W. F. M. Wallace

Training effects of short bouts of stair climbing on cardiorespiratory fitness, blood lipids, and homocysteine in sedentary young women

Objectives: To study the training effects of eight weeks of stair climbing on Vo2max, blood lipids, and homocysteine in sedentary, but otherwise healthy young women. Methods: Fifteen women (mean (SD) age 18.8 (0.7) years) were randomly assigned to control (n  =  7) or stair climbing (n  =  8) groups. Stair climbing was progressively increased from one ascent a day in week 1 to five ascents a day in weeks 7 and 8. Training took place five days a week on a public access staircase (199 steps), at a stepping rate of 90 steps a minute. Each ascent took about two minutes to complete. Subjects agreed not to change their diet or lifestyle over the experimental period. Results: Relative to controls, the stair climbing group displayed a 17.1% increase in Vo2max and a 7.7% reduction in low density lipoprotein cholesterol (p<0.05) over the training period. No change occurred in total cholesterol, high density lipoprotein cholesterol, triglycerides, or homocysteine. Conclusions: The study confirms that accumulating short bouts of stair climbing activity throughout the day can favourably alter important cardiovascular risk factors in previously sedentary young women. Such exercise may be easily incorporated into the working day and therefore should be promoted by public health guidelines.

Effect of cold exposure of the rabbit on the subsequent performance of its isolated ear artery with respect to temperature

SummaryNew Zealand white rabbits were exposed to an environmental temperature of either 20°C (control) or 5°C (cold-exposure) for periods of from one to six weeks. Ear skin temperature was around 30°C in the control environment and fell to around 15°C in the cold environment. Compared with control arteries, ear arteries from cold-exposed animals tended to have a lower optimal temperature for responses to injected noradrenaline (NOR). At 37°C, responses of control arteries exceeded those of cold-exposed arteries; at 12°C the situation was reversed. A similar “cross-over” effect was observed with responses to electrical stimulation (ES). However, in both groups of arteries, responses to ES were better preserved than were responses to NOR at low temperatures, possibly because cooling interfered with uptake into neuronal stores of NOR released by ES, thus allowing more NOR to reach the arterial muscle at these low temperatures.New Zealand white rabbits were exposed to an environmental temperature of either 20°C (control) or 5°C (cold-exposure) for periods of from one to six weeks. Ear skin temperature was around 30°C in the control environment and fell to around 15°C in the cold environment. Compared with control arteries, ear arteries from cold-exposed animals tended to have a lower optimal temperature for responses to injected noradrenaline (NOR). At 37°C, responses of control arteries exceeded those of cold-exposed arteries; at 12°C the situation was reversed. A similar “cross-over” effect was observed with responses to electrical stimulation (ES). However, in both groups of arteries, responses to ES were better preserved than were responses to NOR at low temperatures, possibly because cooling interfered with uptake into neuronal stores of NOR released by ES, thus allowing more NOR to reach the arterial muscle at these low temperatures.

Anticholinesterases and the cholinergic link hypothesis with reference to the rabbit ear artery

1. Constrictor responses of the isolated perfused rabbit ear artery to electrical stimulation and to intraluminally applied noradrenaline and histamine have been studied before and after addition to the perfusate of the anticholinesterases neostigmine and physostigmine. 2. Both neostigmine (6×10−5−2.4×10−4 mol/l) and physostigmine (6×10−5mol/l) caused a small but significant (P<0.05) increase in responses to electrical stimulation and to intraluminal noradrenaline and histamine. The degree of potentiation was similar for all three modes of stimulation, suggesting that neostigmine and physostigmine act at smooth muscle level rather than at nerve terminal level. 3. In the presence of a high potassium perfusate, the artery failed to respond to electrical stimulation but still responded to noradrenaline and histamine. In this medium, the potentiating action of neostigmine disappeared, suggesting that this action depends on the initial presence of a normal resting membrane potential in the arterial smooth muscle cells. 4. These results do not support the cholinergic link hypothesis, that acetylcholine is involved in the release of noradrenaline at adrenergic nerve terminals.Summary1.Constrictor responses of the isolated perfused rabbit ear artery to electrical stimulation and to intraluminally applied noradrenaline and histamine have been studied before and after addition to the perfusate of the anticholinesterases neostigmine and physostigmine.2.Both neostigmine (6×10−5−2.4×10−4 mol/l) and physostigmine (6×10−5mol/l) caused a small but significant (P<0.05) increase in responses to electrical stimulation and to intraluminal noradrenaline and histamine. The degree of potentiation was similar for all three modes of stimulation, suggesting that neostigmine and physostigmine act at smooth muscle level rather than at nerve terminal level.3.In the presence of a high potassium perfusate, the artery failed to respond to electrical stimulation but still responded to noradrenaline and histamine. In this medium, the potentiating action of neostigmine disappeared, suggesting that this action depends on the initial presence of a normal resting membrane potential in the arterial smooth muscle cells.4.These results do not support the cholinergic link hypothesis, that acetylcholine is involved in the release of noradrenaline at adrenergic nerve terminals.

Training effects of short bouts of stairclimbing in sedentary young women

One strategy advocated to meet the current physical activity guidelines is to accumulate activity in short bouts throughout the day. The efficacy of this approach has been demonstrated experimentally using 10-minute bouts of activity; however, it remains unclear whether accumulating very short bouts of exercise lasting approximately 2 minutes can also confer health benefits. PURPOSE: To investigate the training effects of eight weeks of stairclimbing on VO2max, blood lipids and homocysteine in sedentary, but otherwise healthy young women. METHODS: Fifteen women, aged 18.8 ± 0.7 yrs (mean ± SD), were randomly assigned to control (n = 7) or stairclimbing (n = 8) groups. Stairclimbing was progressively increased from one ascent per day in week 1 to five ascents per day in weeks 7 and 8. Training took place 5 d wk-1, on a public access staircase (199 steps), at a stepping rate of 90 steps min-1. Each ascent took approximately 2 minutes to complete. Subjects agreed not to change their diet or lifestyle over the experimental period. RESULTS: Relative to controls, the stairclimbing group displayed an increase in VO2max (+4.5 ± 3.7 mL·kg·min-1, p < 0.05) and a reduction in LDL-C (-0.17 ± 0.27 mmol·L-1, p < 0.05) over the training period. No change occurred in total cholesterol, HDL-C, triglycerides or homocysteine. CONCLUSION: These findings indicate that accumulating short bouts of stairclimbing activity throughout the day can favourably alter important cardiovascular risk factors in previously sedentary young women.

Evidence for a species-specific relationship between the amount of smooth muscle relative to lumen size and the sensitivity to noradrenaline of muscular arteries of the rabbit, ox, sheep and pig

SummaryThe ratio of the area of the smooth muscle coat to lumen area (MA/LA) has been measured in cross-sections of rabbit, ox, sheep and pig ear artery, rabbit femoral and small mesenteric arteries of the ox and sheep.A linear relationship was established between log MA/LA and log dose noradrenaline required to cause a standard pressure rise in the perfused artery. Results for ear and mesenteric or femoral arteries from the same species lay on the same line, but arteries from different species lay on different lines.