Ian Swaine

The effects of caffeine ingestion on performance time, speed and power during a laboratory-based 1 km cycling time-trial

Abstract There is little published data in relation to the effects of caffeine upon cycling performance, speed and power in trained cyclists, especially during cycling of ∼60 s duration. To address this, eight trained cyclists performed a 1 km time-trial on an electronically braked cycle ergometer under three conditions: after ingestion of 5 mg · kg−1 caffeine, after ingestion of a placebo, or a control condition. The three time-trials were performed in a randomized order and performance time, mean speed, mean power and peak power were determined. Caffeine ingestion resulted in improved performance time (caffeine vs. placebo vs. control: 71.1 ± 2.0 vs. 73.4 ± 2.3 vs. 73.3 ± 2.7 s; P = 0.02; mean ± s). This change represented a 3.1% (95% confidence interval: 0.7–5.6) improvement compared with the placebo condition. Mean speed was also higher in the caffeine than placebo and control conditions (caffeine vs. placebo vs. control: 50.7 ± 1.4 vs. 49.1 ± 1.5 vs. 49.2 ± 1.7 km · h−1; P = 0.0005). Mean power increased after caffeine ingestion (caffeine vs. placebo vs. control: 523 ± 43 vs. 505 ± 46 vs. 504 ± 38 W; P = 0.007). Peak power also increased from 864 ± 107 W (placebo) and 830 ± 87 W (control) to 940 ± 83 W after caffeine ingestion (P = 0.027). These results provide support for previous research that found improved performance after caffeine ingestion during short-duration high-intensity exercise. The magnitude of the improvements observed in our study could be due to our use of sport-specific ergometry, a tablet form and trained participants.

Effect of isometric exercise on resting blood pressure: a meta analysis

Dynamic physical exercise (walking, swimming, and so on) is an important component of lifestyle changes to reduce blood pressure; however, many individuals are unwilling or unable to adopt this lifestyle change. Isometric exercise has not traditionally been recommended as an alternative to dynamic exercise and has not been well studied. A meta-analysis of controlled trials of isometric exercise on resting blood pressure was therefore undertaken. Five trials were identified including a total of 122 subjects. Isometric exercise for <1 h per week reduced systolic blood pressure by 10.4 mm Hg and diastolic blood pressure by 6.7 mm Hg. These changes are similar to those achieved with a single pharmacological agent. These results suggest that isometric exercise may be of value as part of lifestyle advice in maintaining a desirable blood pressure.

Arm and leg power output in swimmers during simulated swimming

PURPOSE Previously, it has not been possible to compare power output of the arms and legs during simulated swimming using dry-land ergometry. The purpose of this study was to determine arm-pulling and leg-kicking power using isokinetic dry-land ergometry. METHODS Twenty-two highly trained male swimmers of mean (+/- SD) age, 23 +/- 3.6 yr; body mass, 78 +/- 5.9 kg; and stature, 1.79 +/- 0.04 m were recruited to the study. First, subjects performed 10 s of all-out exercise at each of five resistance settings, with 1 h rest in between, to determine the best maximal pull velocity (MPVopt). Second, they performed an all-out 30-s test at MPVopt, which was repeated the following day. These repeated 30-s tests were performed separately using simulated front-crawl arm-pulling and leg-kicking, on a computer-interfaced swim bench and purpose-built leg-kicking ergometer. Peak and mean power output (PPO; MPO) were determined from regression analysis of the power vs time relationship. RESULTS The mean (+/- SEM) PPO for arms and legs were 304 +/- 22 W versus 435 +/- 36 W. For MPO, the means were 225 +/- 31 W vs 312 +/- 26 W, respectively. These values were attained at mean MPVopt of 2.5 +/- 0.2 m x s(-l) for arms and 2.3 +/- 0.4 m x s(-1) for legs. The variation in PPO from repeated testing was 7.3% for arms and 8.3% for legs. CONCLUSIONS These results show that the legs can sustain greater power output than the arms during simulated swimming. Also, the intra-subject variation in measurement of power output is small using these dry-land ergometers. These methods of assessment might be useful in explaining swimming performance and in monitoring changes that take place during training.

Effects of the Intensity of Leg Isometric Training on the Vasculature of Trained and Untrained Limbs and Resting Blood Pressure in Middle-Aged Men

The purpose of this study was to establish whether changes in resting blood pressure and the vasculature of trained and untrained limbs are dependent on training intensity, following isometric-leg training. Thirty middle-aged males undertook an 8 week training programme (4 × 2 min bilateral-leg isometric contractions 3 times per week). Two groups trained at either high (HI; 14%MVC) or low (LO; 8%MVC) intensity a third group (CON) acted as controls. All parameters were measured at baseline, 4-weeks and post-training. Resting SBP (−10.8 ± 7.9 mmHg), MAP (−4.7 ± 6.8 mmHg) and HR (−4.8 ± 5.9 b·min−1) fell significantly in the HI group post-training with concomitant significant increases in resting femoral mean artery diameter (FMAD; 1.0 ± 0.4 mm), femoral mean blood velocity (FMBV; 0.68 ± 0.83 cm·s−1), resting femoral artery blood flow (FABF; 82.06 ± 31.92 ml·min−1) and resting femoral vascular conductance (FVC, 45%). No significant changes occurred in any brachial artery measure nor in any parameters measured in the LO or CON groups. These findings show that training-induced reductions in resting blood pressure after isometric-leg training in healthy middle-aged men are associated with concomitant adaptations in the local vasculature, that appear to be dependent on training intensity and take place in the later stages of training.

Effects of a 15-week accumulated brisk walking programme on the body composition of primary school children.

Abstract The purpose of this study was to establish whether an accumulated brisk walking programme, performed during the school day, is effective in changing body composition in primary school children aged 5–11 years. Altogether, 152 participants (79 boys and 73 girls) took part in this repeated-measures intervention study, divided into groups of walkers and controls. The walkers took part in the intervention during school time, which involved brisk walking around the school grounds for 15 min in the morning and afternoon, at least three times a week for 15 weeks. This represented an additional 90 min of moderate physical activity per week. The controls undertook their usual school day activities. Pre- and post-intervention anthropometric and body composition measures were taken. Body fat (−1.95 ± 2.6%) and fat mass (−0.49 ± 1.0 kg) were significantly reduced in the walkers after the intervention, whereas the controls showed no significant changes in these measures. Our results show that regular accumulated bouts of brisk walking during the school day can positively affect body composition in primary school children.

Markers of isometric training intensity and reductions in resting blood pressure

Abstract In this study, we examined the correlations between selected markers of isometric training intensity and subsequent reductions in resting blood pressure. Thirteen participants performed a discontinuous incremental isometric exercise test to volitional exhaustion at which point mean torque for the final 2-min stage (2min-torquepeak) and peak heart rate peak (HRpeak) were identified. Also, during 4 weeks of training (3 sessions per week, comprising 4 × 2 min bilateral leg isometric exercise at 95% HRpeak), heart rate (HRtrain), torque (Torquetrain), and changes in EMG amplitude (ΔEMGamp) and frequency (ΔEMGfreq) were determined. The markers of training intensity were: Torquetrain relative to the 2min-torquepeak (%2min-torquepeak), EMG relative to EMGpeak (%EMGpeak), HRtrain ΔEMGamp, ΔEMGfreq, and %MVC. Mean systolic (−4.9 mmHg) and arterial blood pressure (−2.7mmHg) reductions correlated with %2min-torquepeak (r = −0.65, P = 0.02 and r = −0.59, P = 0.03), ΔEMGamp (r = 0.66, P = 0.01 and r = 0.59, P = 0.03), ΔEMGfreq (r = −0.67, P = 0.01 and r = −0.64, P = 0.02), and %EMGpeak (systolic blood pressure only; r = −0.63, P = 0.02). These markers best reflect the association between isometric training intensity and reduction in resting blood pressure observed after bilateral leg isometric exercise training.

The effects of breathing 5% CO2 on human cardiovascular responses and tolerance to orthostatic stress

Breathing carbon dioxide (CO2) is known to induce hypercapnic acidosis and to affect chemoreceptor regulation of the cardiovascular system. However, there is limited information in the literature regarding the effects of breathing CO2 upon tolerance to orthostatic stress where cardiovascular regulation is challenged. The purpose of this study was to investigate the effect of breathing 5% CO2 on presyncopal tolerance to lower body negative pressure (LBNP). Nine subjects (five males and four females; average ±s.d. age 21.9 ± 0.9 years, height 172.4 ± 9.7 cm, mass 70.3 ± 7.1 kg) volunteered to participate in this study. Orthostatic tolerance was determined by exposing subjects to LBNP until the onset of presyncopal signs and symptoms on two occasions each separated by approximately 1 week. On one occasion investigations were carried out while subjects were breathing room air and on the other while subjects were breathing air containing 5% CO2, inducing hypercapnia and stimulating systemic chemoreceptors. During hypercapnic conditions, as compared with normocapnia, there were significant increases (P < 0.05) in minute ventilation, end‐tidal CO2 and estimated arterial PCO2. Furthermore, under hypercapnic conditions there was an increase in orthostatic tolerance, peak heart rate and time to peak heart rate during LBNP. The LBNP‐induced increase in calf circumference was significantly attenuated at −50 mmHg of LBNP in addition to a further 22.3% reduction in stroke volume under hypercapnic conditions. In conclusion, these results suggest that the possible protective element of presyncope was delayed during hypercapnia at the expense of further reductions in stroke volume. This delayed presyncopal response may have been associated with increases in cerebral blood flow (CBF) induced by the increased arterial PCO2.

The relationships between exercise intensity, heart rate, and blood pressure during an incremental isometric exercise test

Abstract Currently, it is not possible to prescribe isometric exercise at an intensity that corresponds to given heart rates or systolic blood pressures. This might be useful in optimizing the effects of isometric exercise training. Therefore, the aim of this study was to explore the relationships between isometric exercise intensity and both heart rate and systolic blood pressure during repeated incremental isometric exercise tests. Fifteen participants performed seated isometric double-leg knee extension, during which maximum voluntary contraction (MVC) was assessed, using an isokinetic dynamometer. From this, a corresponding peak electromyographic activity (EMGpeak) was determined. Subsequently, participants performed two incremental isometric exercise tests (at least 48 h apart) at 10, 15, 20, 25, and 30% EMGpeak, during which steady-state heart rate and systolic blood pressure were recorded. In all participants, there were linear relationships between %EMGpeak and heart rate (r at least 0.91; P < 0.05) and between %EMGpeak and systolic blood pressure (r at least 0.92; P < 0.05). Also, when repeated tests were compared, there were no differences in the slopes (P > 0.50) or elevations (P > 0.10) for either of the relationships. Therefore, these linear relationships could be used to identify isometric exercise training intensities that correspond to precise heart rates or systolic blood pressures. Training performed in this way might provide greater insight into the underlying mechanisms for the cardiovascular adaptations that are known to occur as a result.

Biomarkers of cardiovascular disease risk in 40–65-year-old men performing recommended levels of physical activity, compared with sedentary men

Objective: Both the UK Department of Health and the US Centers for Disease Control and Prevention have recommended at least 30 minutes of moderate-intensity physical activity on most days for health. Specific mention is made of beneficial effects upon blood lipids. The purpose of this study was to compare biomarkers of cardiovascular disease risk in men who perform physical activity in accordance with these recommendations with those who do not. Methods: 128 healthy men, aged 40–65 years, were recruited. 61 were classified as active (performing at least the minimum recommended physical activity of ⩾4 metabolic equivalents (METs), for 6 months immediately before the study) and 67 as sedentary. Fasting blood was drawn for total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), triglycerides, and apolipoproteins (Apo) A-1 and B. Low-density lipoprotein cholesterol (LDL-C) was estimated using the Friedewald equation. Results: The median (interquartile range) physical activity level was 7.0 (5.0–10.7) versus 1.0 (0–1.8) hour/week at ⩾4 METs (active versus sedentary; p<0.001). Apo A-1 was higher in the active men (p = 0.032). No significant differences were found for TC, HDL-C, LDL-C, TC:HDL-C, triglycerides, Apo B, or the Apo B:A-1 ratio. Conclusions: These findings suggest that physical activity performed according to the recommendations used in this study favourably influenced Apo A-1. The finding that cholesterol and triglycerides were not different in men achieving the recommended physical activity levels compared with sedentary men contradicts some of the claims made within the published recommendations. However, intervention studies are needed to clarify these preliminary findings.

Intensity-dependent reductions in resting blood pressure following short-term isometric exercise training

Abstract To reduce resting blood pressure, a minimum isometric exercise training (IET) intensity has been suggested, but this is not known for short-term IET programmes. We therefore compared the effects of moderate- and low-intensity IET programmes on resting blood pressure. Forty normotensive participants (22.3 ± 3.4 years; 69.5 ± 15.5 kg; 170.2 ± 8.7 cm) were randomly assigned to groups of differing training intensities [20%EMGpeak (~23%MVC, maximum voluntary contraction, or 30%EMGpeak (~34%MVC)] or control group; 3 weeks of IET at 30%EMGpeak resulted in significant reductions in resting mean arterial pressure (e.g. −3.9 ± 1.0 mmHg, P < 0.001), whereas 20%EMGpeak did not (−2.3 ± 2.9 mmHg; P > 0.05). Moreover, after pooling all female versus male participants, IET induced a 6.9-mmHg reduction in systolic blood pressure in female participants, but only a 1.5-mmHg reduction in systolic blood pressure in male participants, although the difference was not significant. An IET intensity between 20%EMGpeak and 30%EMGpeak is sufficient to elicit significant resting blood pressure reductions in a short-term training period (3 weeks). In addition, sexual dimorphism may exist in the magnitude of reductions, but further work is required to confirm this possibility, which could be important in understanding the mechanisms responsible.