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Hazzaa M. Al-Hazzaa, Saeed A. Al-Refaee, Muhammed A. Sulaiman, Ma’ed Y. Dafterdar, Abdullah S. Al-Herbish and Andrew C. Chukwuemeka

The purpose of this study was to examine the maximal cardiorespiratory responses of trained adolescent male swimmers (SWM, N = 18), soccer players (SOC, N = 18), and moderately active reference subjects (CON, N = 16) to treadmill running (TRD) and arm ergometry (ARM). Mean values (±SD)for skeletal age were similar among the three groups (12.5± 1.9, 12.7 ± 1.1, and 12.5 ± 1.6 years, for the SWM, SOC, and CON, respectively). Allometric scaling procedures, relating VO2max and body mass, were used and mass exponents of .80 and .74 were identified for TRD and ARM data, respectively. During TRD testing SOC attained significantly higher VO2max values when expressed in ml · kg−1 · min−1, or ml · kg−0.80 · min−1 than the other two groups. However, during ARM testing, the SWM achieved significantly higher VO2peak values (ml · kg−0.74 · min−1 and scaled to arm-CSA) than SOC. The ratio of ARM-VAT to TRD-VAT was significantly higher in SWM (50.1± 9%) compared to SOC (41.2±5%), or CON (41.9 ± 6%).

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Kenneth H. Pitetti, A. Lynn Millar and Bo Fernhall

The purpose of this study was to compare test-retest reliability when measuring peak physiological capacities of children and adolescents (age = 13.6 ± 2.9 yr) with mental retardation (MR) and their peers (12.0 ± 2.9 yr) without mental retardation (NMR) using a discontinuous treadmill (TM) protocol. Forty-six participants (23 MR = 12 male and 11 female; 23 NMR = 12 male and 11 female) completed two peak performance treadmill tests with 3 to 7 days of rest between tests. Physiological values measured included V̇O2peak (1 $$ min-1 and ml $$ kg-1 $$ min-1), V̇Epeak (1 $$ mhr-1), HRpeak (bpm), and RER (V̇O2 $$ V̇O2 -1). Test-retest reliability coefficients ranged from .85 to .99 for participants with MR and from .55 to .99 for participants without MR. Test reliability and accuracy in the present study does not appear to differ between the NMR and MR participants.

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Joshua M. Thomas and Timothy R. Derrick

The purpose of this research was to determine the effects of step uncertainty on shock attenuation and knee/subtalar synchrony. Uncertainty was manipulated by decreasing the intensity of light and introducing bumps to the running surface. Twelve experienced distance runners ran at their chosen pace on a treadmill with two surfaces (smooth and irregular) and three light intensities (light, medium, dark). Knee angle, subtalar angle, leg impacts, and head impacts were recorded at 1,000 Hz. Heart rate was also monitored. Injury potential was assessed by evaluating the impacts and asynchronous activity between the knee and subtalar joint. Stride length was not influenced by either source of uncertainty. Heart rate increased with the intensity of light on the smooth running surface but decreased with the intensity of light on the irregular surface. The knee was more flexed at heel contact during the irregular surface conditions but was not affected by the intensity of light. This decreased the effective mass of the impact and allowed greater peak leg accelerations and greater impact attenuation during irregular surface running. There was a decrease in the rearfoot angle at contact on the irregular surface that approached significance (p = 0.056). Knee/subtalar asynchrony increased with the intensity of light on the smooth surface but decreased on the irregular surface. It appears that participants used the knee joint to adapt to the irregular surface and thus accommodate changes in the terrain. The subtalar joint may have become more stable during irregular surface running to minimize the chance of inversion sprains. The effects of intensity of light were small and generally mediated the irregular surface effects. Overall, these adaptations likely reduced the potential for injury during irregular surface running but may have been detrimental to performance.

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Hervé Assadi and Romuald Lepers

Purposes:

To compare the physiological responses and maximal aerobic running velocity (MAV) during an incremental intermittent (45-s run/15-s rest) field test (45-15FIT) vs an incremental continuous treadmill test (TR) and to demonstrate that the MAV obtained during 45-15FIT (MAV45-15) was relevant to elicit a high percentage of maximal oxygen uptake (VO2max) during a 30-s/30-s intermittent training session.

Methods:

Oxygen uptake (VO2), heart rate (HR), and lactate concentration ([La]) were measured in 20 subjects during 2 maximal incremental tests and four 15-min intermittent tests. The time spent above 90% and 95% VO2max (t90% and t95% VO2max, respectively) was determined.

Results:

Maximal physiological parameters were similar during the 45-15FIT and TR tests (VO2max 58.6 ± 5.9 mL · kg−1 · min−1 for TR vs 58.5 ± 7.0 mL · kg−1 · min−1 for 45-15FIT; HRmax 200 ± 8 beats/min for TR vs 201 ± 7 beats/min for 45-15FIT). MAV45-15 was significantly (P < .001) greater than MAVTR (17.7 ± 1.1 vs 15.6 ± 1.4 km/h). t90% and t95% VO2max during the 30-s/30-s performed at MAVTR were significantly (P < .01) lower than during the 30-s/30-s performed at MAV45-15. Similar VO2 during intermittent tests performed at MAV45-15 and at MAVTR can be obtained by reducing the recovery time or using active recovery.

Conclusions:

The results suggested that the 45-15FIT is an accurate field test to determine VO2max and that MAV45-15 can be used during high-intensity intermittent training such as 30-s runs interspersed with 30-s rests (30-s/30-s) to elicit a high percentage of VO2max.

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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.

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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.

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Ian G. Campbell, Clyde Williams and Henryk K.A. Lakomy

The purpose was to examine selected physiological responses of endurance-trained male wheelchair athletes in different Paralympic racing classes (T2, n = 3; T3, n = 8; T4, n = 7) during a 10-km treadmill time trial (TM:10-km). Peak oxygen uptake (V̇O2 peak) was determined, and a TM:10-km was completed on a motorized treadmill. From this, % V̇O2peak utilized and the relationship between V̇O2peak and TM:10-km were established. During the TM:10-km, the following dependent variables were examined: propulsion speed, oxygen uptake, respiratory exchange ratio, and heart rate. The results showed athletes utilize a high % V̇O2peak (78.4 –13.6%) during the TM:10-km. There was a moderate correlation (r = -.57, p < .01) between VO2peak and TM:10-km. No physiological differences were found between the paraplegic racing classes (T3, T4), which suggests that there is some justification in amalgamating these racing classes for endurance events.

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Yumeng Li, Rumit S. Kakar, Marika A. Walker, Yang-Chieh Fu, Timothy S. Oswald, Cathleen N. Brown and Kathy J. Simpson

axial rotation. 8 For treadmill running, compared to healthy controls, Kakar and colleagues found that SF-AIS individuals demonstrated less lateral flexion of the upper trunk 9 and reduced ankle plantar flexion displacement, though a greater hip flexion angle during the stance phase. 11 SF

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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.

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Costas Chryssanthopoulos, Clyde Williams, Wendy Wilson, Lucy Asher and Lynda Hearne

The purpose of this study was to compare the effects of a carbohydrate-electrolyte solution, ingested during exercise, with the effects of a preexercise carbohydrate meal on endurance running performance. Ten endurance-trained males completed two 30-km treadmill runs. In one trial subjects consumed a placebo solution 4 hr before exercise and a carbohydrate-electrolyte solution immediately before exercise and every 5 km (C). In the other trial, subjects consumed a 4-hr preexercise high-carbohydrate meal and water immediately before exercise and every 5 km (M). Performance times were identical for M and C, and there was no difference in the self-selected speeds. Oxygen uptake, heart rates, perceived rate of exertion, and respiratory exchange ratios were also similar. However, blood glucose concentration was higher in C during the first 20 km of the 30-km run. In M, blood glucose concentration was maintained above 4.5 mmol · L1 throughout exercise. Thus, the two conditions produced the same 30-km treadmill running performance time.