The aims were to develop and validate a VO2peak prediction equation from a treadmill running test in active male adolescents. Eighty-eight athletes (12–18 yrs.) performed a maximal exercise test on a treadmill to assess the actual VO2peak and a 20m Shuttle-Run-Test (20mST). A step-wise linear regression analysis was used and the following equation for estimation of VO2peak (mL·kg−1·min−1) = 35.477 + 1.832 × duration in min - 0.010 × duration × body mass in kg was developed. The cross-validation statistics were: R = .54, CE = 0.1 mL·kg−1·min−1, SEE = 2.5 mL·kg−1·min−1 (4.6%), and TE = 2.6 mL·kg−1·min−1 (4.9%). The cross-validation values (CE, SEE, and TE) were lower compared with those of previously published equations in adolescents that estimated VO2peak using anthropometric data, performance in 20mST, and energy cost at submaximal speeds.
Vassilis Tsiaras, Andreas Zafeiridis, Konstantina Dipla, Kostas Patras, Anastasios Georgoulis and Spiros Kellis
Felipe Alvim, Lucenildo Cerqueira, Aluízio D’Affonsêca Netto, Guilherme Leite and Adriane Muniz
This study involved a comparison of 5 kinematic-based algorithms to detect heel strike (HS) and toe-off (TO) events during human locomotion at different speeds. The objective was to assess how different running and walking speeds affect contact event determination during treadmill locomotion. Thirty male runners performed walking at 5 km/h and running at 9, 11, and 13 km/h on a treadmill. A kinematic system was used to capture the trajectories of 2 retro-reflective markers placed at the subject’s right heel and second metatarsal. A footswitch device was used to determine the “true” times of HS and TO compared with 5 kinematic-based algorithms. The results of the current study illustrated that speed influences the HS error in the vertical position and horizontal velocity algorithms, and the TO error in the vertical position and horizontal velocity algorithms. This difference was found in the transition from walking to running; however, higher running speeds did not affect the error estimation. Higher accuracy was found with combined algorithms, namely, one using vertical acceleration and position and another using horizontal and vertical position with no influence from different locomotion speeds. Therefore, these algorithms are recommended in studies where speed is self-selected because they work well for a broad range of locomotion velocities.
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 ·
David V.B. James, Leigh E. Sandals, Stephen B. Draper, Sara Maldonado-Martín and Dan M. Wood
Previously it has been observed that, in well-trained 800-m athletes, VO2max is not attained during middle-distance running events on a treadmill, even when a race-type pacing strategy is adopted. Therefore, the authors investigated whether specialization in a particular running distance (400-m or 800-m) influences the VO2 attained during running on a treadmill.
Six 400-m and six 800-m running specialists participated in the study. A 400-m trial and a progressive test to determine VO2max were completed in a counterbalanced order. Oxygen uptakes attained during the 400-m trial were compared to examine the influence of specialist event.
A VO2 plateau was observed in all participants for the progressive test, demonstrating the attainment of VO2max. The VO2max values were 56.2 ± 4.7 and 69.3 ± 4.5 mL · kg−1 · min−1 for the 400-m- and 800-m-event specialists, respectively (P = .0003). Durations for the 400-m trial were 55.1 ± 4.2 s and 55.8 ± 2.3 s for the 400-m- and 800-m-event specialists, respectively. The VO2 responses achieved were 93.1% ± 2.0% and 85.7% ± 3.0% VO2max for the 400-m- and 800-m-event specialists, respectively (P = .001).
These results demonstrate that specialist running events do appear to influence the percentage of VO2max achieved in the 400-m trial, with the 800-m specialists attaining a lower percentage of VO2max than the 400-m specialists. The 400-m specialists appear to compensate for a lower VO2max by attaining a higher percentage VO2max during a 400-m trial.
Shelby L. Francis, Ajay Singhvi, Eva Tsalikian, Michael J. Tansey and Kathleen F. Janz
Determining fitness is important when assessing adolescents with type 1 diabetes mellitus (T1DM). Submaximal tests estimate fitness, but none have been validated in this population. This study cross-validates the Ebbeling and Nemeth equations to predict fitness (VO2max (ml/kg/min)) in adolescents with T1DM.
Adolescents with T1DM (n = 20) completed a maximal treadmill test using indirect calorimetry. Participants completed one 4-min stage between 2.0 and 4.5 mph and 5% grade (Ebbeling/Nemeth protocol). Speed and grade were then increased until exhaustion. Predicted VO2max was calculated using the Ebbeling and Nemeth equations and compared with observed VO2max using paired t tests. Pearson correlation coefficients, 95% confidence intervals, coefficients of determination (R2), and total error (TE) were calculated.
The mean observed VO2max was 47.0 ml/kg/min (SD = 6.9); the Ebbeling and Nemeth mean predictions were 42.4 (SD = 9.4) and 43.5 ml/kg/min (SD = 6.9), respectively. Paired t tests resulted in statistically significant (p < .01) mean differences between observed and predicted VO2max for both predictions. The association between the Ebbeling prediction and observed VO2max was r = .90 (95% CI = 0.76, 0.96), R 2 = .81, and TE = 6.5 ml/kg/min. The association between the Nemeth prediction and observed VO2max was r = .81 (95% CI = 0.57, 0.92), R 2 = .66, and TE = 5.6 ml/kg/min.
The Nemeth submaximal treadmill protocol provides a better estimate of fitness than the Ebbeling in adolescents with T1DM.
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.
Kaixuan Shi, Xiaoli Liu, Decai Qiao and Lijuan Hou
Exercise improves motor deficits in Parkinson’s disease (PD) patients but the underlying neuronal mechanism is poorly understood. Since the striatum is critical to motor function, we have investigated the potential effects of exercise on the spiking activity of the striatal neurons in a rat model of Parkinson’s disease. Twenty-four hours after injection of 6-hydroxydopamine (6-OHDA) into the right medial forebrain bundle, rats in exercise groups were trained to exercise on a treadmill. Twenty-eight days after 6-OHDA lesion, apomorphine induced fewer rotations in the PD rats with exercise than in PD + Ex rats. Anatomical examination indicates that compared with the PD rats, PD + Ex rats had an attenuated loss of dopamine axonal fibers in the striatum and dopamine neurons in the substantia nigra pars. Equally important, the abnormal burst firing and firing rates in striatal neurons were lower in the PD + Ex rats than in the PD rats. Taken together, our results suggest that exercise has neuroprotective effects that can reduce the degeneration of the nigrostriatal dopamine system and minimize the abnormal neuronal spike firing in parkinsonian striatum, potentially contributing to exercise’s motor-improving effects in PD.
Ricky Watari, Blayne Hettinga, Sean Osis and Reed Ferber
The purpose of this study was to validate measures of vertical oscillation (VO) and ground contact time (GCT) derived from a commercially-available, torso-mounted accelerometer compared with single marker kinematics and kinetic ground reaction force (GRF) data. Twenty-two semi-elite runners ran on an instrumented treadmill while GRF data (1000 Hz) and three-dimensional kinematics (200 Hz) were collected for 60 s across 5 different running speeds ranging from 2.7 to 3.9 m/s. Measurement agreement was assessed by Bland-Altman plots with 95% limits of agreement and by concordance correlation coefficient (CCC). The accelerometer had excellent CCC agreement (> 0.97) with marker kinematics, but only moderate agreement, and overestimated measures between 16.27 mm to 17.56 mm compared with GRF VO measures. The GCT measures from the accelerometer had very good CCC agreement with GRF data, with less than 6 ms of mean bias at higher speeds. These results indicate a torsomounted accelerometer provides valid and accurate measures of torso-segment VO, but both a marker placed on the torso and the accelerometer yield systematic overestimations of center of mass VO. Measures of GCT from the accelerometer are valid when compared with GRF data, particularly at faster running speeds.
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.
Danielle M. Lambrick, Ann V. Rowlands and Roger G. Eston
This study assessed the nature of the perceived exertion response to treadmill running in 14 healthy 7–8 year-old children, using the Eston-Parfitt (E-P) Ratings of Perceived Exertion (RPE) scale and a marble dropping task. For the E-P scale and the marble dropping task, the relationships between the RPE and work rate were best described as linear (R 2 = .96) and curvilinear (R 2 = .94), respectively. This study further suggests that individual respiratory-metabolic cues (oxygen uptake: O2, heart rate: HR, ventilation: V̇E) may significantly influence the overall RPE to varying degrees in young children. The E-P scale provides an intuitively meaningful and valid means of quantifying the overall perception of exertion in young, healthy children during treadmill running. The marble dropping task is a useful secondary measure of perceived exertion, which provides further insight into the nature of the perceived exertion response to exercise in young children.