Acute Hypotensive Response to Continuous and Accumulated Isocaloric Aerobic Bouts.

Evidence indicates that chronic reductions in blood pressure (BP) due to aerobic exercise depend on the ability to induce post-exercise hypotension (PEH) after each training bout. The purpose of this study was to investigate PEH after isocaloric bouts of continuous and accumulated running. 10 healthy pre-hypertensive men (aged 27.6±3.5 years) performed the following bouts of exercise: a) A continuous bout (CONT) expending a total of 400 kcal; and b) An accumulated bout split into 2×200 kcal (INTER1 and INTER2) to total 400 kcal at 75% of oxygen uptake reserve. BP, mean arterial pressure (MAP) and heart rate variability were monitored 10 min before and 60 min after control and all exercise conditions. The decrease in MAP over time after continuous (400 kcal) and accumulated (2×200 kcal) bouts of exercise was more pronounced than during control (mean diff between 1.6 and 5.4 mmHg, P≤0.01), although the magnitude of change was similar between continuous and accumulated bouts (mean diff=0.1 mmHg, P=0.79). Concomitant to the PEH, sympathovagal balance was inversely related to changes in MAP after isocaloric bouts performed continuously and cumulatively (r=- 0.72 and-0.85, P=0.019 and 0.002, respectively). In conclusion, BP decreased to similar levels after continuous and accumulated acute aerobic exercise matched for total energy expenditure. Our findings also indicate that the recovery pattern of cardiac autonomic activity may have an important role in eliciting PEH.

Patients' views of physical activity whilst living with and beyond head and neck cancer.

Exercise is an important component of recovery following cancer. Head and neck cancer (HNC) patients typically report low levels of engagement in exercise initiatives. The aim of this study was to give insight into HNC patients' reflections on how and why they would be interested in participating in an exercise programme. A stratified sample of 51 patients based on age, gender and initial interest in an exercise programme was selected from 430 postal survey respondents. Twenty-five took part in a semi-structured telephone interview. There was responder bias with females, younger patients, and those already participating in or interested in an exercise programme being over-represented. The responders in this study highlighted issues related to physical activity levels, perceived ability to meet physical activity guidelines for cancer survivors, perceived exercise benefits, perceived exercise barriers, and advice to others diagnosed with cancer. The findings support the premise of personalized interventions tailored towards the specific needs of the patient, supported by patient peers to emphasize the benefits and help motivate patients to take part. In order to promote engagement in exercise there needs to be collaborative, culturally sensitive and individualized approaches, in order to address the specific barriers experienced by HNC patients.

Metabolic alkalosis, recovery and sprint performance.

Pre-exercise alkalosis and an active recovery improve the physiological state of recovery through slightly different mechanisms (e. g. directly increasing extracellular bicarbonate (HCO3 (-)) vs. increasing blood flow), and combining the two conditions may provide even greater influence on blood acid-base recovery from high-intensity exercise. Nine subjects completed four trials (Placebo Active ( PLAC A), sodium bicarbonate (NaHCO3) Active ( BICARB A), Placebo Passive ( PLAC P) and NaHCO3 Passive ( BICARB P)), each consisting of three, 30-s maximal efforts with a three min recovery between each effort. Pre-exercisealkalosis was evident in both NaHCO3 conditions, as pH and HCO3 (-) were significantly higher than both Placebo conditions (pH: 7.46 ± 0.04 vs. 7.39 ± 0.02; HCO3 (-): 28.8 ± 1.9 vs. 23.2 ± 1.4 mmol·L (-1); p<0.001). In terms of performance, significant interactions were observed for average speed (p<0.05), with higher speeds evident in the BICARB A condition (3.9 ± 0.3 vs. 3.7 ± 0.4 m·s (-1)). Total distance covered was different (p=0.05), with post hoc differences evident between the BICARB A and PLAC P conditions (368 ± 33 vs. 364 ± 35 m). These data suggest that successive 30-s high intensity performance may be improved when coupled with NaHCO3 supplementation.

Influence of cardiopulmonary exercise testing protocol and resting VO(2) assessment on %HR(max), %HRR, %VO(2max) and %VO(2)R relationships.

The findings of previous studies investigating the strength of the relationships between the percentages of maximal heart rate (%HR(max)), heart rate reserve (%HRR), maximal oxygen uptake (%VO(2max)), and oxygen uptake reserve (%VO(2)R) have been equivocal. This inconsistency between studies could largely be due to differences in methodology. The purpose of this study was therefore to determine whether different VO(2max) test protocols and resting VO(2) assessment influence the relationships between the %HR(max), %HRR, %VO(2max), and %VO(2)R. Thirty-three young men performed maximal treadmill protocols (ramp, Bruce) to assess HR(max) and VO(2max). Resting VO(2) was assessed as follows: a) resting VO(2standard), using strict criteria (24 h exercise abstention, alcohol, soft drinks, or caffeine; 8 h fasting; 30 min assessment); b) resting VO(2sitting) and; c) resting VO(2standing) (both 5 min before exercise testing). The %HRR was closer to %VO(2max) than to %VO(2)R, especially in the ramp protocol (p<0.001). In the Bruce protocol, relationships were closer to the identity line, and there was no significant difference between %HRR and %VO(2max), or %VO(2)R. The VO(2max) was significantly higher in the ramp protocol compared to the Bruce protocol (p<0.001). In both protocols resting VO(2) assessment produced no significant difference in the intercepts and slopes of the %HRR-%VO(2)R relationships obtained from individual regression models. The %VO(2)R calculated using resting VO(2standard) was closer to %HRR compared to VO(2sitting) and VO(2standing). The premise that %HRR is more strongly related to %VO(2)R than to %VO(2max) was not confirmed. Methodological differences should be considered when interpreting previous studies investigating %HR(max), %HRR, %VO(2max), and %VO(2)R relationships.

Emergence of the verification phase procedure for confirming 'true' VO(2max).

Traditional (.)VO(2max) criteria are typically based on attainment of a (.)VO2 plateau, and threshold values for the respiratory exchange ratio, heart rate and blood lactate concentration. Despite long-standing criticisms directed at these criteria, their use remains widespread. This article discusses an alternative procedure, termed the verification phase, for confirming the attainment of true (.)VO(2max). Following a continuous incremental exercise test to the limit of tolerance and appropriate recovery period, the verification phase is performed and is characterized by a supramaximal square wave exercise bout. Consistent peak (.)VO2 values in the incremental and verification phases, confirms that a true (.)VO(2max) has been attained. Six recent studies investigated the utility of the verification phase for evaluating true (.)VO(2max). These studies consistently found small insignificant mean differences between the maximal (.)VO2 attained in the incremental and verification phases. However, this group mean approach does not identify individual subjects who may not have attained a true (.)VO(2max). Notably, only one of the six studies reported a criterion threshold to verify the (.)VO(2max) of individual subjects. Further research is required to investigate the utility of different verification phase procedures and to establish a suitable verification criterion threshold for confirming true VO(2max).

Release of VCAM-1 associated endothelial microparticles following simulated SCUBA dives.

Microparticles (MP) are shed into the circulation from endothelium following activation or apoptosis. Vascular cell adhesion molecule-1 (VCAM-1) is expressed on endothelial cells following activation and here we report quantification of VCAM-1 positive microparticles (VCAM + MP) following simulated SCUBA dives, breathing either air or oxygen. VCAM + MP were quantified pre-dive (09:00 and 13:00) and post-dive (+1, +3 and +15 h) on both air and oxygen dives and compared with control samples taken from the same subjects. VCAM + MP followed a similar trend in all experiments, however both dives caused a change in endothelial state, as measured by VCAM + MP. A significant increase in VCAM + MP was observed 1 h post-air dive relative to the control (p = 0.013), which was not observed after the oxygen dive (p = 0.095). Oxidative stress (TBARS) was correlated with VCAM + MP. Data presented highlights the potential of MP as a biological marker of both endothelial state and decompression illness.

The effects of caffeine ingestion on time trial cycling performance.

AIM: The purpose of this work was to determine the effects of caffeine ingestion on cycling time trial (TT) performance in well trained male subjects. METHODS: Eight males, with the following physical characteristics (Mean +/- SD) age 30.2+/-10.1 years, height 180.3+/-7.1 cm, mass 70.4+/-5.1 kg, VO2max 63.6+/-4.4 mL.kg(-1).min(-1) undertook three 1 h TT performances on a VelotronPro cycle ergometer, in a double blind, random fashion. The trials were Control (C), Placebo (Pl) and Caffeine (CAF). The CAF and Pl were given 60 min prior to exercise in a dose of 6 mg.kg(-1) body mass. Prior to ingestion, 60 min post ingestion, and at the end of the TT, subjects gave 10 mL of venous blood which was analysed for lactate, glucose, and free fatty acids. Expired air was collected throughout each test by indirect calorimetry. RESULTS: The cyclists rode significantly further in CAF trial (28.11+/-1.32 km) than they did in the C (26.69+/-1.5 km, P < 0.03) or Pl (27.0+/-1.5 km, P < 0.03) trials. No significant differences were seen between C and Pl trials (P > 0.88). No differences between C and Pl were seen in heart rate data throughout the TT (p > 0.05). The free fatty acid (FFA) concentrations were significantly higher in the CAF trials both post ingestion (P < 0.005) and post exercise (P < 0.0001) than either C or Pl trials. CONCLUSION: We concluded that performance was improved possibly based upon a greater reliance on fat metabolism, as indicated by increased FFA and a lower respiratory exchange ratio (RER).

Time at or near VO2max during continuous and intermittent running. A review with special reference to considerations for the optimisation of training protocols to elicit the longest time at or near VO2max.

Several authors have suggested that training at or near VO2max (i.e. > or = 95% VO2max) is the most effective training intensity to enhance VO2max and that for highly trained endurance athletes, training at or near VO2max may be necessary to increase it further. Consequently, there is an interest in characterising training protocols that allow the longest time at or near VO2max (T@VO2max). Intermittent running protocols have been found to be more effective than continuous protocols for increasing T@VO2max. Intermittent protocols can be manipulated by altering the warm-up intensity and timing, work and relief interval velocity and duration, amplitude, interval number per set, and the number of sets performed. To increase T@VO2max it is recommended that work interval intensity should generally range between 90% and 105% vVO2max and relief interval intensity between 50% vVO2max and the lactate threshold velocity. Work and relief interval durations should be between 15 and 30 seconds. The warm-up period prior to the intermittent protocol should be about 10 to 15 minutes in duration at 1 or 2 km x h(-1) below the lactate threshold velocity, with no gap between the warm-up and the intermittent protocol. When designing intermittent training protocols for the enhancement of VO2max, the simultaneous enhancement of other physiological performance determinants should also be considered. Further experimental research is required to identify the specific physiological responses and adaptations to various intermittent running protocols that are designed to elicit the longest time at or near VO2max, before recommendations can be given to competitive endurance runners.

Criteria and other methodological considerations in the evaluation of time at V.O2max.

AIM: Many previous studies have examined the time limit at which an individual can maintain VO(2max) (T(lim) VO(2max)) during high-intensity continuous and intermittent runs to exhaustion. The main purpose of the present study was to examine the effects of employing different criteria used in previous investigations during T(lim) VO(2max) evaluation. METHODS: Seven moderately trained competitive runners completed 2 running tests to exhaustion, during which metabolic data was obtained from breath-by-breath gas analysis. The 1(st) test was an incremental test to evaluate VO(2max) and the minimal running velocity at which VO(2max) was elicited (v VO(2max)). The 2(nd) test was a continuous single velocity test at v VO(2max) from which the time to attain VO(2max) (TA VO(2max)) and T(lim) VO(2max) were subsequently evaluated. Time at VO(2max) was evaluated employing 6 specific criteria. Intra-individual differences in T(lim) VO(2max) values due to applying the different criteria were analysed using a one-way ANOVA, with significant differences between pairs identified using Tukey's HSD posthoc test. Significance was set at p<0.05. RESULTS: A one-way ANOVA demonstrated that significant differences (F=4.03, p=0.005) existed between T(lim) VO(2max) values generated by employing the six different criteria. CONCLUSIONS: The present study provides support that employing different criteria in the evaluation of T(lim) VO(2max), such as those used in previous investigations, leads to significantly different T(lim) VO(2max) values. However, the practical implications of these measurement differences require further investigation.

Influence of exercise modality on agreement between gas exchange and heart rate variability thresholds.

The main purpose of this study was to investigate the level of agreement between the gas exchange threshold (GET) and heart rate variability threshold (HRVT) during maximal cardiopulmonary exercise testing (CPET) using three different exercise modalities. A further aim was to establish whether there was a 1:1 relationship between the percentage heart rate reserve (%HRR) and percentage oxygen uptake reserve (%VO2 R) at intensities corresponding to GET and HRVT. Sixteen apparently healthy men 17 to 28 years of age performed three maximal CPETs (cycling, walking, and running). Mean heart rate and VO2 at GET and HRVT were 16 bpm (P<0.001) and 5.2 mL · kg(-1) · min(-1) (P=0.001) higher in running than cycling, but no significant differences were observed between running and walking, or cycling and walking (P>0.05). There was a strong relationship between GET and HRVT, with R2 ranging from 0.69 to 0.90. A 1:1 relationship between %HRR and % VO2 R was not observed at GET and HRVT. The %HRR was higher during cycling (GET mean difference=7%; HRVT mean difference=11%; both P<0.001), walking (GET mean difference=13%; HRVT mean difference=13%; both P<0.001), or running (GET mean difference=11%; HRVT mean difference=10%; both P<0.001). Therefore, using HRVT to prescribe aerobic exercise intensity appears to be valid. However, to assume a 1:1 relationship between %HRR and % VO2 R at HRVT would probably result in overestimation of the energy expenditure during the bout of exercise.

Influence of exercise modality on agreement between gas exchange and heart rate variability thresholds

The main purpose of this study was to investigate the level of agreement between the gas exchange threshold (GET) and heart rate variability threshold (HRVT) during maximal cardiopulmonary exercise testing (CPET) using three different exercise modalities. A further aim was to establish whether there was a 1:1 relationship between the percentage heart rate reserve (%HRR) and percentage oxygen uptake reserve ( % V ˙ O 2  R ) at intensities corresponding to GET and HRVT. Sixteen apparently healthy men 17 to 28 years of age performed three maximal CPETs (cycling, walking, and running). Mean heart rate and V ˙ O 2 at GET and HRVT were 16 bpm (P<0.001) and 5.2 mL·kg-1·min-1 (P=0.001) higher in running than cycling, but no significant differences were observed between running and walking, or cycling and walking (P>0.05). There was a strong relationship between GET and HRVT, with R2 ranging from 0.69 to 0.90. A 1:1 relationship between %HRR and % V ˙ O 2  R was not observed at GET and HRVT. The %HRR was higher during cycling (GET mean difference=7%; HRVT mean difference=11%; both P<0.001), walking (GET mean difference=13%; HRVT mean difference=13%; both P<0.001), or running (GET mean difference=11%; HRVT mean difference=10%; both P<0.001). Therefore, using HRVT to prescribe aerobic exercise intensity appears to be valid. However, to assume a 1:1 relationship between %HRR and % V ˙ O 2  R at HRVT would probably result in overestimation of the energy expenditure during the bout of exercise.

The effects of caffeine ingestion on time trial cycling performance.

PURPOSE: The purpose of this work was to determine the effects of caffeine on high intensity time trial (TT) cycling performance in well-trained subjects. SUBJECTS: Six male cyclists with the following physical characteristics (mean +/- SD) age 30.7 +/- 12, height 179.3 +/- 7.5 cm, mass 70.0 +/- 7.5 kg, VO2max 65.0 +/- 6.3 mL.kg-1.min-1 undertook three 1-h TT performances, control (C), placebo (P) and caffeine (CAF), on a Velotron cycle ergometer conducted in a double-blind, random fashion. Subjects rested for 60 min and were then given CAF or P in a dose of 6 mg.kg-1 body mass and then commenced exercise after another 60 min of rest. Before ingestion, 60 min postingestion, and at the end of the TT, finger-prick blood samples were analyzed for lactate. RESULTS: The cyclists rode significantly further in the CAF trial (28.0 +/- 1.3 km) than they did in the C (26.3 +/- 1.5 km, P < .01) or P (26.4 +/- 1.5 km, P < .02) trials. No differences were seen in heart rate data throughout the TT (P > .05). Blood lactate levels were significantly higher at the end of the trials than either at rest or postingestion (P < .0001), but there were no differences between the three trial groups. CONCLUSION: On the basis of the data, we concluded that performance was improved with the use of a caffeine supplement.

Pre-exercise alkalosis and acid-base recovery.

The aim of this study was to observe the influence of pre-exercise sodium bicarbonate (NaHCO3) ingestion and varying recovery modes on acid-base recovery from a single bout of supramaximal exercise. Nine male subjects completed four separate, randomized cycle ergometer exercise trials to volitional fatigue at 120% maximum power output, under the following conditions: 0.3 g.kg(-1) BW NaHCO3 ingestion with passive recovery (BICARB P), 0.3 g.kg (-1) BW NaHCO3 ingestion with active recovery (BICARB A), placebo ingestion with passive recovery (PLAC P) and placebo ingestion with active recovery (PLAC A). Capillary blood samples were obtained every minute for 15 min during recovery. Significant main effects for pH were observed for time (F = 42.1, p < 0.001), intervention (BICARB and PLAC) (F = 1117.3, p < 0.001) and recovery condition (F = 150.0, p < 0.001), as the BICARB condition reduced acid-base perturbation. Significant interaction effects were observed between conditions (BICARB and PLAC) for active and passive recovery modes (F = 29.1, p < 0.001) as the active recovery facilitated H+ removal better than the passive condition. Pre-exercise alkalosis attenuates blood acid-base perturbations from supramaximal exercise to exhaustion, regardless of whether the recovery mode is active or passive. These findings suggest that individuals may benefit from introducing a pre-exercise alkalotic condition while including passive recovery during high-intensity training protocols.

Reproducibility of time at or near VO2max during intermittent treadmill running.

The purpose of this study was to determine the reproducibility of time at or above 90 % (t (90 % )VO (2max)) and 95 % (t (95 % )VO (2max)) maximal oxygen uptake during an intermittent treadmill run to exhaustion. Twenty-two distance runners (age 38.0 +/- 7.1 yrs) performed two identical incremental and two identical intermittent tests on four separate days. Respiratory exchange was measured continuously throughout each test by an automated open-circuit gas analysis system. The incremental test consisted of increases in treadmill speed every minute until volitional exhaustion. The highest averaged 30-s oxygen uptake (VO (2)) value was defined as VO (2max) and the minimum speed that elicited VO (2max) was defined as vVO (2max). The intermittent test consisted of 30-s work intervals ran at 105 % vVO (2max) interspersed by 30-s relief intervals ran at 60 % vVO (2max) and was continued until volitional exhaustion. The time that VO (2) was at or above 90 % and 95 % of the mean maximum values elicited during the two previous incremental tests was determined for the intermittent tests. The mean t (95 % )VO (2max) was 232 (SD 174) s and 244 (SD 195) s and the mean t (90 % )VO (2max) was 480 (SD 220) s and 488 (SD 252) s, for trial 1 and trial 2, respectively. Reproducibility statistics for t (95 % )VO (2max) and t (90 % )VO (2max), respectively, were: 95 % limits of agreement 12 +/- 227 s and 8 +/- 328 s; coefficient of variation 34.5 % and 24.5 %; and intraclass correlation coefficient 0.80 and 0.75. Statistical power analysis indicated that this level of reproducibility would allow mean differences of 15 - 20 % between intermittent training protocols to attain statistical significance in future experimental research, with sample sizes probably within the resources of most researchers.

Physiological determinants of time to exhaustion during intermittent treadmill running at vV(.-)O(2max).

Previous studies have reported large between-subject variations in the time to exhaustion during intermittent running at the velocity at V(.-)O (2max) (vV(.-)O (2max)). This study aimed to determine which physiological factors contribute to this variability. Thirteen male runners (age 38.9 +/- 8.7 years) each completed five treadmill running tests; two incremental tests to determine V(.-)O (2max), vV(.-)O (2max), the lactate threshold velocity (vLT) and the running velocity--V(.-)O (2) relationship; the third test to determine the time to exhaustion during continuous running at vV(.-)O (2max) (t (lim)cont); the fourth to determine the maximal accumulated oxygen deficit (MAOD); the fifth to determine the time to exhaustion during intermittent running at vV(.-)O (2max) (t (lim)int). Relief intervals during the intermittent test were run at 70 % vV(.-)O (2max). The vLT-vV(.-)O (2max) difference was significantly correlated with t (lim)int (r = - 0.70; p = 0.007). The correlation coefficient increased to r = - 0.83 (p < 0.001) when the difference between the relief interval velocity and the vLT was deducted from the vLT-vV(.-)O (2max) difference (theoretically representing the net depletion of the MAOD during each work/relief interval cycle). The main finding of this study was that 49 % of the variance in t (lim)int was explained by the vLT-vV(.-)O (2max) difference, compared to 74 % for t (lim)cont. However, a further 20 % of unique variance in t (lim)int could be explained with the inclusion of the relief interval velocity-vLT difference. Theoretically, runners with the largest relief interval velocity-vLT difference will replete their anaerobic capacity to a greater extent during each relief interval, thereby increasing time to exhaustion.

Time at VO2max during intermittent treadmill running: test protocol dependent or methodological artefact?

Effects of methodological differences on the determination of time at VO (2max) (t (VO2max)) during intermittent treadmill running were investigated. Subjects performed three incremental tests to volitional exhaustion: a continuous protocol with 1-min stages (Cont-INC ([1-min])), and two discontinuous protocols of 2-min (Dis-INC ([2-min])) and 3-min (Dis-INC ([3-min])) stage durations. For each test, VO (2max) and the running velocity associated with V.O (2max) (vVO (2max)) were determined. On a fourth visit, subjects performed an intermittent test with 30-s work and relief intervals run at 105 % and 60 %, respectively, of the vV. (2max) determined during Cont-INC ((1-min)). The t (VO2max) during the intermittent test was determined using three different criteria: VO (2) data points > or = 100 % VO (2max) determined in Cont-INC ((1-min)) (t (VO2max[100 %])), > or = 95 % VO (2max) (t (VO2max[95 %])) and > or = VO (2max) minus 2.1 ml . kg (-1) . min (-1) (t (VO2max[- 2.1])). The V.O (2max) means (SD) for Cont-INC ((1-min)), Dis-INC ((2-min)) and Dis-INC ((3-min)) were 4093 (538), 4096 (516), and 3980 (488) mL . min (-1), respectively. The t (VO2max) means (SD) were: t (VO2max(100 %)) 163 (227) s, t (VO2max(95 %)) 418 (439) s, and t (VO2max(- 2.1)) 358 (395) s. All differences in t (V.O2max) were significantly different (p < 0.05). Differences in t (VO2max) due to using V.O (2max) values derived from using different V.O (2) time-averages were significantly different (p < 0.05). Methodological differences should be considered during interpretation of previous studies.

The relationship between the lactate turnpoint and the time at VO2max during a constant velocity run to exhaustion.

The present investigation examined the relationship between the running velocity at the lactate turnpoint (vLTP) and the time at which VO2max can be sustained (TVO2max) during a continuous run to exhaustion at the minimal running velocity that elicits VO2max (vVO2max). Seven moderately-trained endurance runners undertook three tests on a treadmill. The first test was to determine vVO2max; the second to determine the time to exhaustion during a constant velocity run at vVO2max (Tlim vVO2max) and TVO2max; and the third to determine the vLTP. Pearson's correlation coefficient was used to determine the association between the vLTP (%vVO2max; i.e. the relative vLTP) and TVO2max, and between other selected physiological variables. Correlations between the relative vLTP and TVO2max, expressed as a percentage of T(lim vVO2max (the relative TVO2max; r=0.82), and between TVO2max and Tlim vVO2max (r=0.89), were significant at the p<0.05 level. All other correlations between selected measured physiological variables were found to be statistically insignificant. The main finding of this present study is that the relative vLTP demonstrated a significant positive correlation with the relative TVO2max. The physiological mechanism by which the lactate turnpoint may influence the relative TVO2max has not been elucidated, but may be due to a combination of decreasing the time to attain VO2max and increasing Tlim vVO2max. The present investigation has demonstrated that the lactate turnpoint may influence the relative time at which VO2max can be sustained during a continuous run to exhaustion at vVO2max, although further research is required to substantiate these findings.