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Biomedical subjects

A D Mahon

Publications and source records attributed to A D Mahon.

16 recordsLinked to original sources
PubMed2004

Running performance in middle-school runners.

AIM: This study examined the relationship of 3-km run time to indices of aerobic and anaerobic ability in 9 male runners (13.4+/-0.6 years, mean+/-SD). METHODS: Anthropometric measurements were made, and an exercise test to determine running economy at 187 m x min(-1) and (.-)VO(2max) were assessed on a treadmill. On a separate day, 2 55-m sprints followed by a 3-km run were performed on a 200-m indoor track. Capillary blood samples were obtained from a finger tip immediately after the run to determine blood lactate level. Fractional utilization (%(.-)VO(2max) used during the 3-km run) was calculated. Correlations were used to examine the relationship between run time and the physiological measurements. RESULTS: Mean values for (.-)VO(2), HR and RER at maximal exercise were 61.7+/-4.4 ml x kg(-1)xmin(-1), 198.9+/-6.7 b x min(-1), and 1.16+/-0.04, respectively. The average time to run 3 km was 13.27+/-0.97 min (90.1+/-7.2% of (.-)VO(2max)). Post-run blood lactate level was 8.3+/-3.2 mmol x L(-1) and was significantly related (r=-0.73, p=0.02) to 3-km time. Fractional utilization tended to be related (r=-0.56, p=0.12) to time. CONCLUSIONS: In this age group the ability to run at a high percentage of (.-)VO(2max) and tolerate a high blood lactate appear to be important determinants of running performance in young male runners.

Adolescent↗
PubMed2002

Attainment of maximal exercise criteria in boys and men.

BACKGROUND: This study tested the hypothesis that the occurrence of a VO(2) plateau at maximal exercise would be greater in men versus boys. Secondary indicators of maximal effort also were examined. METHODS: Sixteen boys (10.7+/-0.6 yrs) and 21 men (22.5+/-2.0 yrs) performed a graded exercise test on a treadmill at a constant speed of 8.04 km x hr(-1) with 2.5% increments in elevation. The men also performed a second test at 11.26 km x hr(-1) with similar increases in slope. RESULTS: At 8.04 km x hr(-1) , VO(2) max was 52.3+/-6.0 and 52.5+/-5.1 ml x kg(-1) x min(-1) in boys and men, respectively (p>0.05). In the men, VO(2) max (53.3+/-5.4 ml x kg(-1) x min(-1) ) was higher (p<0.05) in the faster protocol. The percentage of men achieving the criterion was nearly double the percentage of boys (23.8 vs 12.5%), although the difference was not significant. Age-specific criteria heart rate (HR) and respiratory exchange ratio (RER) were achieved in a similar manner; however, more men (100%) than boys (86.7%) achieved an age-specific blood lactate (BLa) criterion (p<0.05). Plateau achievement increased to 33.0% in the 11.26 km x hr(-1) protocol, but was not significantly different from 8.04 km x hr(-1). HR, RER and BLa criteria achievement were comparable. CONCLUSIONS: Maturation may influence the achievement of a plateau and BLa criteria, but not age-specific criteria for RER or HR.

Adult↗
PubMed2000

Cardiovascular responses during prolonged exercise at ventilatory threshold in boys and men.

PURPOSE: The purpose of this study was to examine the cardiovascular responses during prolonged exercise in boys and men at an intensity set relative to ventilatory threshold (VT). METHODS: Eight boys (10-13 yr) and 10 men (18-25 yr) completed an orientation trial, a maximal exercise test, and a 40-min submaximal exercise bout at an intensity equal to the VO2 at VT (approximately 64.5% VO2max). RESULTS: Heart rate (HR) was higher and stroke volume (SV) was lower in the boys compared with the men (P < or = 0.05). From 10 to 40 min, HR significantly increased 9.5% and 13.6% and SV significantly decreased 8.8% and 11.6% in the boys and men, respectively. Despite the tendency for the changes in HR and SV to be greater in the men, the group-by-time interaction was not significant. Cardiac output was greater in the men (P < or = 0.05) but remained constant over time (P > 0.05). In men, mean arterial blood pressure was higher (P < or = 0.05) and decreased 4.2% over time. In boys, mean arterial blood pressure remained constant, which resulted in a significant group-by-time interaction. Total peripheral resistance (TPR) was significantly higher in the boys and remained constant over time (P > 0.05). From 0 to 40 min, the decrease in plasma volume was significantly greater in the men (-10.2%) than the boys (-5.7%) but was unrelated to the changes in SV in either group (P > 0.05). CONCLUSION: In conclusion, the cardiovascular responses during prolonged exercise are similar in boys and men, although there is a tendency for the magnitude of cardiovascular drift to be greater in the men.

Adolescent↗
PubMed1998

Differentiated ratings of perceived exertion at ventilatory threshold in children and adults.

The purpose of this study was to examine overall, leg and chest ratings of perceived exertion (RPE) at ventilatory threshold (Thvent) in 16 children (mean age 10.9 years) and 17 adults (mean age 24.3 years). Thvent and maximum oxygen consumption (VO2max) were measured during a graded exercise test on a cycle ergometer. Overall, leg and chest RPE were obtained at the end of each exercise stage. VO2max was 49.9 (8.5) and 47.1 (6.1) ml x kg(-1) x min(-1) [mean (SD)] in the adults and children, respectively (P > 0.05). Relative to VO2max, Thvent was 61.7 (5.3)% in the adults and 64.7 (5.2)% in the children (P > 0.05). Overall, leg, and chest RPE values at Thvent for the adults were 11.5 (2.6), 11.9 (2.5), and 10.5 (2.5), while for the children these values were 13.6 (2.2), 14.1 (2.2), and 12.6 (2.3), respectively. All RPE values were higher for the children (P < 0.05). These results suggest that children are able to discriminate levels of exertion in different parts of their body during graded exercise. Furthermore, children rate an intensity corresponding to Thvent to require a greater overall, leg and chest effort than adults exercising at a similar intensity. This indicates that children experience more pronounced cardiorespiratory and muscular sensations during this type of exercise.

Adult↗
PubMed1998

Respiratory sinus arrhythmia during exercise in aerobically trained and untrained men.

Respiratory sinus arrhythmia (RSA) was examined in aerobically trained (AT) and untrained (NT) college-aged males during 12 periods consisting of a 3-min sitting baseline, six common 3-min absolute exercise stages, and five 3-min recovery stages that followed voluntary exhaustion to determine the relationship of work and training status to parasympathetic influence upon the heart. RSA systematically decreased during absolute exercise, was observed at heart rates (HR) above 100 beats x min(-1), and progressively increased during recovery. Additionally, independent of work stages, comparative regression analyses were conducted for both the exercise and recovery phases, separately, in which HR was regressed on RSA, as well as RSA on % VO2max, to contrast the obtained relationships for the AT and NT. No differences were revealed as a function of endurance training status as the slopes and intercepts obtained for the two groups from each of these analyses were similar. The within-subject correlations between RSA and % VO2max, calculated for each of the individuals across all 12 periods, were consistently negative. Between-subjects correlations of RSA with RR and tidal volume were predominantly nonsignificant, indicating that RSA, as measured here, is independent of individual differences in ventilatory activity and, as such, can be compared between groups during exercise. The findings demonstrate that RSA is detectable during both exercise and recovery, even at HR beyond 100 beats x min(-1), and reveals a similar relationship to HR and metabolic state in both aerobically trained and untrained populations.

Adult↗
PubMed1997

Blood lactate and perceived exertion relative to ventilatory threshold: boys versus men.

The purpose of this study was to examine blood lactate (BLa) levels and ratings of perceived exertion (RPE) in nine boys (10.5 +/- 0.7 yr) and nine men (25.3 +/- 2.0 yr) during exercise relative to ventilatory threshold (VT). VT and VO2max were determined during a graded exercise test on a cycle ergometer. On three additional days each subject exercised for 10 min at either 80, 100, or 120% of the VO2 at VT. Capillary BLa levels and RPE were assessed at minutes 5 and 10 of each trial. VO2max averaged 47.7 +/- 5.4 and 50.2 +/- 6.2 mL x g(-1) x min(-1) in the boys and men, respectively (P > 0.05). VT expressed as %VO2max was 67.2 +/- 3.5% in the boys and 67.3 +/- 4.9% in the men (P > 0.05). BLa levels ranged from 2.0 +/- 0.7 to 4.7 +/- 0.9 mmol x L(-1) in the boys and from 2.6 +/- 0.5 to 8.2 +/- 2.1 mmol x L(-1) in the men across the three intensities. Corresponding RPE values ranged from 11.2 +/- 1.8 to 16.2 +/- 2.2 in the boys and from 10.2 +/- 1.2 to 15.8 +/- 1.7 in the men. A group x time x intensity interaction (P < 0.05) indicated that BLa in the men increased more so across time and intensity. There were no significant group difference or interactions involving RPE during exercise. Setting exercise intensity relative to VT did not abolish child-adult differences with respect to submaximal BLa levels. Despite maintaining lower BLa levels, RPE values were similar between boys and men.

Adult↗
PubMed1996

Physiological correlates of 3-kilometer running performance in male children.

The purpose of this study was to examine the influence of body fatness, aerobic and anaerobic ability on 3-km running performance in 19 physically active boys (mean +/- SD, age = 10.4 +/- 0.9 yrs). The sum of six skinfolds, VO2 at 8.04 and 9.65 km.hr-1, and VO2max were measured in the laboratory. Run time for 3 km was assessed twice on separate days on a 200-meter indoor track. Prior to each run, every child performed two 55-meter sprints and two vertical jumps. Mean +/- SD values for the sum of skinfolds, %VO2max at each running speed, VO2max and 3-km run time were: 33.9 +/- 14.9 mm; 70.6 +/- 6.6% and 81.0 +/- 7.9%; 54.6 +/- 5.0 ml.kg-1.min-1; 16.41 +/- 2.58 min, respectively. Significant (p < 0.05) correlations were observed between the following variables and run time: sum of skinfolds (r = 0.72); vertical jump (r = 0.67); sprint time (r = 0.59); VO2max (r = 0.61); and, %VO2max at each treadmill speed (r = 0.79 and r = 0.75, respectively). Stepwise multiple regression analysis indicated that the combination of the %VO2max at 8.04 km.hr-1 and vertical jump accounted for 83% (adjusted R2) of the variance in running time (SEE = 1.06 min, p < 0.05). This study suggests that 3-km run time in physically active boys is influenced by aerobic and anaerobic indices as well as body fatness, supporting the notion that children, compared to adults, are not metabolic specialists.

Body Constitution↗
PubMed1995

Ratings of perceived exertion at maximal exercise in children performing different graded exercise test.

The purpose of this study was to examine the rating of perceived exertion (RPE) at maximal exercise in children performing three different graded exercise tests on a treadmill. Eighteen children with a mean +/- SD age of 10.3 +/- 1.4 years volunteered for this study. Each subject performed three different graded exercise test protocols on a treadmill. The protocols consisted of walking only, running only, and combination walk/run. Mean VO2max (ml.kg-1.min-1) during the walking trial (47.3 +/- 5.0) was significantly (p < 0.05) less than during the running (52.1 +/- 4.9) and combination trials (51.9 +/- 5.1). Mean HRmax (bpm) was significantly (p < 0.05) lower during the walking test (195.2 +/- 7.9) compared to the running (202.2 +/- 7.4) and combination tests (202.3 +/- 6.6). Mean RPE at maximal exercise was 18.1 +/- 2.1 in the walking trial, 16.8 +/- 3.0 in the running trial, and 16.8 +/- 2.6 in the combination trial, and was significantly (p < 0.05) greater in the walking trial compared to the other two testing protocols. These data indicate that although VO2max during a walking test is lower, effort sensation is higher compared to protocols that use running as the mode of exercise. The factors involved with RPE selection in this age-group remain to be established.

Child↗
PubMed1994

Cardiovascular adaptations in 8- to 12-year-old boys following a 14-week running program.

This study examined the effects of a 14-week running program on VO2max, as well as cardiac output (Q) and arterial-venous O2 difference (a-vO2 dif) at submaximal intensities corresponding to 50 and 75% of VO2max. Thirteen boys (mean age 10.6 +/- 1.2 yrs) served as experimental subjects while 13 other boys of similar age (mean age 10.2 +/- 1.2 yrs) served as controls. Mean VO2max in the runners increased 13%, from 44.2 +/- 7.0 to 49.9 +/- 6.3 ml.kg-1.min-1. Posttraining VO2 during submaximal and maximal exercise was significantly (p < 0.05) greater in the runners than in the controls. Q and SV exhibited an increase of 10% at each intensity, but posttraining differences between groups were not significant (p > 0.05). A-vO2 dif increased by 8% at 50% of VO2max and by 6% at 75% of VO2max, and was significantly greater in the runners following training. These results indicate that increases in submaximal relative VO2 in children are mediated by increases in a-vO2 dif and Q.

Adaptation, Physiological↗
PubMed1994

The effect of exercise on serum and salivary cortisol in male children.

The purpose of this study was to examine serum and salivary cortisol responses to cycling exercise in male children, 10.6 +/- 0.2 yr (mean +/- SE). Each child performed a graded exercise test on a cycle ergometer to determine VO2max. On a separate day, a 30-min bout of exercise at 70% of VO2max was performed. Blood, obtained from a venous catheter, and saliva samples were collected at rest, at 15 and 30 min of exercise, and 15 min post-exercise. The mean serum cortisol level at 15 min (7.94 +/- 1.43 micrograms.dl-1) and 30 min (8.72 +/- 1.77 micrograms.dl-1) of exercise and at 15 min post-exercise (8.21 +/- 1.59 micrograms.dl-1) were significantly greater than rest (5.54 +/- 0.86 micrograms.dl-1). The increase in salivary cortisol levels over time approached (P = 0.08), but did not reach significance. However, effect size analyses indicated that the increase in salivary cortisol at 30 min of exercise (0.64) and 15 min post-exercise (0.62) was similar to the change in serum cortisol at these same two time points (0.72 and 0.66, respectively). Serum and salivary cortisol were correlated (P < 0.05) at 15 min of exercise (r = 0.77), 30 min of exercise (r = 0.90), and 15 min post-exercise (r = 0.84), but not at rest (r = 0.46). In conclusion, 30 min of submaximal exercise at 70% of VO2max significantly increased serum cortisol level; and salivary and serum cortisol are correlated during and after exercise.

Analysis of Variance↗
PubMed1993

Evaluation of a shallow water running test for the estimation of peak aerobic power.

The purpose of this investigation was to assess the validity of a 500-yard shallow water run test to determine peak aerobic power (VO2peak) and to compare it with the commonly used 1.5-mile run test. Subjects included 15 men and 28 women who completed two trials each of a 500-yard shallow water run test and a 1.5-mile run and then completed a graded exercise test on a treadmill to determine VO2peak. Correlation coefficients with measured VO2peak were -0.89 and -0.80 for the 1.5-mile and 500-yard water runs, respectively. Multiple regression analyses revealed that prediction of VO2peak from 1.5-mile run time was significantly improved by including the 1.5-mile run peak HR (R2 = 0.82, SEE = 3.52 ml.kg-1.min-1). Similarly, for the 500-yard water run test, percent body fat and height were significant additional predictors of VO2peak (R2 = 0.86, SEE = 3.19 ml.kg-1.min-1). We conclude that the 500-yard shallow water run test, especially when used with the descriptive measures of percent body fat and height, can provide a reasonable estimate of an individuals' cardiorespiratory fitness classification. However, caution is advised when administering these tests in older populations or in those with multiple coronary risk factors.

Adolescent↗
PubMed1992

Reliability of the rating of perceived exertion at ventilatory threshold in children.

The purpose of this study was to examine the reliability of the rating of perceived exertion (RPE), using the Borg 6-20 scale, at ventilatory threshold (VT) in children. Thirty children (19 male, 11 female) with a mean +/- SD age of 10.4 +/- 1.1 yrs performed two graded exercise tests for the assessment of VT and VO2max. RPE was recorded throughout each exercise test. There were no significant (p > 0.05) differences between the mean VO2max (50.9 +/- 6.0 vs 51.0 +/- 5.7 ml.kg-1.min-1; r = 0.95) or the mean VO2 at VT (36.2 +/- 4.4 vs 36.7 +/- 4.5 ml.kg-1.min-1; r = 0.87) between trials. The mean RPE at VT during trial 1 (12.4 +/- 2.7) was significantly higher than during trial 2 (11.4 +/- 3.3; p < 0.05). The test-retest reliability correlation for the RPE at VT was r = 0.78. The lower RPE in the second trial may have been due to a greater comfort and familiarity with the testing procedures. The reliability analysis indicates that the RPE at VT within a given child is fairly consistent from trial to trial. However, large inter-individual variability in the RPE at VT (range = 6 to 19) was noted and was not related to variations in the onset of VT. This raises some concern over the use of a given RPE value or range of RPE values in the regulation of exercise intensity for this age group. The test-retest reliability of VT and VO2max in this age group is similar to previous reports.

Child↗
PubMed1992

The effect of psychological strategies upon cardiorespiratory and muscular activity during treadmill running.

Twelve aerobically trained males (age 22 +/- 1.3 yr, range 18-31) were studied to determine the effects of VE and EMG feedback upon cardiorespiratory and muscular activity during one segment of a continuous 36-min bout of treadmill running just below ventilatory threshold (VT). Ventilatory, metabolic, cardiovascular, RPE, and EMG variables recorded during a 12-min feedback segment were compared with those observed during 12-min attentional distraction and control conditions. The three treatments were counterbalanced. Mean VO2 (2987 ml.min-1) remained constant across the three periods as did VCO2 (3102 ml.min-1), HR (168 bpm), RQ (0.95), and O2 pulse (18.5 ml.beat-1). However, VE was significantly reduced during feedback (Fb) as compared with both the distraction (D) and control (C) conditions (mean +/- SE: 83.2 +/- 3.6 vs 86.6 +/- 4.2 and 87.8 +/- 4.2 l.min-1, respectively). This effect was marked by a reduction in respiratory rate (RR) (41.1 +/- 2.1 vs 44.5 +/- 1.9 and 46.8 +/- 1.9 breaths.min-1 for Fb, D, and C, respectively) and an increase in tidal volume (TV) (2115 +/- 144 vs 1904 +/- 110 and 2020 +/- 102 ml.breath-1 for Fb, D, and C, respectively). These changes resulted in significant reductions in VE/VO2 (26.5 +/- 0.7 vs 28.9 +/- 1.0 and 28.3 +/- 0.9 ratio magnitudes), VE/VO2 (28.1 +/- 0.8 vs 30.2 +/- 1.0 and 29.7 +/- 1.0 ratio magnitudes), and PETO2 (105.5 +/- 1.0 vs 108.4 +/- 1.1 and 107.6 +/- 1.2 mm Hg) during Fb as compared with D and C, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1989

The effects of exercise on coronary heart disease risk factors in children.

Coronary heart disease (CHD) is now recognised as a paediatric problem despite the fact that clinical symptoms of this disease do not become apparent until much later in life. Epidemiological studies of risk factors in children have now been conducted. These studies suggest that the risk factors for cardiovascular disease in adults, which include a family history of heart disease, elevated blood lipids (serum cholesterol and triglycerides), obesity, hypertension, smoking, diabetes mellitus and inadequate physical activity, can be identified in children. Several investigators have reported the existence of one or more risk factors in more than 50% of the children they have examined. It is now clear that we can detect most children who are potentially at risk for CHD. The notion of 'tracking' some of the most common CHD risk factors in children has been used in several studies. Results from this type of research indicate that children who are at the extreme end of the distribution and have high levels of blood pressure, adverse lipid levels and are obese will continue to exhibit these coronary risk factors as they grow. The research completed at present does not answer the question of whether children who exhibit a coronary-prone risk factor profile will exhibit this same profile at an age when one is most likely to develop the clinical manifestations of CHD. It does make sense, however, to identify those children who may be at risk for developing premature CHD and to initiate safe interventions such as behaviour modification, changes in diet and increases in physical activity. These have all been shown to alter risk factors which are associated with increased relative risk of CHD in adults. It should be noted that in adults regular aerobic exercise often may alter all risk factors for CHD, including hypertension and diabetes. Whether regular aerobic exercise will induce similar changes in children is not fully understood.

Child↗
PubMed1989

Ventilatory threshold and VO2max changes in children following endurance training.

There are conflicting data with regard to the effect of endurance training in children. On the basis of this information, the effects of 8 wk of run training on ventilatory threshold (VT) and VO2max of eight male children were investigated. Children ranged in age from 10 to 14 yr, with a mean age of 12.4 yr. All subjects were previously untrained. Training consisted of running 4 d.wk-1 for a period of 8 wk. Continuous running was performed 2 d.wk-1 for 10-30 min at 70-80% of VO2max. Interval running was performed the remaining 2 d.wk-1. Repeated intervals of 100-800 m at 90-100% of VO2max were used in this phase of the training. The total distance run for this type of training was 1.5-2.5 km. Incremental treadmill testing prior to and after the training period indicated a 19.4% increase in VT from 30.5 to 36.4 ml.kg-1.min-1 (P less than 0.05). When VT was expressed as a percentage of VO2max, there was a significant (P less than 0.05) increase from 66.6% to 73.8%. VO2max increased 7.5% from 45.9 to 49.4 ml.kg-2.min-2 (P less than 0.05). None of these changes was noted in eight age- and size-matched children who served as control subjects. The results of this study indicate that 8 wk of endurance running training which is of sufficient frequency, intensity, and duration can significantly improve VT and aerobic capacity in male children.

Adolescent↗