Alastair N. H. Hodges

Cerebrovascular responses to altitude.

The regulation of cerebral blood flow (CBF) is a complex process that is altered significantly with altitude exposure. Acute exposure produces a marked increase in CBF, in proportion to the severity of the hypoxia and mitigated by hyperventilation-induced hypocapnia when CO(2) is uncontrolled. A number of mediators contribute to the hypoxia-induced cerebral vasodilation, including adenosine, potassium channels, substance P, prostaglandins, and NO. Upon acclimatization to altitude, CBF returns towards normal sea-level values in subsequent days and weeks, mediated by a progressive increase in PO2, first through hyperventilation followed by erythropoiesis. With long-term altitude exposure, a number of mechanisms play a role in regulating CBF, including acid-base balance, hematological modifications, and angiogenesis. Finally, several cerebrovascular disorders are associated with altitude exposure. Existing gaps in our knowledge of CBF and altitude, and areas of future investigation include effects of longer exposures, intermittent hypoxia, and gender differences in the CBF responses to altitude.

The performance of the ice hockey slap and wrist shots: the effects of stick construction and player skill

The purpose of this study was to examine the interaction of players’ skill level, body strength, and sticks of various construction and stiffness on the performance of the slap and wrist shots in ice hockey. Twenty male and twenty female subjects were tested. Ten of each gender group were considered skilled and ten unskilled. In addition to general strength tests, each subject performed the slap and wrist shots with three stick shafts of different construction and stiffness. Shot mechanics were evaluated by simultaneously recording ground reaction forces from a force plate, stick movement and bending from high speed filming and peak puck velocity from a radar gun. Data were analysed with a 4-way repeated measures ANOVA for several dependent variables including peak puck velocity, peak Z (vertical) force, peak bending and stick to ground angles, peak angular deflection of the shaft, and hand placement on the stick. The results indicated that: 1) the slap shot was much faster than the wrist shot corresponding to greater vertical loading force, stick bending, and greater width of the hand placement; 2) the puck velocity was influenced by skill level and body strength but not stick type; and, 3) that skilled players were able to generate more vertical force and bend of the stick, in part, by adjusting their hand positions on the stick. Further studies are needed to address the specific influence of body strength and skill on the techniques of these shots and in relation to stick material and construction properties.

Effects of pseudoephedrine on maximal cycling power and submaximal cycling efficiency.

PURPOSE To study the effects of a therapeutic dose of pseudoephedrine on anaerobic cycling power and aerobic cycling efficiency. METHODS Eleven healthy moderately trained males (VO (2peak) 4.4 +/- 0.8 L x min(-1) participated in a double-blinded crossover design. Subjects underwent baseline (B) tests for anaerobic (Wingate test) and aerobic (VO (2peak) test) cycling power. Subjects ingested either 60 mg of pseudoephedrine hydrochloride (D) or a placebo (P) and, after 90 min of rest, a Wingate and a cycling efficiency test were performed. During the cycling efficiency test, heart rate (HR) and VO(2) were averaged for the last 5 min of a 10-min cycle at 40% and 60% of the peak power achieved during the VO (2peak) test. RESULTS There were no significant differences in peak power (B = 860 +/- 154, D = 926 +/- 124, P = 908 +/- 118 W), total work (B = 20 +/- 3, D = 21 +/- 3, P = 21 +/- 3 kJ), or fatigue index (B = 39 +/- 8, D = 45 +/- 5, P = 43 +/- 5%). There were no significant differences in HR at 40% power (D = 138 +/- 10, P = 137 +/- 10 beats.min-1) or 60% power (D = 161 +/- 11, P = 160 +/- 11 beats x min(-1). There were no significant differences in cycling efficiency at 40% power (D = 18.8 +/- 1.8, P = 18.5 +/- 1.8%) or 60% power (D = 20.3 +/- 2.0, P = 20.1 +/- 2.1%). CONCLUSION A therapeutic dose of pseudoephedrine hydrochloride does not affect anaerobic cycling performance or aerobic cycling efficiency.

Pulmonary Oedema following Exercise in Humans

Pulmonary physiologists have documented many transient changes in the lung and the respiratory system during and following exercise, including the incomplete oxygen saturation of arterial blood in some subjects, possibly due to transient pulmonary oedema. The large increase in pulmonary arterial pressure during exercise, leading to either increased pulmonary capillary leakage and/or pulmonary capillary stress failure, is likely to be responsible for any increase in extravascular lung water during exercise.The purpose of this article is to summarise the studies to date that have specifically examined lung water following exercise. A limited number of studies have been completed with the specific purpose of identifying pulmonary oedema following exercise or a similar intervention. Of these, approximately 50% have observed a positive change and the remaining have provided results that are either inconclusive or show no change in extravascular lung water.While it is difficult to draw a firm conclusion from these studies, we believe that pulmonary oedema does occur in some humans following exercise. As such, this is a phenomenon of significance to pulmonary and exercise physiologists. This possibility warrants further study in the area with more precise measurement tools than has previously been undertaken.

The Effects of 10 Weeks of Reforestation Work on Body Composition

Abstract Objective.—To document changes in body composition and body mass in male and female tree planters. Methods.—Height, mass, skin-fold thickness, and limb girths were measured in 17 male and 5 female tree planters before and after 10 weeks of work. Results.—Significant decreases were found in body mass (80.6 ± 10.7 kg vs 76.8 ± 8.5 kg) and body fat (13.3% ± 5.5% vs. 10.4% ± 5.0%) in the men (P < .05). No changes in skin-fold–corrected limb girths were found in the men or women. Initial body mass was significantly (P < .05) correlated with mass loss in men (r2 = .46) and women (r2 = .67). Estimated daily energy consumption was 20680.1 ± 2204.5 kJ for men and 14516.6 ± 2077.3 kJ for women, and estimated daily fat consumption was 194.2 ± 30.1 g for men and 132.3 ± 35.6 g for women. Conclusions.— Ten weeks of tree planting leads to significant decreases in body mass and body fat in men while maintaining skin-fold–corrected limb girths.

Effects of inhaled bronchodilators and corticosteroids on exercise induced arterial hypoxaemia in trained male athletes

Objectives: To determine the effect of prophylactic treatment with an inhaled bronchodilator and anti-inflammatory on arterial saturation (Sao2) in trained non-asthmatic male athletes with exercise induced arterial hypoxaemia (EIAH). Methods: Nine male athletes (mean (SD) age 26.3 (6.7) years, height 182.6 (7.9) cm, weight 79.3 (10.5) kg, Vo2max 62.3 (6.3) ml/kg/min, Sao2min 92.5 (1.1)%) with no history of asthma were tested in two experimental conditions. A combination of a therapeutic dose of salbutamol and fluticasone or an inert placebo was administered in a randomised crossover design for seven days before maximal cycling exercise. Oxygen consumption (Vo2), ventilation (Ve), heart rate (HR), power output, and Sao2 were monitored during the exercise tests. Results: There were no significant differences between the drug (D) and placebo (P) conditions for minimal Sao2 (D  =  93.6 (1.4), P  =  93.0 (1.1)%; p  =  0.93) Vo2max (D  =  61.5 (7.2), P  =  61.9 (6.3) ml/kg/min; p  =  0.91), peak power (D  =  444.4 (48.3), P  =  449.4 (43.9) W; p  =  0.90), peak Ve (D  =  147.8 (19.1), P  =  149.2 (15.5) litres/min; p  =  0.82), or peak heart rate (D  =  182.3 (10.0), P  =  180.8 (5.5) beats/min; p  =  0.76). Conclusions: A therapeutic dose of salbutamol and fluticasone did not attenuate EIAH during maximal cycling in a group of trained male non-asthmatic athletes.

One session of interval work does not alter VO2max, peak power or plasma volume

Abstract We examined the effect of one high-intensity cycling workout on aerobic capacity (VO2max), peak cycling power, and estimated change in plasma volume on subsequent days. Eight healthy males (age=29.5±5.3 years, height=1.81±0.09 m, mass=81.5±7.5 kg) visited the laboratory on three occasions. The first visit (D1) included baseline measures of cycling VO2max, haematocrit, and haemoglobin. Following a brief rest, the participants performed a high-intensity cycling workout of six 30-s cycling intervals (modelled on the Wingate cycle test) with each repetition separated by 3 min rest. The final two visits (D2 and D3) included identical measures as the first visit and occurred 48 and 96 h after the interval workout. No significant differences were found for VO2max (53.4±5.3, 53.7±6.7, and 53.7±6.2 ml · kg−1 · min−1), peak power (386±35, 384±35, and 389±35 W) or estimated change in plasma volume [−0.8±8.5% (D1–D2), 1.5±11.5% (D2–D3), and −1.6±9.6% (D1–D3)] between any of the three test days. Our results show that one short-term high-intensity cycling workout does not alter VO2max, peak power or estimated change in plasma volume on subsequent days, and is therefore unlikely to benefit or hinder performance.

Physical exertion and working efficiency of reforestation workers

BackgroundThe purpose of this study was to quantify the physical exertion during tree planting work and to examine the relationships between exertion, task efficiency, and productivity.MethodsHeart rate (HR) was monitored on 34 tree planters while they worked. HR data was collected for a complete working day on 19 subjects and for shorter periods of time on 15 subjects. Video of work tasks was recorded on 22 subjects (video was recorded on 7 of the subjects for whom HR was monitored through a full working day) and analyzed for working pace and proportion of time spent on each task.ResultsHR during a full day (9.0 ± 1.2 hours) of tree planting work was 115.2 ± 8.8 beats.min-1, and working HR was 128.2 ± 15.6 beats.min-1 for 82.5 ± 6.8% of the work day. Mean work pace was 452 ± 174 trees.h-1, and the proportion of time spent planting each tree was 53 ± 8% of the working time. Significant (P < 0.05) positive correlations were found between work pace and experience level, and between work pace and working HR, and a significant (P < 0.05) negative correlation was found between experience level and HR for a given work pace. No significant relationships were found between experience level or work pace and the proportion of time spent planting each tree.ConclusionsTree planters work at approximately 65% of age-predicted HRmax, and maintain HR at approximately 59% of HRmax throughout the entire working day. Productivity in these workers appears to be related to effort rather than to experience or task efficiency per se.

Field versus race pace conditions to provoke exercise-induced bronchoconstriction in elite swimmers: Influence of training background

Background Diagnosing Airway hyper-responsiveness (AHR) requires bronchial provocation tests that are performed at rest and after exercise or hyperventilation in either a lab or field setting. Presently, it is unclear whether the proposed AHR field test for swimming induces sufficient provocation due to lack of intensity. Thus we aimed to examine how the 8 minute field swim test compared to all out racing and a lower intensity practice exposure affected AHR. We hypothesized that the race would affect AHR the most thereby highlighting the importance of maximal effort in swim AHR. Methods 10 female and 15 male swimmers completed three conditions (sanctioned race of different distances, 8 min field swim challenge and swim practice). Forced vital capacity (FVC), forced expired volume in 1 second (FEV1) and forced expiratory flow (FEF25-75) were measured at rest and after each exercise condition (at 6 and 10 min) in accordance with standard protocols. AHR was defined as a decrease in FEV1 of ≥10% post exercise. Results A significant increase in FEV1 and FEF25-75 was observed for both post swim field test and post-race. The practice condition reduced FEV1 in 44% of swimmers although the magnitude of change was small. There was a wide variability in the individual responses to the 3 conditions and AHR was diagnosed in one swimmer (race condition). Conclusion All conditions have poor sensitivity to diagnose EIB and total accumulated ventilation (distance swum) did not influence AHR. These results also indicate that elite swimmers, despite many risk factors, are not limited by respiratory function in race conditions. It is proposed that the swim field test not be used for AHR assessment in swimmers due to too high relative humidity.

The effects of a delay following warm-up on the heart rate response to sudden strenuous exercise.

Introduction: Sudden strenuous exercise (SSE) has previously been shown to result in electrocardiograph (ECG) abnormalities indicative of myocardial ischemia when not preceded by a warm-up. Athletes regularly undergo SSE and are often unable to warm-up immediately prior to competition. It is unknown whether a delay post warm-up will result in the same heart rate (HR) response to SSE as seen with no warm-up. Aims: To compare the HR response and to observe for ECG abnormalities during SSE with a warm up, with a delay after warm up and without a warm up. Methods: Seven male subjects randomly completed three SSE exercise conditions while being monitored by ECG; a 15 second supramaximal sprint following three conditions: no warm up (NW); Original Research Article Lesser and Hodges; BJMMR, 8(9): 765-771, 2015; Article no.BJMMR.2015.504 766 immediately following a warm-up (WU); and following a 10-minute delay post warm up (D). There were no ECG abnormalities across any of the conditions indicative of myocardial ischemia. Results: Significant differences (p<0.05) were found in the HR response for all time periods during exercise between WU and NW, between WU and D, but not between D and NW. A delay between warm-up and SSE resulted in a lowered HR response to the SSE compared with a warm-up immediately preceding, but a higher HR response to SSE with no warm-up. Conclusion: The findings of this study suggest that a 10 minute delay following warm-up before SSE is too long to maintain the benefits of warm-up.