Cardiovascular responses of older adults to downhill (DTW, –10% incline) and level treadmill walking (0%) at self-selected walking speed (SSWS) were examined. Fifteen participants (age 68 ± 4 yr, height 1.69 ± 0.08 m, body mass 74.7 ± 8.1 kg) completed two 15-min walks at their SSWS (4.6 ± 0.6 km/hr). Cardiovascular responses were estimated using an arterial-volume finger clamp and infrared plethysmography. Oxygen consumption was 25% lower during DTW and associated with lower values for stroke volume (9.9 ml/beat), cardiac output (1.0 L/min), arteriovenous oxygen difference (a-v O2 diff, 2.4 ml/L), and systolic blood pressure (10 mmHg), with no differences in heart rate or diastolic and mean arterial blood pressure. Total peripheral resistance (TPR) was higher (2.11 mmHg) during DTW. During downhill walking, an exercise performed with reduced cardiac strain, endothelial changes, and reduced metabolic demand may be responsible for the different responses in TPR and a-v O2 diff. Future work is warranted on whether downhill walking is suitable for higher risk populations.
Mandy L. Gault, Richard E. Clements and Mark E.T. Willems
John M. Schuna Jr., Tiago V. Barreira, Daniel S. Hsia, William D. Johnson and Catrine Tudor-Locke
Energy expenditure (EE) estimates for a broad age range of youth performing a variety of activities are needed.
106 participants (6–18 years) completed 6 free-living activities (seated rest, movie watching, coloring, stair climbing, basketball dribbling, jumping jacks) and up to 9 treadmill walking bouts (13.4 to 120.7 m/min; 13.4 m/min increments). Breath-by-breath oxygen uptake (VO2) was measured using the COSMED K4b2 and EE was quantified as youth metabolic equivalents (METy1:VO2/measured resting VO2, METy2:VO2/estimated resting VO2). Age trends were evaluated with ANOVA.
Seated movie watching produced the lowest mean METy1 (6- to 9-year-olds: 0.94 ± 0.13) and METy2 values (13- to 15-year-olds: 1.10 ± 0.19), and jumping jacks produced the highest mean METy1 (13- to 15-year-olds: 6.89 ± 1.47) and METy2 values (16- to 18-year-olds: 8.61 ± 2.03). Significant age-related variability in METy1 and METy2 were noted for 8 and 2 of the 15 evaluated activities, respectively.
Descriptive EE data presented herein will augment the Youth Compendium of Physical Activities.
Rishann Nielson, Pat R. Vehrs, Gilbert W. Fellingham, Ronald Hager and Keven A. Prusak
The purposes of this study were to determine the accuracy and reliability of step counts and energy expenditure as estimated by a pedometer during treadmill walking and to clarify the relationship between step counts and current physical activity recommendations.
One hundred males (n = 50) and females (n = 50) walked at stride frequencies (SF) of 80, 90, 100, 110, and 120 steps/min, during which time step counts and energy expenditure were estimated with a Walk4Life Elite pedometer.
The pedometer accurately measured step counts at SFs of 100, 110, and 120 steps/min, but not 80 and 90 steps/min. Compared with energy expenditure as measured by a metabolic cart, the pedometer significantly underestimated energy expenditure at 80 steps/min and significantly overestimated measured energy expenditure at 90, 100, 110, and 120 steps/ min.
The pedometers’ inability to accurately estimate energy expenditure cannot be attributed to stride length entered into the pedometer or its ability to measure step counts. Males met 3 criteria and females met 2 criteria for moderate-intensity physical activity at SF of 110 to 120 steps/min. These results provide the basis for defining moderate-intensity physical activity based on energy expenditure and step counts and may lead to an appropriate steps/day recommendation.
Phillip D. Tomporowski and Michel Audiffren
Thirty-one young (mean age = 20.8 years) and 30 older (mean age = 71.5 years) men and women categorized as physically active (n = 30) or inactive (n = 31) performed an executive processing task while standing, treadmill walking at a preferred pace, and treadmill walking at a faster pace. Dual-task interference was predicted to negatively impact older adults’ cognitive flexibility as measured by an auditory switch task more than younger adults; further, participants’ level of physical activity was predicted to mitigate the relation. For older adults, treadmill walking was accompanied by significantly more rapid response times and reductions in local- and mixed-switch costs. A speed-accuracy tradeoff was observed in which response errors increased linearly as walking speed increased, suggesting that locomotion under dual-task conditions degrades the quality of older adults’ cognitive flexibility. Participants’ level of physical activity did not influence cognitive test performance.
Daniel E. Lidstone, Justin A. Stewart, Reed Gurchiek, Alan R. Needle, Herman van Werkhoven and Jeffrey M. McBride
e3182456057 11. Blacker SD , Fallowfield JL , Bilzon JL , Willems ME . Physiological responses to load carriage during level and downhill treadmill walking . Medicina Sportiva . 2009 ; 13 ( 2 ): 116 – 124 . 10.2478/v10036-009-0018-1 10.2478/v10036-009-0018-1 12. Grenier JG , Millet
Christopher A. Miller, Alan H. Feiveson and Jacob J. Bloomberg
Gait kinematics have been shown to vary with speed and visual-target fixation distance, but their combined effects on toe trajectory during treadmill walking are not known. The purpose of this investigation was to determine the role of walking speed and target distance on vertical toe trajectory during treadmill walking. Subjects walked on a treadmill at five speeds while performing a dynamic visual-acuity task at both “far” and “near” target distances (ten trials total). The analysis concentrated on three specific toe trajectory events during swing: the first peak toe height just after toe-off; the minimum toe height (toe clearance), and the second peak toe height just before heel strike. With increasing speed, toe clearance decreased and the peak toe height just before heel strike increased. Only the peak toe height just after toe-off was significantly changed between the near-target and far-target tasks, though the difference was small. Therefore, walking speed and visual-fixation distance cannot be neglected in the analysis of toe trajectory. Otherwise, differences observed between populations may be attributed to age- or clinically related factors, instead of disparities of speed or target-fixation distance.
Tatsuhisa Takahashi, Akiyoshi Okada, Jun-ichiro Hayano and Nobuo Takeshima
To determine water immersion’s effect on heart rate (HR) and vagal tone, the authors examined HR and high-frequency R-R-interval variability in 7 healthy older adults at rest and during treadmill walking, starting at 3.0 km/hr and increasing 0.5 km/hr every 3 min at a 5% grade to exhaustion. Participants performed the test on land and then immersed in water to the xiphoid. HR at rest did not differ between water and land. During walking at 3.0 km/min, HR was significantly lower in water than on land, whereas at 4.5 and 5.0 km/min it was significantly higher (each p < .05). Peak HR at exhaustion was not significantly different between water and land. High-frequency amplitudes at rest and during exercise in water were not significantly different from those on land. The results suggest that resting vagus tone and vagal changes in response to walking exercise in elderly adults are not greatly affected by water immersion.
Joanne Kraenzle Schneider and Kenneth H. Pitetti
The purpose of this study was to compare measured
Hanatsu Nagano, Rezaul K. Begg, William A. Sparrow and Simon Taylor
Although lower limb strength becomes asymmetrical with age, past studies of aging effects on gait biomechanics have usually analyzed only one limb. This experiment measured how aging and treadmill surface influenced both dominant and nondominant step parameters in older (mean 74.0 y) and young participants (mean 21.9 y). Step-cycle parameters were obtained from 3-dimensional position/time data during preferred-speed walking for 40 trials along a 10 m walkway and for 10 minutes of treadmill walking. Walking speed (young 1.23 m/s, older 1.24 m/s) and step velocity for the two age groups were similar in overground walking but older adults showed significantly slower walking speed (young 1.26 m/s, older 1.05 m/s) and step velocity on the treadmill due to reduced step length and prolonged step time. Older adults had shorter step length than young adults and both groups reduced step length on the treadmill. Step velocity and length of older adults’ dominant limb was asymmetrically larger. Older adults increased the proportion of double support in step time when treadmill walking. This adaptation combined with reduced step velocity and length may preserve balance. The results suggest that bilateral analyses should be employed to accurately describe asymmetric features of gait especially for older adults.
David V.B. James, Linda J. Reynolds and Sara Maldonado-Martin
Heart rate variability (HRV) has been promoted as a noninvasive method of evaluating autonomic influence on cardiac rhythm. Although female subjects predominate in the walking studies, no study to date has examined the influence of the duration of a moderate intensity walking physical activity bout on HRV in this population.
Twelve healthy physically active middle-aged women undertook 2 conditions; 20min (W20) and 60min (W60) bouts of walking on a treadmill. Resting HRV measures were obtained before (−1 h), and 1 h and 24 h after the walking bouts.
Mean NN interval (ie, normal-to-normal intervals between adjacent QRS complexes) was significantly lower (P = .017) at +1 h in W60 (832, 686−979ms) compared with W20 (889, 732−1046ms). A borderline main effect for time was observed for both the SDNN intervals in W60 (P = .056), and for low frequency (LFabs) power in W60 (P = .047), with post hoc tests revealing a significant increase between −1 h (51, 33−69 ms and 847, 461−1556 ms2) and +1 h (65, 34−97ms and 1316, 569−3042 ms2) for SDNN and LFabs power, respectively, but no increase at +24h compared with −1 h.
It appears that a walking bout of 60 min duration does alter cardiac autonomic influence in healthy active women, and this alteration is not evident after 20 min of walking. Given the rather subtle effect, further studies with larger sample sizes are required to explore the nature of the changes in cardiac autonomic influence following a prolonged bout of walking.