Research into supplementation with sodium phosphate has not investigated the effects of a repeated supplementation phase. Therefore, this study examined the potential additive effects of repeated sodium phosphate (SP) supplementation on cycling time-trial performance and peak oxygen uptake (VO2peak). Trained male cyclists (N = 9, M ± SD VO2peak = 65.2 ± 4.8 ml · kg−1 · min−1) completed baseline 1,000-kJ time-trial and VO2peak tests separated by 48 hr, then ingested either 50 mg · kg fat-free mass−1 · d−1 of tribasic SP or a combined glucose and NaCl placebo for 6 d before performing these tests again. A 14-d washout period separated the end of one loading phase and the start of the next, with 2 SP and 1 placebo phase completed in a counterbalanced order. Although time-trial performance (55.3–56.5 min) was shorter in SP1 and SP2 (~60–70 s), effect sizes and smallest-worthwhile-change values did not differ in comparison with baseline and placebo. However, mean power output was greater than placebo during time-trial performance at the 250-kJ and 500-kJ time points (p < .05) after the second SP phase. Furthermore, mean VO2peak values (p < .01) were greater after the SP1 (3.5–4.3%), with further improvements (p < .01) found in SP2 (7.1–7.7%), compared with baseline and placebo. In summary, repeated SP supplementation, ingested either 15 or 35 d after initial loading, can have an additive effect on VO2peak and possibly time-trial performance.
Cameron P. Brewer, Brian Dawson, Karen E. Wallman and Kym J. Guelfi
Mitsuo Neya, Taisuke Enoki, Nao Ohiwa, Takashi Kawahara and Christopher J. Gore
To quantify the changes of hemoglobin mass (Hbmass) and maximum oxygen consumption (VO2max) after 22 days training at 1300–1800 m combined with nightly exposure to 3000-m simulated altitude. We hypothesized that with simulated 3000-m altitude, an adequate beneficial dose could be as little as 10 h/24 h.
Fourteen male collegiate runners were equally divided into 2 groups: altitude (ALT) and control (CON). Both groups spent 22 days at 1300–1800 m. ALT spent 10 h/night for 21 nights in simulated altitude (3000 m), and CON stayed at 1300 m. VO2max and Hbmass were measured twice before and once after the intervention. Blood was collected for assessment of percent reticulocytes (%retics), serum erythropoietin (EPO), ferritin, and soluble transferrin receptor (sTfR) concentrations.
Compared with CON there was an almost certain increase in absolute VO2max (8.6%, 90% confidence interval 4.8–12.6%) and a likely increase in absolute Hbmass (3.5%; 0.9–6.2%) at postintervention. The %retics were at least very likely higher in ALT than in CON throughout the 21 nights, and sTfR was also very likely higher in the ALT group until day 17. EPO of ALT was likely higher than that of CON on days 1 and 5 at altitude, whereas serum ferritin was likely lower in ALT than CON for most of the intervention.
Together the combination of the natural and simulated altitude was a sufficient total dose of hypoxia to increase both Hbmass and VO2max.
James S. Hogg, James G. Hopker and Alexis R. Mauger
The novel self-paced maximal-oxygen-uptake (VO2max) test (SPV) may be a more suitable alternative to traditional maximal tests for elite athletes due to the ability to self-regulate pace. This study aimed to examine whether the SPV can be administered on a motorized treadmill.
Fourteen highly trained male distance runners performed a standard graded exercise test (GXT), an incline-based SPV (SPVincline), and a speed-based SPV (SPVspeed). The GXT included a plateau-verification stage. Both SPV protocols included 5 × 2-min stages (and a plateau-verification stage) and allowed for self-pacing based on fixed increments of rating of perceived exertion: 11, 13, 15, 17, and 20. The participants varied their speed and incline on the treadmill by moving between different marked zones in which the tester would then adjust the intensity.
There was no significant difference (P = .319, ES = 0.21) in the VO2max achieved in the SPVspeed (67.6 ± 3.6 mL · kg−1 · min−1, 95%CI = 65.6–69.7 mL · kg−1 · min−1) compared with that achieved in the GXT (68.6 ± 6.0 mL · kg−1 · min−1, 95%CI = 65.1–72.1 mL · kg−1 · min−1). Participants achieved a significantly higher VO2max in the SPVincline (70.6 ± 4.3 mL · kg−1 · min−1, 95%CI = 68.1–73.0 mL · kg−1 · min−1) than in either the GXT (P = .027, ES = 0.39) or SPVspeed (P = .001, ES = 0.76).
The SPVspeed protocol produces VO2max values similar to those obtained in the GXT and may represent a more appropriate and athlete-friendly test that is more oriented toward the variable speed found in competitive sport.
Stephen F. Figoni, Richard A. Boileau, Benjamin H. Massey and Joseph R. Larsen
The purpose of this study was to compare quadriplegic and able-bodied men on selected cardiovascular and metabolic responses to arm-crank ergometry at the same rate of oxygen consumption (V̇O2). Subjects included 11 untrained, spinal cord-injured, C5–C7 complete quadriplegic men and 11 untrained, able-bodied men of similar age (27 years), height (177 cm), and mass (65 kg). Measurement techniques included open-circuit spirometry, impedance cardiography, and electrocardiography. Compared with the able-bodied group, at the V̇O2 of 0.5 L/min, the quadriplegics displayed a significantly higher mean heart rate and arteriovenous O2 difference, lower stroke volume and cardiac output, and similar myocardial contractility. These results suggest that quadriplegic men achieve an exercise-induced V̇O2 of 0.5 L/min through different central cardiovascular adjustments than do able-bodied men. Quadriplegics deliver less O2 from the heart toward the tissues but extract more O2 from the blood. Tachycardia may contribute to low cardiac preload and low stroke volume, while paradoxically tending to compensate for low stroke volume by minimizing reduction of cardiac output.
J. Mark Davis, Catherine J. Carlstedt, Stephen Chen, Martin D. Carmichael and E. Angela Murphy
Quercetin, a natural polyphenolic flavonoid substance present in a variety of food plants, has been shown in vitro and in animal studies to have widespread health and performance benefits resulting from a combination of biological properties, including antioxidant and anti-inflammatory activity, as well as the ability to increase mitochondrial biogenesis. Little is known about these effects in humans, however, especially with respect to exercise performance. The authors determined whether quercetin ingestion would enhance maximal aerobic capacity and delay fatigue during prolonged exercise in healthy but untrained participants. Twelve volunteers were randomly assigned to 1 of 2 treatments: (a) 500 mg of quercetin twice daily dissolved in vitamin-enriched Tang or (b) a nondistinguishable placebo (Tang). Baseline VO2max and bike-ride times to fatigue were established. Treatments were administered for a period of 7 days using a randomized, double-blind, placebo-controlled, crossover study design. After treatment both VO2max and ride time to fatigue were determined. Seven days of quercetin feedings were associated with a modest increase in VO2max (3.9% vs. placebo; p < .05) along with a substantial (13.2%) increase in ride time to fatigue (p < .05). These data suggest that as little as 7 days of quercetin supplementation can increase endurance without exercise training in untrained participants. These benefits of quercetin may have important implications for enhancement of athletic and military performance. This apparent increase in fitness without exercise training may have implications beyond that of performance enhancement to health promotion and disease prevention.
Andrea T. White, C. Steven Fehlauer, Rita Hanover, Stephen C. Johnson and Robert E. Dustman
Older individuals arc more likely than younger adults to exhibit symptoms of exercise intolerance at high work rates. The risks of maximal exercise in older adults increase proportionally as the number of health difficulties increase. In this study, the effects of health status, age, and gender on older adults’ ability to attain V̇O2max are examined. Sedentary volunteers (60 women, 45 men), mean age 67 ± 5 years (range 57-78 years), participated in graded maximal exercise tests on a combined arm and leg cycle ergometer. Subjects were classified into three groups based on test termination reason: attainment of V̇O2max (MAX), symptom-limited (SX), or EKG-limited (EKG). Sixty percent of men and 40% of women were classified as MAX, while 48% of women and 27% of men were characterized as SX. Thirteen percent of men and 12% of women had EKG-limited exercise tests. Those in the EKG group reported significantly more diagnoses than subjects in the MAX group (2.7 vs. 1.4. p < .05). The number of medications reported and age of the subjects did not differ across test termination categories.
Stamatis Agiovlasitis, Kenneth H. Pitetti, Myriam Guerra and Bo Fernhall
This study examined whether 20-m shuttle-run performance, sex, body mass index (BMI), age, height, and weight are associated with peak oxygen uptake (VO2peak) in youth with Down syndrome (DS; n = 53; 25 women, age 8–20 years) and whether these variables can be used to develop an equation to predict VO2peak. BMI, 20-m shuttle-run performance, and sex were significantly associated with VO2peak in youth with DS, whereas age, height, and weight were not. A regression model included only shuttle-run performance as a significant predictor of VO2peak; however, the developed prediction equation had low individual predictability. Therefore, 20-m shuttle-run performance alone does not provide valid prediction of VO2peak in youth with DS. Sex, BMI, age, height, and weight do not improve the prediction of VO2peak.
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.
Sock Miang Teo-Koh and Jeffrey A. McCubbin
The purpose of this study was to determine the relationship between peak VO2 and the 1-mile walk test (WALK) performance of forty 12–17-year-old males (mean age = 14.13 years) with mental retardation (mean IQ = 50). Test-retest reliability of the WALK was high for WALK times (R = .97), WALK End-HR (R = .88), and WALK HRpeak (R = .92). Test-retest reliability of relative peak VO2 was .90. Partial correlation analysis indicated that when weight and various combinations of variables with weight were held constant, the relationship between WALK time and peak VO2 was strengthened. Multiple regression analysis of WALK performance variables and peak VO2 measures indicated the best model for estimating relative peak VO2: VO2peak = 95.56 − 3.345 (walk time) − 0.174 (WT) and the best model for estimating absolute peak VO2: VO2peak = 2.90 − .176 (walk rime) + .031 (WT). Results indicated the WALK as a reliable field test for the sample tested.
Stephen B. Draper, Dan M. Wood, Jo Corbett, David V.B. James and Christopher R. Potter
We tested the hypothesis that prior heavy-intensity exercise reduces the difference between asymptotic oxygen uptake (VO2) and maximum oxygen uptake (VO2max) during exhaustive severe-intensity running lasting ≍2 minutes. Ten trained runners each performed 2 ramp tests to determine peak VO2 (VO2peak) and speed at venti-latory threshold. They performed exhaustive square-wave runs lasting ≍2 minutes, preceded by either 6 minutes of moderate-intensity running and 6 minutes rest (SEVMOD) or 6 minutes of heavy-intensity running and 6 minutes rest (SEVHEAVY). Two transitions were completed in each condition. VO2 was determined breath by breath and averaged across the 2 repeats of each test; for the square-wave test, the averaged VO2 response was then modeled using a monoexponential function. The amplitude of the VO2 response to severe-intensity running was not different in the 2 conditions (SEVMOD vs SEVHEAVY; 3925 ± 442 vs 3997 ± 430 mL/min, P = .237), nor was the speed of the response (τ; 9.2 ± 2.1 vs 10.0 ± 2.1 seconds, P = .177). VO2peak from the square-wave tests was below that achieved in the ramp tests (91.0% ± 3.2% and 92.0% ± 3.9% VO2peak, P < .001). There was no difference in time to exhaustion between conditions (110.2 ± 9.7 vs 111.0 ± 15.2 seconds, P = .813). The results show that the primary VO2 response is unaffected by prior heavy exercise in running performed at intensities at which exhaustion will occur before a slow component emerges.