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Biomedical subjects

T Reilly

Publications and source records attributed to T Reilly.

At least 73 records · Page 4Linked to original sources
PubMed1999

Effects of moderate dietary manipulations on swim performance and on blood lactate-swimming velocity curves.

Blood lactate responses are commonly employed for evaluation and prescription of training programmes. The purpose of the present studies was to examine the effects of dietary manipulations on both swim performance and on the relationship between blood lactate and swimming velocity. The first study engaged 8 subjects in a regimen to reduce muscle glycogen by a combination of diet and training. Subjects were monitored under a normal mixed diet comprising 53.6+/-7.8% carbohydrate (CHO) and under a decreased CHO condition (39.4+/-10.7% CHO) over 3 days. Mean swim performance decreased significantly (P<0.05) over 400 yards as a result of the carbohydrate reduction regimen. Mean blood lactates were reduced as a consequence of the glycogen depletion regimen following swims at 85% and 100% of maximum velocities. The swimming velocity corresponding to 4 mM blood lactate (V-4 mM) was altered from 0.67+/-0.04 m x s(-1) on a mixed diet to 0.70+/-0.05 m x s(-1) on a CHO-reduced diet. The second study employed 7 subjects in a regimen to enhance muscle glycogen stores. Subjects were monitored over 3 days under a normal diet (52.7+/-4.4% CHO) and on a separate occasion under an increased CHO intake (59.2+/-3.7% CHO). In contrast to the first study, mean swim performance improved over 100 yards and 400 yards (P<0.05). Mean blood lactates were evaluated after the carbohydrate-rich regimen at both 85% and 100% swim velocities (P<0.05). The mean swim velocity associated with V-4mM was paradoxically reduced from 0.69+/-0.05 to 0.67+/-0.04 m x s(-1) as a result of the increased CHO condition. The results indicate that a moderate reduction in CHO intake alters swimming performance adversely whereas a moderate elevation in CHO intake above the normal diet improves performance. The dietary manipulations affected the response of blood lactate to both submaximal and maximal swimming velocities. The observations highlight the limitations of applying lactate response curves to swim training.

Adolescent↗
PubMed1999

Activation and disturbance of blood haemostasis following strenuous physical exercise.

Physical exercise activates blood coagulation and enhances fibrinolytic activity. To investigate whether these activations of blood coagulation and fibrinolysis are balanced post-exercise and during the period of recovery, 11 moderately active young men were examined immediately after a standardised cycle ergometer test and during the 24 h period of recovery. Blood samples were obtained at rest, immediately after exercise, and 2, 6 and 24 h after exercise. All post-exercise values were corrected for any change in plasma volume. Exercise induced a significant increase in factor VIII activity and this occurred with a significant shortening of activated partial thromboplastin time. A concomitant enhancement of tissue plasminogen activity resulted in significant increases in tissue plasminogen activity antigen and total fibrin/fibrinogen degradation products, and a significant decrease in tissue plasminogen activator inhibitor-1 activity. Increases in coagulation and fibrinolytic activity changed in parallel during exercise. However, during recovery, while the increase in factor VIII activity post-exercise persisted 2 and 6 h into recovery, fibrinolytic activity demonstrated a sharp fall. It is concluded that whereas the enhanced fibrinolytic activity during exercise appears to counterbalance the increase in blood coagulability, this haemostatic balance is not maintained during recovery. This perturbed blood haemostasis could constitute an enhanced risk for coronary artery thrombosis and may contribute to exercise-related cardiovascular events.

Adult↗
PubMed1999

Manual handling performance: the effects of menstrual cycle phase.

Physiological and subjective responses to physical performance have been shown to interrelate with fluctuations in the female hormonal environment throughout the menstrual cycle. The aim of this study was to examine whether these fluctuations affect the strenuous performance required in manual handling. Seventeen eumenorrheic females performed lifting tasks in five phases of their menstrual cycle. These tasks were maximal isometric lifting strength (MILS) and an endurance lift at 45% MILS (t), at both knee and waist height; and the selection of a maximal acceptable load (MAL) to lift six times per min, for 10 min, in both the sagittal and asymmetric planes. Heart rate response (HR) and rating of perceived exertion (RPE) were recorded throughout each of the lifting tasks. MILS, t and the chosen MAL were unaffected by menstrual phase over both heights and planes of lift (p > 0.05). HR to the isometric endurance lift was greater following ovulation than prior to ovulation by approximately 7 beats.min-1 (p < 0.05). This was true when the data were analysed at 50, 80 and 100% of the time to volitional fatigue, and by an area under the curve procedure. HR to the dynamic lifting tasks was also elevated by approximately 7 beats.min-1 following ovulation. This difference was non-significant due to the low power of the analysis. Re-analysis of the data by re-sampling 1000 matched comparisons produced significant phase variations (p < 0.05). The RPE for all of the lifting tasks was independent of menstrual phase (p > 0.05). The impact of the eumenorrheic menstrual cycle on lifting capability was negligible in the present study. However, the results of this study indicate that all further investigations utilizing HR data to produce recommendations for health and safety in manual handling tasks must control for menstrual cycle phase in female populations.

Adolescent↗
PubMed1999

Maximal physiological responses to deep and shallow water running.

The maximal physiological responses to treadmill running (TMR), shallow water running (SWR) and deep water running (DWR) while wearing a buoyancy vest were compared in 15 trained male runners. Measurements included oxygen consumption (VO2 max), respiratory exchange ratio (RER) and heart rate (HR). Treadmill running elicited VO2 max and HRmax, which were higher than the peaks attained in both water tests (p < 0.01). VO2 peak averaged 83.7 and 75.3% of VO2 max for SWR and DWR respectively. Peak HR for SWR and DWR were 94.1 and 87.2% of the HRmax reached in the TMR. RER responses were similar between the three modalities. The observations suggest that the training stimulus provided by water is still adequate for supplementary training. While SWR is potentially an efficient method of maintaining cardiovascular fitness, it needs to be investigated further to establish if it is a viable technique for the injured athlete to employ.

Adult↗
PubMed1999

Monitoring the health status and impact of treatment on Americans: the Medicare Beneficiary Health Status Registry.

OBJECTIVE: A major new survey program, the Medicare Beneficiary Health Status Registry (MBHSR), has been proposed to improve the monitoring of the health status of Medicare beneficiaries. The MBHSR would collect data by mail with telephone follow up of nonrespondents to permit economical assessment of a total Registry of approximately 200,000 Medicare beneficiaries, approximately 54,000 of whom would be surveyed in any given year. (Surveys would be conducted of samples of new enrollees who would be reinterviewed every five years.) METHOD: To assess the feasibility of that approach, a field test was conducted with a probability sample (n = 1,922) that comprised approximately equal numbers of new Medicare enrollees (aged, 65) and current beneficiaries (age range, 76-80). The field test was designed to assess the quality of the data that this design would produce. FINDINGS: Results indicate that the proposed design of the MBHSR could achieve response rates of approximately 80% among both age cohorts using a survey instrument that took 30 minutes to complete. Internal reliability of Activities of Daily Living, Instrumental Activities of Daily Living, Mobility, Mental Health Index, General Health, and Prostate Symptomatology scales ranged from 0.77 to 0.93. When measurements were repeated approximately 30 days after the initial survey, moderate to high levels of cross temporal correlation (range, 0.64-0.96) were found for most indexes, with the exception of prostate symptomatology. In addition, an earlier comparison of survey responses in the MBHSR field test to Medicare payment records indicated that the MBHSR field test obtained highly accurate reports of most of the major surgeries that were recorded in Medicare claims files. CONCLUSION: The design proposed for the MBHSR is feasible. If implemented, it should produce acceptably high rates of response and data quality.

Activities of Daily Living↗
PubMed1999

Hormonal and metabolic responses to maintained hyperglycemia during prolonged exercise.

We studied the effects of maintained hyperglycemia (12 mmol/l) on endurance exercise to determine the hormonal and metabolic responses, the maximal rate of glucose infusion (i.e., utilization), and the effects on muscle glycogen stores. Eight men undertook two trials during which they exercised on a cycle ergometer at an intensity of approximately 70% peak O(2) uptake for 120 min. In the first trial (trial A), subjects had their blood glucose concentration clamped at 12 mmol/l 30 min before exercise and throughout exercise. The same rate and volume of infusion of saline as had occurred for trial A were used in a placebo trial (trial B). Maintained hyperglycemia resulted in significantly lowered plasma concentrations of nonesterified fatty acid, glycerol, 3-hydroxybutyrate, epinephrine, norepinephrine, and growth hormone (P < 0.001) during exercise, whereas concentrations of plasma insulin were significantly elevated (P < 0.001). Calculations of the rates of total carbohydrate oxidation showed that trial A resulted in significantly higher values when compared with trial B (P < 0.01) and that the maximal rates of glucose infusion varied between 1.33 and 2.78 g/min at 100-120 min. Muscle glycogen concentrations were significantly depleted (P < 0.01) after both trials (trial A, 170.3 micromol/g dry wt decrease; trial B, 206 micromol/g dry wt decrease), although this apparent difference may be accounted for by storage of 22.6 g glucose during the 30-min prime infusion. The results from this study confirm that maintained hyperglycemia attenuates the hormonal response and promotes carbohydrate oxidation and utilization and that muscle glycogen may not be spared.

3-Hydroxybutyric Acid↗
PubMed1999

Lack of evidence that feedback from lifestyle alters the amplitude of the circadian pacemaker in humans.

Two groups of healthy subjects were studied indoors, first while living normally for 8 days (control section) and then for 18 x 27 h "days" (experimental section). This schedule forces the endogenous (body clock-driven) and exogenous (lifestyle-driven) components of circadian rhythms to run independently. Rectal temperature and wrist movement were measured throughout and used as markers of the amplitude of the circadian rhythm, with the rectal temperature also "purified" by means of the activity record to give information about the endogenous oscillator. Results showed that, during the experimental days, there were changes in the amplitude of the overt temperature rhythm and in the relative amounts of out-of-bed and in-bed activity, both of which indicated an interaction between endogenous and exogenous components of the rhythm. However, the amplitude and the amount of overlap were not significantly different on the control days (when endogenous and exogenous components remained synchronized) and those experimental days when endogenous and exogenous components were only transiently synchronized; also, the amplitudes of purified temperature rhythms did not change significantly during the experimental days in spite of changes in the relationship between the endogenous and exogenous components. Neither result offers support for the view that the exogenous rhythm alters the amplitude of oscillation of the endogenous circadian oscillator in humans.

Activity Cycles↗
PubMed1999

Purification of masked temperature data from humans: some preliminary observations on a comparison of the use of an activity diary, wrist actimetry, and heart rate monitoring.

Fourteen ambulatory subjects, varying in their amount of habitual physical activity, were studied for 24 h during a total of 25 "typical" days. Rectal temperature was recorded every 6 minutes, an activity diary was filled in every half hour, and wrist activity and heart rate were monitored every minute. Actimetry and heart rate data generally showed close parallelism with each other and with the masking effects on body temperature. Psychological stressors such as public speaking produced a greater effect on heart rate and body temperature than on wrist movement, while typing produced high values for wrist movement, but affected heart rate and temperature much less. When data for the circadian rhythm of body temperature were purified, the diary, actimetry, and measurement of heart rate were all useful in reducing masking effects, but the present evidence indicates that heart rate can be more successful than actimetry--as judged by the closeness of the purified data to a sinusoid. This superiority of heart rate monitoring over wrist activity as a method of purification might be because core temperature can be increased by stressor-induced thermogenesis, as well as by physical activity, and because wrist movement can, with some activities, give an inaccurate estimate of the factors that contribute to whole-body thermogenesis.

Adult↗
PubMed1999

The effect of activity on the waking temperature rhythm in humans.

Nine healthy female subjects were studied when exposed to the natural light-dark cycle, but living for 17 "days" on a 27h day (9h sleep, 18h wake). Since the circadian endogenous oscillator cannot entrain to this imposed period, forced desynchronization between the sleep/activity cycle and the endogenous circadian temperature rhythm took place. This enabled the effects of activity on core temperature to be assessed at different endogenous circadian phases and at different stages of the sleep/activity cycle. Rectal temperature was measured at 6-minute intervals, and the activity of the nondominant wrist was summed at 1-minute intervals. Each waking span was divided into overlapping 3h sections, and each section was submitted to linear regression analysis between the rectal temperatures and the total activity in the previous 30 minutes. From this analysis were obtained the gradient (of the change in rectal temperature produced by a unit change in activity) and the intercept (the rectal temperature predicted when activity was zero). The gradients were subjected to a two-factor analysis of variance (ANOVA) (circadian phase/ time awake). There was no significant effect of time awake, but circadian phase was highly significant statistically. Post hoc tests (Newman-Keuls) indicated that gradients around the temperature peak were significantly less than those around its trough. The intercepts formed a sinusoid that, for the group, showed a mesor (+/-SE) of 36.97 (+/-0.12) and amplitude (95% confidence interval) of 0.22 degrees C (0.12 degrees C, 0.32 degrees C). We conclude that this is a further method for removing masking effects from circadian temperature rhythm data in order to assess its endogenous component, a method that can be used when subjects are able to live normally. We suggest also that the decreased effect of activity on temperature when the endogenous circadian rhythm and activity are at their peak will reduce the possibility of hyperthermia.

Adolescent↗
PubMed1999

Changes in muscle strength in women following the menopause: a longitudinal assessment of the efficacy of hormone replacement therapy.

The effects of hormone deficiency at the menopause on muscle strength was examined in 10 healthy middle-aged women (1-3 years post-menopause) in a longitudinal trial over 39 weeks. Performance was compared with that of age-matched females (n=11) taking a course of hormone replacement therapy (HRT). Muscle strength of the quadriceps was measured isometrically at 90 degrees of knee flexion and at angular velocities of 1.05, 2.09 and 3.13 rad/s using an isokinetic dynamometer. Hand grip strength was assessed by means of a portable dynamometer. Measurements were taken every 13 weeks for 39 weeks. Significant decreases in isometric strength (-10%) and dynamic leg strength at 1.05 rad/s (-9%) were found in the post-menopausal women over 39 weeks. There was no change in strength in the HRT group. There were also no changes in leg strength at higher angular velocities or in grip strength for either the post-menopausal group or those taking HRT. While HRT preserved muscle strength, there was no evidence of a strengthening effect on skeletal muscle within this short period of treatment. A rapid loss of leg strength occurs post-menopausally in hormone-depleted women. HRT may offer protection against muscle weakness, although the hormone responsible for regulating strength is not evident using this model.

Exercise↗
PubMed1999

Investigation of anthropometric and work-rate profiles of Rugby Sevens players.

BACKGROUND: To describe anthropometric and match performance profiles of international Rugby Sevens players and explore correlations between anthropometric characteristics and work-rates in matches. METHODS: Profiles were compared by means of multivariate analysis and correlation techniques. SETTINGS: measurements were made on players participating in the 1996 International Rugby Sevens tournament in Uruguay. SUBJECTS: Thirty male players. MEASURES: work-rate analysis during matches (n = 30) and a comprehensive anthropometry profile of 27 of the 30 players. RESULTS: Forwards had more mass (whole-body, adipose tissue, muscle) than backs, jogged more frequently and paused more often. High intensity activity was negatively correlated with muscle mass and with mesomorphy. CONCLUSIONS: Anthropometric features are related to components of match play in Rugby Sevens but do not necessarily determine whether a game is won or lost.

Anthropometry↗
PubMed1998

Light of domestic intensity produces phase shifts of the circadian oscillator in humans.

Twelve subjects have been studied in a chamber that isolated them from external noise and lighting. After several control days, one group (n = 6) was subjected to 18 x 27-h 'days' and the other to 11 x 30-h 'days'. Sleep was in the dark, and awake times were spent in normal domestic lighting (150-500 lux). Rectal temperature and wrist actimetry were measured throughout, and the phase of the circadian oscillator was inferred from that of the temperature data, purified to remove direct effects of activity. During the experimental 'days' the rhythms showed a mean period of 24.4 h. A detailed examination of the phase shifts from one day to the next showed that small advances and delays were superimposed upon this drift. Moreover, the mean size and direction of these shifts depended upon the time of exposure to lighting relative to the temperature minimum, as would be predicted from a phase-response curve.

Adult↗
PubMed1998

Investigation of diurnal variation in sustained exercise performance.

Human performance generally varies in phase with the circadian curve in body temperature. This relationship between performance and core body temperature may be disrupted when exercise causes a pronounced rise in body temperature. In this study the authors compared responses to exercise in the morning and in the evening when pre-exercise body temperature differed significantly. Rectal temperature was measured pre-exercise and throughout a cycle ergometer test at 70% VO2 max in seven males (aged 19-24 years). The test was performed at 08:30 and 17:30 h, balanced for order with 3 days minimum between tests. Onset of sweating, weight loss and time to exhaustion were recorded. Metabolic measures (VO2, VE and RER) and heart rate were recorded pre-exercise and during exercise. Rectal temperature and skin temperature at three sites were also measured. Rectal temperature and heart rate were lower in the morning than in the evening by 0.6 degree C and 7 beats min-1 (p < 0.01), respectively. The lower body temperature in the morning persisted throughout exercise, the final rectal temperature being 38.6 (SD = 0.2) degrees C in the morning and 39.2 (SD = 0.5) degrees C in the evening. No effects of time of day were observed for VO2, VE, and RER but heart rate values during exercise were lower in the morning for 30 min (p < 0.05). Sweat onset occurred sooner at 08:30 h (7.57, SD = 0.90 min) compared to 17:30 h (8.71, SD = 2.20 min) (p < 0.05). Time to exhaustion ranged from 48 to 72 min, but did not vary with time of day (p > 0.05). It is concluded that continuous submaximal exercise is not necessarily disadvantaged by a morning timing.

Adaptation, Physiological↗
PubMed1998

Kinematics of running on 'off-road' terrain.

It has been established that running on natural 'off-road' terrain elicits a higher energy demand than running on road. Running on such terrain may also result in changes to the characteristics of the normal running stride. The aim of this study was to investigate biomechanical alterations to stride characteristics during off-road running. Nine female participants were recorded on video while running over three terrain types: surfaced footpath, short grass and long grass. The videos were digitized in order to quantify temporal, displacement and velocity variables. Cycle time was not significantly different between conditions (p = 0.315). Step length decreased (p < 0.01) and both vertical displacement of the hip and knee lift increased significantly (p < 0.01) with increasing difficulty of terrain. Despite assisted pacing, there was a significant decrease in velocity (p < 0.01) with each progressively rougher terrain condition. The peak extension angular velocity of the knee was not affected significantly (p < 0.098) by the terrain despite the fact that there was a significant difference in the peak flexion angular velocity (p < 0.01). It was concluded that participants altered their stride displacement and velocity patterns significantly in response to changes in running surface.

Adult↗
PubMed1998

Influence of acute endurance activity on leg neuromuscular and musculoskeletal performance.

PURPOSE: The purpose of this study was to investigate the effect of endurance activities designed to simulate the physiological demands of soccer match-play and training, on leg strength, electromechanical delay, and knee laxity. METHODS: Eight recreational soccer players completed four exercise trials in random order: 1) a prolonged intermittent high intensity shuttle run (PHISR) which required subjects to complete a total distance of 9600 m in a form simulating the pattern of physical activity in soccer match-play (activity mode; rest-to-work intervals; approximately 90 min duration), 2) a shuttle-run (SR), (3) a treadmill run (TR) which required subjects to complete an equivalent distance at a running speed corresponding to 70% VO2max, and 4) a control condition consisting of no exercise. RESULTS: Results from repeated measures ANOVA revealed significant condition (PHISR; SR; TR; control) by time (pre; mid; post) interactions for peak torque (PT: knee extension and flexion: 1.05 rad.s-1), EMD and anterior tibio-femoral displacement (TFD) (P < 0.05). Impairment to indices of knee joint performance was observed in PHISR, SR, and TR trials. The greatest decrement occurred in PHISR and SR trials (up to 44%). Knee extensor and flexor strength performance near to full knee extension (0.44 rad knee flexion) was not changed following the functionally-relevant endurance activities. CONCLUSIONS: Even though strength performance near to full knee extension was preserved following acute endurance activities, the risk of ligamentous injury may be increased by concomitant impairment to EMD and anterior TFD.

Adult↗