Among non-PAD participants, there were no significant associations between statin use and functional decline. CONCLUSIONS: The PAD patients on statins have less annual decline in lower-extremity performance than PAD patients who are not taking statins.

Aged↗

Functional decline in lower-extremity peripheral arterial disease: associations with comorbidity, gender, and race.

PURPOSE: To identify comorbidities associated with increased rates of functional decline in persons with lower-extremity peripheral arterial disease (PAD). We also determined whether female sex and black race were associated with greater functional decline than male sex and white race, respectively, in PAD. METHODS: Three-hundred ninety-seven men and women with PAD were followed prospectively for a median of 36 months. The presence of comorbid illnesses was determined with medical record review, patient report, medications, laboratory values, and a primary care physician questionnaire. Functional outcomes, measured annually, included the 6-minute walk, usual-paced and fast-paced 4-meter walking speed, and summary performance score. The summary performance score is a composite measure of lower-extremity functioning (score range, 0 to 12; 12 = best). RESULTS: Adjusting for known and potential confounders, PAD patients with pulmonary disease had a significantly greater average annual decline in 6-minute walk performance of -34.02 ft/y (95% confidence interval [CI], -60.42 to -7.63; P = .012), rapid-paced 4-meter walk speed of -0.028 m/s/y (95% CI, -0.054 to -0.001; P = .042), and summary performance score of -0.460/y (95% CI, -0.762 to -0.157; P = .003) compared with those without pulmonary disease. PAD patients with spinal stenosis had a greater average annual decline in 6-minute walk performance of -77.4 ft/y (95% CI, -18.9 to -35.8; P < .001) and usual-paced 4-meter walking velocity of -0.045 m/s/y (95% CI, -0.081 to -0.009; P = .014) compared with participants without spinal stenosis. CONCLUSION: At 3-year follow-up, pulmonary disease and spinal stenosis were each associated with a significant decline in functioning among persons with PAD. In contrast, female sex and black race were not associated with functional decline among persons with PAD.

Aged↗

Body composition in the elderly: the influence of nutritional factors and physical activity.

BACKGROUND: Controversy exists regarding the relative contribution of diet and exercise to body composition. Few studies have examined these associations in the elderly, where changes occur in the body fat to muscle ratio. OBJECTIVE: The primary objective of this paper is to determine whether energy intake or physical activity are associated with body composition. Secondly, to investigate whether specific macronutrients are associated with fat or lean tissue. DESIGN: Data (n= 1404) for this cross-sectional analysis were collected from a population-based sub-sample of elderly enrollees in the Cardiovascular Health Study (CHS). Dietary intake and physical activity were assessed by questionnaires. Body composition was measured by Dual Energy X-ray Absorptiometry (DEXA). Linear regression models were used to assess the associations of diet and activity with body composition. RESULTS: Total energy intake was not associated with any of the body composition measures. Higher dietary saturated fat was associated with higher percent body mass as fat and trunk fat in both sexes (p<0.01), and in men other dietary fats were associated with body fat. In women, distance walked was inversely associated with fat masses even after adjustment for pace of walking. In both sexes, faster pace of walking was associated with lower body and fat mass (p<0.01). Lean muscle mass was not associated with physical activity or dietary intakes. CONCLUSION: Physical activity and dietary fat intake in this the elderly population were more closely associated with body fat mass than was total energy intake.

Absorptiometry, Photon↗

Self-paced resistance training and walking exercise in community-dwelling older adults: effects on neuromotor performance.

BACKGROUND: Resistance-training intervention studies have demonstrated meaningful health benefits in older adults; however, most have used exercises performed at specific intensities on expensive equipment, which limit their widespread applicability. We tested whether two self-paced, less expensive exercise protocols could be effective and safe for modifying neuromotor performance and functional capacity in community-dwelling adults 65-95 years of age. METHODS: One hundred and thirty-one subjects were randomized to a novel resistance training, walking, or control group. Subjects determined their level of resistance or walking intensity (self-paced) on a session-by-session basis. Muscle strength, balance, reaction time, stair climbing speed, and a timed pen pickup task were measured before and after the intervention period. Exercisers met three times per week for 10 months. RESULTS: Significant improvements in tandem stance and single-legged stance with eyes open times and stair climbing speed were seen in both exercise groups. In addition, resistance trainers improved their muscle strength and ability to pick up an object from the floor and reduced the number of missteps taken during tandem walking, and walkers reduced tandem walking time. Controls showed no significant improvement in any variable. CONCLUSIONS: The two self-paced exercise protocols were effective at improving neuromotor performance and functional capacity in the study sample and show promise as a safe, effective, cost-efficient, acceptable exercise model for primary and secondary prevention in the general population of community-dwelling older adults.

Aged↗

Analysis of the metabolic and ventilatory response to self-paced 12-minute treadmill walking in patients with severe chronic obstructive pulmonary disease.

BACKGROUND: The 12-minute walking test is frequently used to measure exercise capacity in patients with severe chronic obstructive pulmonary disease. However, the physiological response to this test has been the subject of limited investigation. METHODS: In this study, the metabolic and ventilatory consequences of a self-paced 12-minute treadmill walking test (WT) were measured in 17 patients with severe chronic obstructive pulmonary disease (FEV1: 40 +/- 9%) and evaluated using the physiological response to symptom-limited cycle ergometry (CE). During exercise testing, heart rate, transcutaneous oxygen saturation, and lactate concentration were measured, and oxygen consumption, carbon dioxide production, tidal volume, and breathing frequency were recorded breath by breath. RESULTS: After 4 minutes walking, the peak oxygen consumption (VO2) was already 99 +/- 11% of last-minute walking VO2. Walking speed was chosen within 2 minutes and remained stable throughout the test. The WT and CE showed similar (end-) test results for all measurements, except for a higher carbon dioxide production, venous lactate concentration, and respiratory quotient after CE. However, lactate concentration was also significantly increased after WT. Severe and prolonged desaturation was shown during walking in most patients. CONCLUSIONS: The physiological stress evoked during the WT is close to the stress developed at an incremental symptom-limited test and the relatively high metabolic and ventilatory stress is sustained from at least 4 to 12 minutes during the WT. This study has shown that anaerobic metabolism not only occurs during incremental cycle ergometry, but also during the WT.

Blood Gas Analysis↗

Obesity, weight change, and functional decline in peripheral arterial disease.

BACKGROUND: Our objectives were to determine whether obesity is associated with a greater functional decline compared with the ideal body mass index (BMI) among persons with peripheral arterial disease (PAD) and to determine the associations between weight gain and loss and functional declines in PAD. We hypothesized that baseline obesity and weight gain during follow-up would each be associated with functional declines in persons with PAD. METHODS: The design was a prospective cohort study. The subjects were 389 men and women with PAD (mean ankle-brachial index, 0.65 +/- 0.14) who were followed up prospectively for a median of 48 months. The main outcome measures were functional assessments (6-minute walk, usual- and rapid-paced 4-m walking speed, and summary performance score). Weight and height were measured at baseline and annually. Results were adjusted for age, sex, race, comorbidities, ankle-brachial index, education, leg symptoms, exercise status, depressive symptoms, pack-years of cigarette smoking, prior-year functioning, and patterns of missing data. RESULTS: Compared with those with a baseline BMI between 20 and 25 kg/m2, PAD participants with baseline BMI greater than 30 kg/m2 had a significantly greater average annual decline in 6-minute walk performance (-13.1 vs -26.5 m/y; P = .004), usual-paced 4-m walking velocity (-0.028 vs -0.055 m/s per year; P = .024), and fast-paced 4-m walking velocity (-0.053 vs -0.086 m/s per year; P = .012). Persons with weight gain between 5 and 10 pounds after baseline who walked for exercise regularly had significantly less decline in the 6-minute walk than persons without significant weight change who did not walk for exercise (P = .04). CONCLUSIONS: Obesity is associated with functional decline in persons with PAD. Walking exercise may protect against functional decline in PAD persons with modest weight gain.

Aged↗

Modulation of limb dynamics in the swing phase of locomotion.

A method was presented for quantifying cat (Felis catus) hind limb dynamics during swing phase of locomotion using a two-link rigid body model of leg and paw, which highlighted the dynamic interactions between segments. Comprehensive determination was made of cat segment parameters necessary for dynamic analysis, and regression equations were formulated to predict the inertial parameters of any comparable cat. Modulations in muscle and non-muscle components of knee and ankle joint moments were examined at two treadmill speeds using three gaits: (a) pace-like walk and trot-like walk, at 1.0 ms-1, and (b) gallop, at 2.1 ms-1. Results showed that muscle and segment interactive moments significantly effected limb trajectories during swing. Some moment components were greater in galloping than in walking, but net joint maxima were not significantly different between speeds. Moment magnitudes typically were greater for pace-like walking than for trot-like walking at the same speed. Generally, across gaits, the net and muscle moments were in phase with the direction of distal joint motion, and these same moments were out of phase with proximal joint motion. Intersegmental dynamics were not modulated exclusively by speed of locomotion, but interactive moments were also influenced significantly by gait mode.

Animals↗

Measurement of energy expenditure of daily tasks among mothers of young children.

There is currently some debate about whether the energy expenditure of domestic tasks is sufficient to confer health benefits. The aim of this study was therefore to measure the energy cost of five activities commonly undertaken by mothers of young children. Seven women with at least one child younger than five years of age spent 15 minutes in each of the following activities: sitting quietly, vacuum cleaning, washing windows, walking at moderate pace (approx 5km/hour), walking with a stroller and grocery shopping in a supermarket. Each of the six 'trials' was completed on the same day, in random order. A carefully calibrated portable gas analyser was used to measure oxygen uptake during each activity, and data were converted to units of energy expenditure (METS). Vacuum cleaning, washing windows and walking with and without a stroller were found to be 'moderate intensity activities' (3 to 6 METs), but supermarket shopping did not reach this criterion. The MET values for these activities were similar to those reported in the Compendium of Physical Activities (Ainsworth et al., 2000). However, the energy expenditures of walking, both with and without a stroller, were higher than those reported in the Compendium. The findings suggest that some of the tasks associated with domestic caring duties are conducted at an intensity which is sufficient to confer some health benefit. Such benefits will only accrue however if the daily duration of these activities is sufficient to meet current guidelines.

Activities of Daily Living↗

Relationships between physical activity and temporal-distance characteristics of walking in elderly women.

The purpose of this study was to investigate the relationships between physical activity and walking speed in women 64 years of age and over. Data were gathered from 81 nondisabled women ranging from 64.0 to 94.5 years of age. The women were categorized as sedentary, community active, or exercisers based on a combination of their living situation and level of daily activity. Subjects walked over a 3.84-m recording surface at five different paces, ranging from walking as slowly as possible to walking as quickly as possible. Actual walking speed and length of steps were measured. Stepping frequency and step length relative to leg length were derived measures. Mean walking speeds ranged from 0.43 m/s at the very slow pace to 1.42 m/s at the very fast pace. The walking speeds at the very slow pace were significantly different among the three physical activity groups. At the very slow pace, women who exercised were able to walk significantly more slowly than the other women. The groups were not significantly different at any other pace. Normal walking speeds for all groups were slower than those previously reported for younger women, with the walking speed of the fastest pace of the elderly women being closer to the normal walking speed of younger women. The results of this study indicate that physical therapists need to utilize age-appropriate values as the standard when evaluating performance. [Leiper CI, Craik RL. Relationships between physical activity and temporal-distance characteristics of walking in elderly women.

Activities of Daily Living↗

The ankle brachial index independently predicts walking velocity and walking endurance in peripheral arterial disease.

OBJECTIVES: Maintaining function among older men and women is an important public health goal as the population lives longer with chronic disease. We report the relationships between lower extremity peripheral arterial disease (PAD), PAD severity, and PAD-related symptoms with walking velocity and endurance among men and women aged 55 and older. DESIGN: A cross-sectional design. SETTING: An academic medical center. PARTICIPANTS: Participants with PAD were men and women aged 55 and older identified from a blood flow laboratory or a general medicine practice (n = 158). Randomly selected controls without PAD were identified from the general medicine practice (n = 70). MEASUREMENTS: PAD was diagnosed and quantified using the ankle brachial index (ABI). Subjects were categorized according to whether they had severe PAD (ABI <0.40), mild to moderate PAD (ABI 0.40 to <0.90), or no PAD (ABI 0.90 to <1.50). Walking endurance was assessed with the 6-minute walk. Usual walking velocity and maximal walking velocity were assessed with "usual" and "maximal" paced 4-meter walks, respectively. RESULTS: Average distances achieved in the 6-minute walk were 1569+/-390 feet for subjects with ABI 0.90-1.50, 1192+/-368 feet for subjects with ABI 0.40 to <0.90, and 942+/-334 feet for subjects with ABI < 0.40 (trend P value < .001). Walking velocities for both the usual and maximal paced 4-meter walks were slowest among subjects with ABI < 0.40 and fastest among subjects with ABI 0.90 to <1.50. Subjects with PAD who had pain at rest had slower walking velocity and poorer walking endurance than other subjects with PAD. In multiple linear regression analyses that included subjects with PAD only, ABI level was an independent predictor of 6-minute walk performance (regression coefficient = 159 ft/0.40 ABI units, P = .011), usual paced 4-meter walk (regression coefficient = .095 meters/sec/0.40 ABI units, P = .031), and maximal paced 4-meter walk (regression coefficient = .120 meters/sec/0.40 ABI units, P = .050) adjusting for age, sex, race, leg symptoms, and comorbid diseases known to affect functioning. Pain at rest was associated independently with the maximally paced 4-meter walk (-0.201 meters/sec, P = .024), but not with the other walks. CONCLUSION: ABI level has a measurable and independent association with walking endurance and both usual and maximal walking velocity. These data suggest that PAD may impair lower extremity function by diminishing function of both Type I ("slow twitch") and Type II ("fast twitch") muscle fibers. Because walking velocity has important prognostic implications for functioning, these data also suggest that ABI may be used to identify patients at increased risk of mobility loss.

Aged↗

Energy cost of treadmill and floor walking at self-selected paces.

Oxygen uptake-velocity regression equations were developed for floor and level treadmill walking by having two groups of men, aged 19-29 years (n = 20) and 55-66 years (n = 22), walk at four self-selected paces, from "rather slowly" to "as fast as possible". A two-variable quadratic model relating VO2 (ml X kg-1 X min-1) to velocity (m X s-1) was adopted for prediction purposes. However, age and fatness significantly (P less than 0.05) interacted with treadmill walking speed, while age alone significantly interacted with floor speed. In addition, a significant difference was found between the energy cost of floor and treadmill walking. For example at the normal walking speed of 1.33 m X s-1, the energy cost for the treadmill (age 55-66 years) was 10.58 ml X kg-1 X min-1 and for the floor, 11.04 ml X kg-1 X min-1 (P less than 0.05). Four quadratic equations are therefore presented, one each for floor and treadmill in each of the two age-groups. The percent variance explained was between 87 and 95% for each of these equations.

Adult↗

Randomized placebo-controlled trial of brisk walking in the prevention of postmenopausal osteoporosis.

OBJECTIVE: to evaluate the effects of brisk walking on bone mineral density in women who had suffered an upper limb fracture. DESIGN: randomized placebo-controlled trial. Assessments of bone mineral density were made before and at 1 and 2 years after intervention. Standardized and validated measures of physical capacity, self-rated health status and falls were used. SETTING: district general hospital outpatient department. SUBJECTS: 165 women drawn from local accident and emergency departments with a history of fracture of an upper limb in the previous 2 years. Women were randomly allocated to intervention (self-paced brisk walking) or placebo (upper limb exercises) groups. INTERVENTION: both groups were seen at 3-monthly intervals to assess progress, measure physical capacity and maintain enthusiasm. The brisk-walking group were instructed to progressively increase the amount and speed of walking in a manner that suited them. The upper limb exercise placebo group were asked to carry out a series of exercises designed to improve flexibility and fine hand movements, appropriate for a past history of upper limb fracture. RESULTS: drop-outs from both intervention and placebo groups were substantial (41%), although there were no significant differences in bone mineral density, physical capacity or health status between drop-outs and participants. At 2 years, among those completing the trial, bone mineral density at the femoral neck had fallen in the placebo group to a greater extent than in the brisk-walking group [mean net difference between intervention and placebo groups 0.019 g/cm2, 95% confidence interval (CI) -0.0026 to +0.041 g/cm2, P = 0.056]. Lumbar spine bone mineral density had increased to a similar extent (+0.017 g/cm2) in both groups. The cumulative risk of falls was higher in the brisk-walking group (excess risk of 15 per 100 person-years, 95% CI 1.4-29 per 100 person-years, P < 0.05). There were no significant differences in clinical or spinal x-ray fracture risk or self-rated health status between intervention and placebo groups. CONCLUSION: the promotion of exercise through brisk-walking advice given by nursing staff may have a small, but clinically important, impact on bone mineral density but is associated with an increased risk of falls. Self-paced brisk walking is difficult to evaluate in randomized controlled trials because of drop-outs, placebo group exercise, limited compliance and lack of standardization of the duration and intensity of walking. Further work is needed to evaluate the best means of safely achieving increased activity levels in different groups, such as older women and those at high risk of fractures.

Accidental Falls↗

Factor analysis of exercise capacity, dyspnoea ratings and lung function in patients with severe COPD.

In this study we aimed to determine the relationship between exercise capacity, clinical ratings of dyspnoea and lung function parameters in patients with severe chronic obstructive pulmonary disease (COPD) by means of the statistical method of factor analysis. Sixty two patients (mean age +/- SD, 66 +/- 9 yrs) in stable clinical condition, with a forced expiratory volume in one second (FEV1) < 65% of predicted were investigated. Before the study, therapy was optimized, including inhaled bronchodilators, theophylline and steroids. Exercise capacity was determined from the best 6 min walking distance achieved in five self-paced treadmill walks performed on consecutive days. Lung function testing comprised spirometry and body plethysmography. Four different tools were chosen to rate dyspnoea and quality of life: the Baseline Dyspnoea Index (BDI), the Oxygen Cost Diagram (OCD), a modified Medical Research Council (MRC) Scale, and the Chronic Respiratory Disease Questionnaire (CRQ). Principal component factor analysis revealed that the data could be reduced to three hypothetical underlying variables (factors), which accounted for 79% of the total variance. BDI, MRC, OCD, CRQ and walking distance were attributed to the first factor, forced expiratory volume in one second and airway resistance to the second factor, and lung volumes to the third factor. Thus, our data suggest that the pathophysiological condition of severe COPD is characterized by three statistically independent entities: 1) exercise capacity, dyspnoea and quality of life ratings; 2) airway obstruction; and 3) pulmonary hyperinflation.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗

Functional decline in peripheral arterial disease: associations with the ankle brachial index and leg symptoms.

CONTEXT: Among individuals with lower-extremity peripheral arterial disease (PAD), specific leg symptoms and the ankle brachial index (ABI) are cross-sectionally related to the degree of functional impairment. However, relations between these clinical characteristics and objectively measured functional decline are unknown. OBJECTIVE: To define whether PAD, ABI, and specific leg symptoms predict functional decline at 2-year follow-up. DESIGN, SETTING, AND PARTICIPANTS: Prospective cohort study among 676 consecutively identified individuals (aged > or =55 years) with and without PAD (n = 417 and n = 259, respectively), with baseline functional assessments occurring between October 1, 1998, and January 31, 2000, and follow-up assessments scheduled 1 and 2 years thereafter. PAD was defined as ABI less than 0.90, and participants with PAD were categorized at baseline into 1 of 5 mutually exclusive symptom groups. MAIN OUTCOME MEASURES: Mean annual changes in 6-minute walk performance and in usual-paced and fast-paced 4-m walking velocity, adjusted for age, sex, race, prior-year functioning, comorbid diseases, body mass index, pack-years of cigarette smoking, and patterns of missing data. RESULTS: Lower baseline ABI values were associated with greater mean (95% confidence interval) annual decline in 6-minute walk performance (-73.0 [-142 to -4.2] ft for ABI <0.50 vs -58.8 [-83.5 to -34.0] ft for ABI 0.50 to <0.90 vs -12.6 [-40.3 to 15.1] ft for ABI 0.90-1.50, P =.02). Compared with participants without PAD, PAD participants with leg pain on exertion and rest at baseline had greater mean annual decline in 6-minute walk performance (-111 [-173 to -50.0] ft vs -8.67 [-36.9 to 19.5] ft, P =.004), usual-pace 4-meter walking velocity (-0.06 [-0.09 to -0.02] m/sec vs -0.01 (-0.03 to 0.003] m/sec, P =.02), and fastest-pace 4-meter walking velocity (-0.07 [-0.11 to -0.03] m/sec vs -0.02 [-0.04 to -0.006] m/sec, P =.046). Compared with participants without PAD, asymptomatic PAD was associated with greater mean annual decline in 6-minute walk performance (-76.8 (-135 to -18.6] ft vs -8.67 (-36.9 to 19.5] ft, P =.04) and an increased odds ratio for becoming unable to walk for 6 minutes continuously (3.63; 95% confidence interval, 1.58-8.36; P =.002). CONCLUSIONS: Baseline ABI and the nature of leg symptoms predict the degree of functional decline at 2-year follow-up. Previously reported lack of worsening in claudication symptoms over time in patients with PAD may be more related to declining functional performance to than lack of disease progression.

Activities of Daily Living↗

Assessing exercise capacity, quality of life and haemodynamics in heart failure: do the tests tell us the same thing?

BACKGROUND: The objective measurement of exercise tolerance is an important component of heart failure trials. The use of laboratory-based treadmill exercise testing has attracted criticism, however, as being unrepresentative of patients' true capabilities. AIM: To examine the relationships between tests of exercise capacity, quality of life and haemodynamics in patients with stable symptomatic heart failure. METHODS: Thirty-six patients with mild-moderate chronic heart failure were studied. Exercise capacity was assessed in the laboratory by maximal treadmill tests and self-paced corridor walk tests, and in the patients' homes by hip-borne pedometers. Quality of life was assessed by a disease-specific questionnaire. Cardiac output and limb blood flow were measured by non-invasive techniques. RESULTS: Customary activity as assessed by pedometer scores correlated with quality of life questionnaire scores (r(S) = 0.47, P = 0.04), and both variables correlated with limb (calf) blood flow (pedometer scores: r(S) = 0.39, P = 0.03; quality of life scores: r(S)= 0.50, P = 0.04). The laboratory-based maximal treadmill test correlated with the self-paced corridor walk test, but neither of these tests correlated with pedometer scores, quality of life or haemodynamics. CONCLUSIONS: Different methods of assessing exercise capacity do not appear to give comparable results and bear different relationships to haemodynamic variables and quality of life. Pedometer scores of customary activity may better reflect patients' quality of life and appear to be more closely related to limb blood flow than the maximal treadmill exercise test or the corridor walk test. The sole use of laboratory-based exercise tests in therapeutic trials may give a misleading assessment of treatment efficacy in heart failure patients.

Aged↗

Self-pacing and cognitive performance while walking.

Ten hikers completed a 4 km hike on hilly terrain three times: once self-paced without load, once self-paced with a backpack load of 10% body weight, and once externally paced with a backpack load of 10% body weight. Subjects performed mental arithmetic tasks and provided ratings of perceived exertion while walking. No differences in speed or accuracy of performance of mental arithmetic problems were observed. A battery of cognitive and physical tests was performed prior to walking and after each of the three walks. Significant differences between pre-walk baselines and post-walk tests were found only for the pattern-matching task. Subjects altered their pace in response to the addition of the backpack load, and altered their speed on downhill terrain in response to external pacing. Ratings of perceived exertion were found to correlate relatively well (r = 0.80) with heart rate, but consistently underestimated actual heart rate. Underestimation was much greater for downhill than for uphill terrain. Underestimation of heart rate by rating of perceived exertion was least when subjects carried an external load of 10% body weight.

Adolescent↗