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Biomedical subjects

T Reilly

Publications and source records attributed to T Reilly.

At least 145 records · Page 8Linked to original sources
PubMed1990

Running speed and spinal shrinkage in runners with and without low back pain.

Decreases in stature (shrinkage) are used to indicate exercise induced spinal loading. This study examined the effect of three running speeds on two groups of runners, one with chronic low back pain. The two groups of seven male marathon runners ran at 70%, 85%, and 100% of their marathon race pace for 30 min on separate occasions. Before and after exercise the subjects were seated for 20 min with the lumbar spine supported. Stature was measured before pre-exercise sitting, before running, after 15 min of running, after 30 min of running, and after post-exercise sitting. A stadiometer accurate to within 0.5 mm was used to record changes in stature. Results showed no differences in response to the three running regimens between the groups (P greater than 0.05). Shrinkage was greater during the first 15 min, being 3.26 (+/- 2.78) mm compared with 2.12 (+/- 1.61) mm for the second 15 min of the run (P less than 0.05). The faster the running speed the greater the resultant shrinkage. The 70%, 85%, and 100% conditions caused 3.37 (+/- 2.38), 5.10 (+/- 1.90), and 7.69 (+/- 3.69) mm of shrinkage, respectively (P less than 0.005). These results suggest that low back pain is independent of the shrinkage induced by running. Further research is required to determine the effect of longer duration runs on spinal shrinkage.

Adult↗
PubMed1990

Selective persistence of circadian rhythms in physiological responses to exercise.

An investigation along the circadian time scale in heart rate (HR), rectal temperature (Tr) and metabolic functions at rest, during submaximal and maximal exercise, and post-exercise was conducted using 15 male subjects. Each individual performed a cycle ergometer test on six separate days, temporally placed over the solar day to incorporate equidistant observation points. The exercise tests involved two consecutive 5-min loads at 82 and 147 W, then a graded increase of work-rate every 2 min to exhaustion. Significant circadian rhythms were evident at rest for HR, Tr, VO2 and VE, the HR acrophase at 13:50 hr leading that of the Tr and metabolic variables significantly (P less than or equal to 0.05). The circadian rhythms in metabolic measures were not evident at any exercise level or post-exercise and muscular efficiency was found to be independent of time of day. The exercise tolerance time and blood lactate post-exercise values failed to show a significant rhythm. In contrast the rhythms in HR and Tr were retained with similar phase and amplitude to those at rest during all work rates and post-exercise, though the amplitude of the HR cycle was attenuated at maximum.

Adult↗
PubMed1990

Human circadian rhythms and exercise.

Many biological functions change cyclically over a 24-h period, such cycles being referred to as circadian rhythms. The major rhythms of relevance to examine performance are those of body temperature and the sleep-wake cycle. Many components of exercise performance are closely related to the body temperature curve which peaks in the early evening. Exercise with predominantly neuromotor and cognitive components depend also on the underlying sleep-wake cycle. Some performance measures are subject to ultradian cycles and show a transient decline in the early afternoon. Optimal time of day for exercise is determined not just by endogenous rhythms but also by the nature and intensity of exercise, the population concerned, environmental conditions, and individual phase types. Environmental factors impinging on circadian rhythms include light, heat, air ionization, activity and eating patterns, and social activities. Endogenous rhythms are desynchronized when perturbed by nocturnal shift work or time-zone transitions. Coping with desynchronosis involves behavioral, dietary, or pharmacological treatments. Sleep loss interacts with circadian rhythmicity but affects cognitive function more so than gross motor actions. The existence of self-sustaining rhythms should be recognized by athletic practitioners, sports scientists concerned with experimental work and fitness testing, sports injury specialists, and sports organizers concerned with the travel plans of athletes.

Body Temperature Regulation↗
PubMed1990

Changes in stature following drop jumping and post-exercise gravity inversion.

Spinal shrinkage, measured by changes in stature, is used as an index of spinal loading as alterations reflect changes in intervertebral disc height. Shrinkage induced by various physical activities may be reversed using gravity inversion. The present purpose was to examine the shrinkage induced by a drop jumping regimen and evaluate gravity inversion post-exercise. Eight males, aged 20-31, performed two separate experimental protocols, each on different dates at 1400 h. Subjects stood for 30 min before undertaking an exercise regimen, consisting of five sets of five drop jumps from a height of 1 m, rebounding over a hurdle 0.5 m high. For 20 min, directly following the exercise regimen, subjects on one occasion stood and on a second occasion undertook gravity inversion. Shrinkage was monitored for 40 min after this post-exercise treatment. The stadiometer used to measure shrinkage was accurate to 0.05 mm. The exercise regimen caused a mean shrinkage of 1.68 and 1.81 mm for the two testing sessions. Post-exercise inversion and standing for 20 min increased stature by 5.18 and 0.76 mm, respectively (P less than 0.01). The 40-min standing period following inversion caused a rapid loss in stature (4.07 mm). At 30 min into this recovery period, there was no significant difference in shrinkage for either of the regimens. Results suggest that effects of an inversion treatment are short-lasting.

Adult↗
PubMed1990

Physiological strain unique to field hockey.

Unique requirements of field hockey include dribbling the ball and moving quickly in a semi-crouched posture. First, the net physiological strain due to dribbling was examined. Seven male hockey players completed a 5 min run on the treadmill at 8 km h-1 and 10 km h-1: subjects also ran at these speeds whilst dribbling a hockey ball. Dribbling increased energy expenditure by 15-16 kJ min-1 above that observed in normal running. Heart rates and perceived exertion were also increased. The posture in dribbling is likely to cause back ache among players: 53% of respondents (n = 81) reported experience of lower back pain. Finally, the shrinkage of spinal length during dribbling was examined. Subjects (n = 7) ran for 7 min on the treadmill whilst dribbling a ball. Shrinkage occurred at a rate of 0.4 mm min-1, which is greater than previously reported for other activities. The peculiar postural requirements of field hockey seem to cause physiological strain and spinal loading in excess of orthodox motion.

Adult↗
PubMed1989

Exercise-induced activation of the branched-chain 2-oxo acid dehydrogenase in human muscle.

The present study was conducted to investigate the metabolic regulation of the oxidation of branched-chain amino acids (BCAA) by exercise in human skeletal muscle. Five trained male volunteers were exercised on a cycle ergometer at 70% +/- 10% (mean +/- SD) of their maximal oxygen consumption (VO2max). Percutaneous quadriceps muscle biopsies were obtained under local anaesthesia at rest and after 30 and 120 min of exercise. In the muscle samples the active and total amount of the branched-chain 2-oxo acid dehydrogenase complex (BC-complex), the regulatory enzyme in the oxidative pathway of the BCAA, were measured. Glycogen content and activity of mitochondrial marker enzymes were also measured. Blood samples were obtained every 20 min for the measurement of metabolites. Heart rate and rated perceived exertion on the Borg scale were recorded every 10 min. At rest 4.0% +/- 2.5% of the BC complex was active, after 30 min of exercise 9.9% +/- 9.0% and after 120 min 17.5% +/- 8.5% (mean +/- SD). Exercise did not change the total activity. The largest activation was seen in two of the subjects who developed higher blood lactates early on during exercise and decreased their muscle glycogen more (indications of anaerobic metabolism). These data demonstrate that in trained individuals significant increases in the activity of the BC-complex occur only after prolonged intense exercise. In spite of the 4-fold activation, the data support the classical view that amino acids and protein do not contribute substantially as an energy source during exercise, since VO2 increased more than 20-fold.

3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)↗
PubMed1988

Iron, copper and zinc concentrations in human sweat and plasma; the effect of exercise.

The effect of 30 or 40 min hard exercise on a cycle ergometer upon plasma concentrations of zinc, iron and copper in twelve healthy male athletes was studied. Sweat samples were also collected from different body sites and analyzed for these metals. The metal content of sweat from different body sites varied, as did the sweating rates of different subjects. Pre-exercise plasma iron concentrations in 10 of the 12 subjects were within the normal range, but at least 4 subjects had sub-normal plasma zinc whereas six had plasma copper levels above normal. The effects of exercise on plasma metal concentrations varied from subject to subject; no general conclusions could be drawn about the biological significance of loss of metals in sweat in relation to whole body metal metabolism. It is suggested that a mild acute phase response may account for lowered zinc and raised copper in the plasma of athletes.

Adult↗
PubMed1987

Assessment of workload from measurements of stature.

The height of the body in the erect position varies by about 1% during the course of the day. It decreases rapidly after getting up and, depending on the pattern of work and rest, continues to reduce during the day; then overnight, it recovers. These changes result from changes in the height of the intervertebral discs. With conventional methods of measuring stature, these changes would go unrecognised. Apparatus has therefore been developed, allowing measurement to an accuracy of at least 1 mm. Studies have been made of static loading, dynamic lifting, running, in different types of seating and in resting postures. In general, height losses are proportional to the magnitude of lumbosacral compression, to the perception of exertion during physical exercise and to the levels of postural discomfort. Gains in height in positions of rest are proportional to the ratings for relaxation and comfort. For the ergonomist, therefore, the method offers a reliable means of assessing the effects on the spine of both physical work and rest-pauses.

Journal Article↗
PubMed1987

Prediction of lactate threshold and fixed blood lactate concentrations from 3200-m running performance in male runners.

To determine the effectiveness of a 3200-m time trial for predicting VO2 and running velocity at lactate threshold (LT), fixed blood lactate concentrations of 2.0, 2.5, and 4.0 mM, and peak, 42 male runners (means age = 31.1 +/- 8.3 years; means ht = 176.8 +/- 6.6 cm; means wt = 70.4 +/- 10.0 kg) completed a VO2 peak/LT test and a 3200-m time trial. The continuous treadmill protocol started at 0% grade 150 m/min and increased 10 m/min every 3 min until exhaustion. Velocity at LT, 2.0, 2.5, and 4.0 mM was determined from individual velocity blood lactate relationships, and VO2 values were determined from individual plots ov VO2 vs velocity. VO2 peak and velocity peak were chosen as the highest values observed. Oxygen uptake at LT, 2.0, 2.5, 4.0 mM, and peak was 52.51, 56.61, 58.31, 61.70, and 64.21 ml/kg.min-1, respectively, while the velocities associated with LT, 2.0, 2.5, 4.0 mM, and peak were 235.5, 251.5, 259.8, 273.5, and 285.5 m/min, respectively. During the 3200-m time trial (means time = 11.28 +/- 0.96 min), 400-m split times and cumulative times were recorded. Twenty-nine subjects were randomly assigned to a validation sample and the remaining subjects were used for cross-validation purposes. Regression analysis revealed that a 3200-m time trial was a good predictor of both VO2 (ml/kg.min-1) and velocity (m/min) at LT, 2.0, 2.5, 4.0 mM, and peak.

Adult↗