The use of the CR-10 scale to allow self-regulation of isometric exercise intensity in pre-hypertensive and hypertensive participants.

PURPOSE: Isometric exercise (IE) has been shown to lower blood pressure (BP). Using equipment with force output displays, intensity is usually regulated at 30% maximal voluntary contraction (MVC); however, the cost of programmable equipment and their requirement for maximal contractions presents limitations. A simple, cost-effective alternative deserves investigation. The purpose of this study was (1) to explore the relationship between %MVC, change in systolic BP (ΔSBP), and perceived exertion (CR-10) and (2) to assess the validity of self-regulation of intensity during isometric hand-grip exercise. METHODS: Fourteen pre-hypertensive and hypertensive adults completed eight, 2-min isometric hand-grip exercises at randomised intensities; participants estimated their perceived exertion at 30-s intervals (estimation task). Subsequently, on three separate occasions, participants performed four 2-min contractions at an exertion level that they perceived to be equivalent to CR-10 "Level-6" (production task). RESULTS: There were significant linear relationships between the estimated exertion on the CR-10 scale, and ΔSBP (r = 0.784) and %MVC (r = 0.845). Level-6 was equivalent to an average ΔSBP of 38 mmHg (95% CI; 44, 32 mmHg) and a relative force of 33% MVC (95% CI; 36.2, 30%). During the production task, %MVC was not significantly different between the estimation task and each production trial. In at least the first two repetitions of each production trial, ΔSBP was significantly lower than that observed in the estimation task. CONCLUSION: These findings show that CR-10 "Level-6" is an appropriate method of self-regulating isometric hand-grip intensity; its use offers an affordable and accessible alternative for isometric exercise prescription aimed at reducing BP.

Exploring the performance reserve: Effect of different magnitudes of power output deception on 4,000 m cycling time-trial performance.

PURPOSE: The aim of the present study was to investigate whether a magnitude of deception of 5% in power output would lead to a greater reduction in the amount of time taken for participants to complete a 4000 m cycling TT than a magnitude of deception of 2% in power output, which we have previously shown can lead to a small change in 4000 m cycling TT performance. METHODS: Ten trained male cyclists completed four, 4000 m cycling TTs. The first served as a habituation and the second as a baseline for future trials. During trials three and four participants raced against a pacer which was set, in a randomized order, at a mean power output equal to 2% (+2% TT) or 5% (+5% TT) higher than their baseline performance. However participants were misled into believing that the power output of the pacer was an accurate representation of their baseline performance on both occasions. Cardiorespiratory responses were recorded throughout each TT, and used to estimate energy contribution from aerobic and anaerobic metabolism. RESULTS: Participants were able to finish the +2% TT in a significantly shorter duration than at baseline (p = 0.01), with the difference in performance likely attributable to a greater anaerobic contribution to total power output (p = 0.06). There was no difference in performance between the +5% TT and +2% TT or baseline trials. CONCLUSIONS: Results suggest that a performance reserve is conserved, involving anaerobic energy contribution, which can be utilised given a belief that the exercise will be sustainable however there is an upper limit to how much deception can be tolerated. These findings have implications for performance enhancement in athletes and for our understanding of the nature of fatigue during high-intensity exercise.

Reproducibility of 24-h ambulatory blood pressure and measures of autonomic function.

Determining the number of familiarization sessions required for accurate recordings of ambulatory blood pressure monitoring and autonomic function is a prerequisite for the appropriate design of intervention studies. The benefit of familiarization trials remains largely unexplored. The objective of the current investigation was to assess the reproducibility of 24-h ambulatory blood pressure, 24-h heart rate variability (HRV) and resting measurements of HRV and blood pressure variability (BPV). Eleven prehypertensive and hypertensive adults participated. Ambulatory blood pressure and HRV were measured across 24 h on four occasions. In addition, 5-min resting measures of HRV and BPV were recorded and analysed. Variability between consecutive pairs of trials was calculated. The typical error induced by ambulatory recordings of systolic blood pressure reduced over time (3.8-2.8 mmHg). The greatest effect of familiarization was observed at night. Ambulatory HRV was more reproducible than resting measures. The most reproducible markers were root mean square of successive differences [coefficient of variation (CV): 13.2-10%] and high frequency normalized units (CV: 15.2-6.4%), with the percentage of adjacent NN intervals differing by more than 50 ms showing the poorest reproducibility (CV: 23.9-20.7%). Overall BPV (SD) was more reproducible than the frequency domain low frequency component. Familiarization trials are required for the most accurate recordings of both 24-h ambulatory blood pressure monitoring and HRV. Ambulatory HRV provide superior reproducibility to resting measurements.

Asymmetry of Cerebral Hemodynamic Response to Incremental Cycling Exercise.

PURPOSE: Exercise is known to result in hemodynamic changes in the bilateral prefrontal cortex. The aim of this study was to investigate hemodynamic changes in right and left hemispheres of the prefrontal cortex (PFC) during incremental cycling exercise. METHODS: After 10 min rest, 9 participants (mean age 26.6 ± 2.5 y, mass 77.5 ± 9.7 kg, stature 1.79 ± 0.9 m) cycled at 100-150 W for 4 min. Thereafter, resistance was increased by 25 W every 4 min until exhaustion (EXH). Respiratory exchange and concentrations of oxy- ([HbO2]), deoxy- ([(HHb]), and total hemoglobin ([Hb(tot)]) in the PFC were continuously measured. Data were averaged for 60 s at rest and preceding ventilatory threshold 1 (VT1), VT2, and volitional EXH and after 5 min recovery. Subjective ratings of affect were measured at VT1, VT2, VT1 minus 25 W (VT1-25W), and VT2 plus 25 W (VT2+25W). RESULTS: There were no between-hemispheres differences in [HbO2] or [Hb(tot)] at rest, VT1, or recovery or in [HHb] at any point. Right-hemisphere [HbO2] and [Hb(tot)] were significantly greater than left at VT2 (P = .01 and P = .02) and EXH (P = .03 and P = .02). Affect was significantly greater at VT1-25W vs VT2 and VT2+25W and at VT1 and VT2 vs VT2+25W (P < .01-.03). CONCLUSIONS: To the authors' knowledge, this is the first study to describe an exercise-state-dependent change in PFC asymmetry during incremental exercise. The asymmetry detected coincided with a decrease in affect scores in agreement with the PFC-asymmetry hypothesis.

Reproducibility of pacing strategy during simulated 20-km cycling time trials in well-trained cyclists.

The aim of the study was to assess the reproducibility of pacing strategy, physiological and perceptual responses during simulated 20-km cycling time trials. Seventeen well-trained male cyclists ([Formula: see text] = 4.70 ± 0.33 L min(-1)) completed three 20-km time trials on a Velotron Pro cycle ergometer within a maximum duration of 14 days. During all trials power output, cadence and respiratory exchange were recorded throughout, rating of perceived exertion and affective response were recorded every 2-km and capillary blood was sampled and assayed for the determination of lactate concentration every 4-km. Power output data was assigned to 1-km 'bins' and expressed relative to the mean to quantify pacing strategy. Reproducibility of the pacing strategy and the whole trial mean responses was subsequently quantified using typical error (TE) with 90% confidence intervals. The pacing strategy adopted was similar across repeat trials, though there was a higher degree of variability at the start and end of the trial (TE = 6.6 and 6.8% for the first and last 1-km), and a trend for a progressively blunted start on repeat trials. The reproducibility of performance, cardiorespiratory and perceptual measures was good (TE range 1.0-4.0%), but blood lactate exhibited higher variability (TE = 17.7%). The results demonstrate the performance, perceptual and physiological response to self-paced 20-km time trials is reproducible in well-trained cyclists. Future research should acknowledge that variability in pacing strategy at the start and end of a self-paced bout is likely regardless of any intervention employed.

The effect of self- even- and variable-pacing strategies on the physiological and perceptual response to cycling.

It has been proposed that an even-pacing strategy is optimal for events lasting <120 s, but this assertion is not well-established. This study tested the hypothesis that even-paced cycling is less challenging than self- or variable-paced cycling. Ten well-trained male cyclists (VO2max, 4.89 ± 0.32 L min(-1)) completed a self-paced (SP) 20-km time trial followed by time- and work-matched even-paced (EP 100% SP mean power) and variable-paced (VP 142 and 72% SP mean power, 1:1.5 high:low power ratio) trials in a random, counterbalanced order. During all trials expired air and heart rate were analysed throughout, blood lactate was sampled every 4 km, and perceptual responses (rating of perceived exertion (RPE) and affect) were assessed every 2 km and post-trial. There were no whole trial statistically significant differences between trials for any of the respiratory variables measured, although there was a trend for higher RER's in VP compared to EP (P = 0.053). Blood lactate was lower in EP compared to VP (P = 0.001) and SP (P = 0.001), and higher in SP compared to VP (P = 0.008). RPE was lower, and affect more positive, in EP compared to both SP and VP (P > 0.05). The results of this study show that, for a time- and work-matched 20-km time trial, an even-paced strategy results in attenuated perturbations in the physiological response and lower perception of effort in comparison to self- and variable-paced strategies.

Consistency of perceptual and metabolic responses to a laboratory-based simulated 4,000-m cycling time trial.

Although pacing-related research is widely reported, no studies have described the consistency of pacing strategies or their associated energetic contributions. This study aimed to investigate the consistency of pacing and energetic outlay by establishing the typical within and between trial variations during simulated 4,000 m time trials. Fifteen well-trained male cyclists performed three, 4,000 m time trials with 3-7 days separating each trial. Power output, cadence, heart rate, respiratory exchange and iEMG of the vastus lateralis were recorded continuously throughout each trial. To examine within-trial variability, the data were assigned to 10% bins. Rating of perceived exertion and affective response were recorded every 400 m and a capillary blood sample was collected and assayed for blood lactate concentration every 800 m. Mean typical error across trials 1-3 for all variables was low (range 2.1-6.3%) and lower between trials 2-3 for all variables with the exception of cadence. There were no between-trial differences in pacing strategy; however, typical error for each 10% bin was lower between trials 2-3 than trials 1-2. Anaerobic contribution to power was greatest during the first and last 10% of each trial (p > 0.05). In conclusion, well-trained cyclists demonstrated a high degree of consistency in terms of the pacing strategy they adopted which coincided with similar levels of energy distribution and perceived exertion. A laboratory simulated 4-km cycling trial is a reliable test that may be used to monitor performance and pacing strategy.