Stefanos Volianitis

Inspiratory muscle training improves rowing performance

PURPOSE To investigate the effects of a period of resistive inspiratory muscle training (IMT) upon rowing performance. METHODS Performance was appraised in 14 female competitive rowers at the commencement and after 11 wk of inspiratory muscle training on a rowing ergometer by using a 6-min all-out effort and a 5000-m trial. IMT consisted of 30 inspiratory efforts twice daily. Each effort required the subject to inspire against a resistance equivalent to 50% peak inspiratory mouth pressure (PImax) by using an inspiratory muscle training device. Seven of the rowers, who formed the placebo group, used the same device but performed 60 breaths once daily with an inspiratory resistance equivalent to 15% PImax. RESULTS The inspiratory muscle strength of the training group increased by 44 +/- 25 cm H2O (45.3 +/- 29.7%) compared with only 6 +/- 11 cm H2O (5.3 +/- 9.8%) of the placebo group (P < 0.05 within and between groups). The distance covered in the 6-min all-out effort increased by 3.5 +/- 1.2% in the training group compared with 1.6 +/- 1.0% in the placebo group (P < 0.05). The time in the 5000-m trial decreased by 36 +/- 9 s (3.1 +/- 0.8%) in the training group compared with only 11 +/- 8 s (0.9 +/- 0.6%) in the placebo group (P < 0.05). Furthermore, the resistance of the training group to inspiratory muscle fatigue after the 6-min all-out effort was improved from an 11.2 +/- 4.3% deficit in PImax to only 3.0 +/- 1.6% (P < 0.05) pre- and post-intervention, respectively. CONCLUSIONS IMT improves rowing performance on the 6-min all-out effort and the 5000-m trial.

Specific respiratory warm-up improves rowing performance and exertional dyspnea

PURPOSE The purpose of this study was a) to compare the effect of three different warm-up protocols upon rowing performance and perception of dyspnea, and b) to identify the functional significance of a respiratory warm-up. METHODS A group of well-trained club rowers (N = 14) performed a 6-min all-out rowing simulation (Concept II). We examined differences in mean power output and dyspnea measures (modified CR-Borg scale) under three different conditions: after a submaximal rowing warm-up (SWU), a specific rowing warm-up (RWU), and a specific rowing warm-up with the addition of a respiratory warm-up (RWUplus) protocol. RESULTS Mean power output during the 6-min all-out rowing effort increased by 1.2% after the RWUplus compared with that obtained after the RWU (P < 0.05) which, in turn, was by 3.2% higher than the performance after the SWU (P < 0.01). Similarly, after the RWUplus, dyspnea was 0.6 +/- 0.1 (P < 0.05) units of the Borg scale lower compared with the dyspnea after the RWU and 0.8 +/- 0.2 (P < 0.05) units lower than the dyspnea after the SWU. CONCLUSION These data suggest that a combination of a respiratory warm-up protocol together with a specific rowing warm-up is more effective than a specific rowing warm-up or a submaximal warm-up alone as a preparation for rowing performance.

The cerebral metabolic ratio is not affected by oxygen availability during maximal exercise in humans

Intense exercise decreases the cerebral metabolic ratio of O2 to carbohydrates (glucose +½ lactate) and the cerebral lactate uptake depends on its arterial concentration, but whether these variables are influenced by O2 availability is not known. In six males, maximal ergometer rowing increased the arterial lactate to 21.4 ± 0.8 mm (mean ±s.e.m.) and arterial–jugular venous (a–v) difference from −0.03 ± 0.01 mm at rest to 2.52 ± 0.03 mm (P < 0.05). Arterial glucose was raised to 8.5 ± 0.5 mm and its a–v difference increased from 1.03 ± 0.01 to 1.86 ± 0.02 mm (P < 0.05) in the immediate recovery. During exercise, the cerebral metabolic ratio decreased from 5.67 ± 0.52 at rest to 1.70 ± 0.23 (P < 0.05) and remained low in the early recovery. Arterial haemoglobin O2 saturation was 92.5 ± 0.2% during exercise with room air, and it reached 87.6 ± 1.0% and 98.9 ± 0.2% during exercise with an inspired O2 fraction of 0.17 and 0.30, respectively. Whilst the increase in a–v lactate difference was attenuated by manipulation of cerebral O2 availability, the cerebral metabolic ratio was not affected significantly. During maximal rowing, the cerebral metabolic ratio reaches the lowest value with no effect by a moderate change in the arterial O2 content. These findings suggest that intense whole body exercise is associated with marked imbalance in the cerebral metabolic substrate preferences independent of oxygen availability.

Cerebral oxygenation is reduced during hyperthermic exercise in humans

Aim:  Cerebral mitochondrial oxygen tension (PmitoO2) is elevated during moderate exercise, while it is reduced when exercise becomes strenuous, reflecting an elevated cerebral metabolic rate for oxygen (CMRO2) combined with hyperventilation‐induced attenuation of cerebral blood flow (CBF). Heat stress challenges exercise capacity as expressed by increased rating of perceived exertion (RPE).

Rowing, the ultimate challenge to the human body ― implications for physiological variables

Clinical diagnoses depend on a variety of physiological variables but the full range of these variables is seldom known. With the load placed on the human body during competitive rowing, the physiological range for several variables is illustrated. The extreme work produced during rowing is explained by the seated position and the associated ability to increase venous return and, thus, cardiac output. This review highlights experimental work on Olympic rowing that presents a unique challenge to the human capacities, including cerebral metabolism, to unprecedented limits, and provides a unique opportunity to reveal the extreme range of many physiological variables.

Plasma pH does not influence the cerebral metabolic ratio during maximal whole body exercise

Exercise is known to promote the use of lactate as metabolic fuel for the brain. As a result the cerebral metabolic ratio, an index of the brains metabolism, is reduced compared to rest. It is not known whether the exercise‐induced metabolic acidosis affects cerebral metabolism and the reduction of the cerebral metabolic ratio. We manipulated the metabolic acidosis by infusing bicarbonate in well trained rowers during a maximal rowing ergometer effort. We show that elimination of acidosis does not affect the reduction of the cerebral metabolic ratio. Furthermore, the data indicate that the capacity of the brain to take up lactate may have a limit. This indication requires further evaluation.

Baroreflex control of sinus node during dynamic exercise in humans: effect of muscle mechanoreflex

Aim:  This study evaluated the influence of muscle mechanical afferent stimulation on the integrated arterial baroreflex control of the sinus node during dynamic exercise.

The plasma atrial natriuretic peptide response to arm and leg exercise in humans: effect of posture

During arm exercise (A), mean arterial pressure (MAP) is higher than during leg exercise (L). We evaluated the effect of central blood volume on the MAP response to exercise by determining plasma atrial natriuretic peptide (ANP) during moderate upright and supine A, L and combined arm and leg exercise (A + L) in 11 male subjects. In the upright position, MAP was higher during A than at rest (102 ± 6 versus 89 ± 6 mmHg; mean ±s.d.) and during L (95 ± 7 mmHg; P < 0.05), but similar to that during A + L (100 ± 6 mmHg). There was no significant change in plasma ANP during A, while plasma ANP was higher during L and A + L (42.7 ± 12.2 and 43.3 ± 17.1 pg ml−1, respectively) than at rest (34.6 ± 14.3 pg ml−1, P < 0.001). In the supine position, MAP was also higher during A than at rest (100 ± 7 versus 86 ± 5 mmHg) and during L (92 ± 5 mmHg; P < 0.01) but similar to that during A + L (102 ± 6 mmHg). During supine A, plasma ANP was higher than at rest and during L but lower than during A + L (73.1 ± 22.5 versus 47.2 ± 15.9, 67.4 ± 18.3 and 78.1 ± 25.0 pg ml−1, respectively; P < 0.05). Thus, upright A was the exercise mode that did not enhance plasma ANP, suggesting that central blood volume did not increase. The results suggest that the similar blood pressure response to A and to A + L may relate to the enhanced central blood volume following the addition of leg to arm exercise.

Cardiovascular control during whole body exercise.

It has been considered whether during whole body exercise the increase in cardiac output is large enough to support skeletal muscle blood flow. This review addresses four lines of evidence for a flow limitation to skeletal muscles during whole body exercise. First, even though during exercise the blood flow achieved by the arms is lower than that achieved by the legs (∼160 vs. ∼385 ml·min(-1)·100 g(-1)), the muscle mass that can be perfused with such flow is limited by the capacity to increase cardiac output (42 l/min, highest recorded value). Secondly, activation of the exercise pressor reflex during fatiguing work with one muscle group limits flow to other muscle groups. Another line of evidence comes from evaluation of regional blood flow during exercise where there is a discrepancy between flow to a muscle group when it is working exclusively and when it works together with other muscles. Finally, regulation of peripheral resistance by sympathetic vasoconstriction in active muscles by the arterial baroreflex is critical for blood pressure regulation during exercise. Together, these findings indicate that during whole body exercise muscle blood flow is subordinate to the control of blood pressure.

The carotid baroreflex is reset following prolonged exercise in humans

Aim:  Alterations in the carotid baroreflex (CBR) control of arterial pressure may explain the reduction in arterial pressure and left ventricular (LV) function after prolonged exercise. We examined the CBR control of heart rate (HR) and mean arterial pressure (MAP), in addition to changes in LV function, pre‐ to post‐exercise.