PubMed Health⌕ Search

Biomedical subjects

W D McArdle

Publications and source records attributed to W D McArdle.

At least 19 recordsLinked to original sources
PubMed1997

Thermal and metabolic responses to cold-water immersion at knee, hip, and shoulder levels.

To examine the effect of cold-water immersion at different depths on thermal and metabolic responses, eight men (25 yr old, 16% body fat) attempted 12 tests: immersed to the knee (K), hip (H), and shoulder (Sh) in 15 and 25 degrees C water during both rest (R) or leg cycling [35% peak oxygen uptake; (E)] for up to 135 min. At 15 degrees C, rectal (Tre) and esophageal temperatures (Tes) between R and E were not different in Sh and H groups (P > 0.05), whereas both in K group were higher during E than R (P < 0.05). At 25 degrees C, Tre was higher (P < 0.05) during E than R at all depths, whereas Tes during E was higher than during R in H and K groups. Tre remained at control levels in K-E at 15 degrees C, K-E at 25 degrees C, and in H-E groups at 25 degrees C, whereas Tes remained unchanged in K-E at 15 degrees C, in K-R at 15 degrees C, and in all 25 degrees C conditions (P > 0.05). During R and E, the magnitude of Tre change was greater (P < 0.05) than the magnitude of Tes change in Sh and H groups, whereas it was not different in the K group (P > 0.05). Total heat flow was progressive with water depth. During R at 15 and 25 degrees C, heat production was not increased in K and H groups from control level (P > 0.05) but it did increase in Sh group (P < 0.05). The increase in heat production during E compared with R was smaller (P < 0.05) in Sh (121 +/- 7 W/m2 at 15 degrees C and 97 +/- 6 W/m2 at 25 degrees C) than in H (156 +/- 6 and 126 +/- 5 W/m2, respectively) and K groups (155 +/- 4 and 165 +/- 6 W/m2, respectively). These data suggest that Tre and Tes respond differently during partial cold-water immersion. In addition, water levels above knee in 15 degrees C and above hip in 25 degrees C cause depression of internal temperatures mainly due to insufficient heat production offsetting heat loss even during light exercise.

Adult↗
PubMed1992

Thermal responses of men and women during cold-water immersion: influence of exercise intensity.

The influence of exercise intensity on thermoregulation was studied in 8 men and 8 women volunteers during three levels of arm-leg exercise (level I: 700 ml oxygen (O2).min-1; level II: 1250 ml O2.min-1; level III: 1700 ml O2.min-1) for 1 h in water at 20 and 28 degrees C (Tw). For the men in Tw 28 degrees C the rectal temperature (Tre) fell 0.79 degree C (P less than 0.05) during immersion in both rest and level-I exercise. With level-II exercise a drop in Tre of 0.54 degree C (P less than 0.05) was noted, while at level-III exercise Tre did not change from the pre-immersion value. At Tw of 20 degrees C, Tre fell throughout immersion with no significant difference in final Tre observed between rest and any exercise level. For the women at rest at Tw 28 degrees C, Tre fell 0.80 degree C (P less than 0.05) below the pre-immersion value. With the two more intense levels of exercise Tre did not decrease during immersion. In Tw 20 degrees C, the women maintained higher Tre (P less than 0.05) during level-II and level-III exercise compared to rest and exercise at level I. The Tre responses were related to changes in tissue insulation (I(t)) between rest and exercise with the largest reductions in I(t) noted between rest and level-I exercise across Tw and gender. For mean and women of similar percentage body fat, decreases in Tre were greater for the women at rest and level-I exercise in Tw 20 degrees C (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Lipid and lipoprotein profiles relate to peak aerobic power in spinal cord injured men.

The relationship between peak VO2 and serum lipids, lipoproteins, and apolipoproteins was assessed in nine traumatic spinal cord injured (SCI), active, male volunteers. Mean (SD) age, height, and weight were 30.6 (11.6) yr, 171.1 (11.3) cm, and 74.2 (12.5) kg, respectively. Peak VO2 (X = 2.13 l.min-1) was assessed by a graded arm-crank test to maximum, percent body fat (X = 28.7%) by densitometry, and lipid profile by measures of serum triglycerides, total cholesterol (TC), high and low density lipoprotein cholesterol (HDL-C and LDL-C, respectively), apolipoproteins (apoA-1, apoB), and various ratios of lipids, lipoproteins, and apolipoproteins. Significant inverse relationships emerged between peak VO2 and TC/HDL-C (r = -0.86; P less than 0.01), apoB/apoA-1 (r = -0.75; P less than 0.05), triglycerides (r = -0.73; P less than 0.05), and LDL-C/HDL-C (r = -0.72; P less than 0.05). Direct correlations (P less than 0.05) were demonstrated between peak VO2 and apoA-1/apoB (r = 0.71) and HDL-C/apoA-1 (r = 0.64). The present results indicate that, for active, mid-to-lower thoracic SCI men, the putative atherogenic and antiatherogenic lipid, lipoprotein, and apolipoprotein indices are significantly related to peak VO2 in a manner similar to that described for the able-bodied. These findings indicate the relevance of aerobic fitness assessment in planning CHD prevention strategies for the SCI.

Adult↗
PubMed1990

Cardiovascular adjustments to exercise distributed between the upper and lower body.

The present study examined the hemodynamic differences between upper- and lower-body exercise where the total power output (PO) was proportionally distributed between the upper and lower body. Six males completed five combinations of arm-leg exercise at maximal and three submaximal intensities. The ratio of arm PO to total PO for each exercise combination was 0, 25, 50, 75, and 100%. At each submaximal intensity, VO2 and cardiac output (Q) were not different (P greater than 0.05) across exercise combinations. Likewise, heart rate (HR) responses were not different for 0, 25, 50, and 75% at level 1 (mean = 102, 102, 106, 106 beats.min-1, respectively), level 2 (mean = 114, 110, 119, 118 beats.min-1, respectively), and level 3 (mean = 127, 124, 132, 131 beats.min-1, respectively). However, HR for 100% (arm-only exercise) tended to be higher than 0% at level 1 (delta HR = 10 beats.min-1; P less than 0.10), level 2 (delta HR = 12 beats.min-1, P less than 0.06) and level 3 (delta HR = 10 beats.min-1; P less than 0.06). At level 1, stroke volume (SV) remained essentially unchanged from 0-75%, while SV at 100% (108 ml) was slightly though not significantly lower (P less than 0.10) than 0% (125 ml). At exercise levels 2 and 3, SV remained unchanged for 0 and 25%; however, SV at 50, 75, and 100% were generally lower (P less than 0.05) compared with 0%. These results indicate that involving the leg musculature to varying degrees during arm-leg exercise attenuates the hemodynamic differences observed during strict upper body versus strict lower body exercise.

Adult↗
PubMed1984

Thermal adjustment to cold-water exposure in resting men and women.

Thermoregulatory responses were studied in 10 men and 8 women at rest in air and during 1-h immersion in water at 20, 24, and 28 degrees C. For men of high body fat (27.6%), rectal temperature (Tre) and oxygen consumption (VO2) were maintained at air values at all water temperatures (Tw). For men of average (16.8%) and low (9.2%) fat the change in Tre (delta Tre) was inversely related to body fat at all Tw with VO2 increasing to 1.07 l X min-1 for a -1.6 degrees C delta Tre for lean men. For women of average (25.2%) and low (18.5%) fat Tre decreased steadily during immersion at all Tw. The greatest changes occurred at 20 degrees C with little differences in delta Tre and VO2 noted between these groups of women. In comparison with males of similar percent fat, Tre dropped to a greater extent (P less than 0.05) in females at 20 and 24 degrees C. Stated somewhat differently, lean women with twice the percentage of fat have similar delta Tre as lean men at all Tw. For delta Tre greater than -1.0 degree C men showed significantly greater (P less than 0.05) thermogenesis compared with women. The differences in thermoregulation between men and women during cold stress at rest may be due partly to the sensitivity of the thermogenic response as well as the significant differences in lean body weight and surface area-to-mass ratio between the sexes.

Adipose Tissue↗
PubMed1984

Thermal adjustment to cold-water exposure in exercising men and women.

Thermoregulatory responses were studied in 10 men and 8 women during 36-W exercise for 1 h in air and water at 20, 24, and 28 degrees C. Men were classified as high (27.6%; n = 2), average (16.8%; n = 4), and low (9.2%; n = 4) percent body fat, whereas women were classified as average (25.2%; n = 4) and low (18.5%; n = 4) fat. For both men and women, exercise of about 1.7 l O2 X min-1 was beneficial in either preventing or retarding the fall in rectal temperature (Tre) observed in a previous study for the same subjects at rest. The greatest thermal strain was noted for the leanest subjects. However, in no instance did exercise facilitate a drop in Tre compared with resting conditions. Despite a larger surface area-to-mass ratio (P less than 0.05) and less effective thermoregulation for women at rest compared with men, essentially similar thermoregulatory responses were observed for both sexes during exercise at each water temperature. For both the men and women, the thermoregulatory benefits of exercise were due largely to the added heat production from physical activity. For the female, an additional benefit of exercise may in part be derived from a more favorable distribution of subcutaneous fat over the active musculature.

Adipose Tissue↗
PubMed1984

Specificity of arm training on aerobic power during swimming and running.

The specificity of aerobic training for upper-body exercise requiring differing amounts of muscle mass was evaluated in 25 college-aged male recreational swimmers who were randomly assigned to either a non-training control group (N = 9), a 10-wk swim(S)-training group (N = 9), or a group that trained with a standard swim-bench pulley system (SB; N = 7). For all subjects prior to training, tethered-swimming peak VO2 averaged 19% below treadmill values (P less than 0.01), while SB-ergometry peak VO2 was 50% and 39% below running and swimming values, respectively (P less than 0.01). Significant (P less than 0.01) increases of peak VO2 in tethered swimming (11%) and SB (21%) were observed for the SB-trained group, while the S-trained group improved (P less than 0.01) 18% and 19% on the tethered swimming and SB tests, respectively. No changes were observed during treadmill running, and the control subjects remained unchanged on all measures. Comparisons between training groups indicated that although both groups improved to a similar extent when measured on the swim bench, the 0.53 l X min-1 improvement in tethered-swimming peak VO2 for the S-trained group was greater (P less than 0.05) than the 0.32 l X min-1 increase noted for the SB-trained group. The comparisons between SB and S exercise vs treadmill exercise support the specificity of aerobic improvement with training and suggest that local adaptations contribute significantly to improvements in peak VO2. Furthermore, the present data indicate that SB exercise activates a considerable portion of the musculature involved in swimming, and that aerobic improvements with SB training are directly transferred to swimming.

Adult↗
PubMed1984

Temporomandibular joint repositioning and exercise performance: a double-blind study.

In the present study, the effects of temporomandibular joint (TMJ) repositioning by use of an acrylic appliance on maximum and submaximum physiologic and performance measures were evaluated in seven male and four female volunteers with documented TMJ malalignment. In an attempt to remove design inadequacies of previous research in this area, a double-blind strategy was utilized. Subjects were randomly assigned to each of four conditions: 1) normal, without a bite splint, 2) with a placebo splint with no occlusal contact so as to maintain normal jaw position, 3) with a splint that optimized jaw position, and 4) with a splint that magnified the subjects normal degree of malocclusion. Measurements were taken of visual reaction time and movement time, muscular strength of the grip, elbow flexors, and leg extensors, submaximal and maximal oxygen uptake, perceived exertion, anaerobic power output, and all-out working capacity in both arm and leg exercise on a cycle ergometer. Analysis of variance for repeated measures indicated that in no instance were the differences in mean scores on physiologic and performance measures with TMJ repositioning or placebo statistically significant when compared with the normal condition. This was the case for the group as a whole or when the five subjects with the greatest TMJ dysfunction were analyzed separately. These findings strongly support the contention that the beneficial effects of short-term TMJ repositioning on exercise performance noted in previous reports may be the result of inadequacies in research design and evaluation rather than the true effects of the bite splint.

Adolescent↗
PubMed1982

Cardiorespiratory responses to ballet exercise and the VO2max of elite ballet dancers.

Physiologic responses to ballet exercise and VO2max during treadmill running were studied in elite professional ballet dancers (7 men, 8 women; age 20-30 yr) from American Ballet Theatre. Ten dancer were studied during standard 1-h ballet classes consisting of 28 min of barre and 32 min of center floor exercise. Eight dancers performed maximal treadmill running tests yielding VO2max values (ml . min-1 . kg-1) of 48.2 (range 43.8-51.9) for men and 43.7 (range 40.9-50.1) for women. Mean VO2 (ml . min-1 . kg-1) during barre exercise was 18.5 (38% VO2max) for men and 16.5 (38% VO2max) for women; during center floor exercise 26.3 (55% VO2max) for men and 20.1 (46% VO2max) for women, with a peak of 77% VO2max for a male dancer. Mean caloric output values (kcal . kg-1 . min-1) during barre exercise were 0.09 and 0.08 for men and women, respectively, and during center floor exercise 0.13 for men and 0.10 for women, with a peak of 0.18 for one male dancer. Estimated net caloric outputs for the entire ballet class averaged 200 kcal . h-1 for women and 300 kcal . h-1 for men. During barre exercise, HR was below the training sensitive zone (70% HR max) for significant periods of time. Peak HR (beats . min-1) was relatively high during allegro center floor exercise, averaging 178 (92% HR max) and 158 (85% HR max) for men and women, respectively. However, these were maintained for only brief durations similar to sprint or burst activities. We conclude that these physiologic data obtained during ballet class represent only a relatively modest stimulus for augmenting aerobic (VO2max). In conjunction with the strong isometric component in ballet exercise, along with the sprint or burst component of ballet exercise, these factors would produce in elite ballet dancers VO2max values in the range of non-endurance athletes.

Adult↗
PubMed1978

Metabolic and cardiovascular adjustment to arm training.

Maximal and submaximal metabolic and cardiovascular measures and work capacity were studied in control (n = 7) and experimental (n = 9) subjects (S's) during arm work prior to and following 10 wk of interval arm training. These measures were oxygen uptake (VO2), minute ventilation (VE), heart rate (HR), respiratory exchange ratio (R), cardiac output (Q), stroke volume (SV), and arteriovenous oxygen difference ((a--v)O2 diff). In addition, maximal oxygen uptake (VO2max) was measured in both groups during treadmill running. Experimental S's showed significant increases (P less than 0.01) in peak VO2 (438 ml.min-1), max VE (17.7 l.min-1), max (a--v)O2 diff (20.8 ml.l-1), and work time (9.2 min) during arm ergometry, while maximum values of Q, SV, HR, and R remained unchanged. In addition, submaximal heart rates were significantly lower during arm ergometry after training. VO2max during treadmill running remained essentially unchanged. No changes in metabolic and physiological measures were noted for the controls after the 10-wk training period. The results support the concept of training specificity for VO2max, and indicate that the improvement in peak VO2 in arm ergometry reflects enhanced oxygen utilization due to an expanded (a--v)O2 diff.

Adult↗
PubMed1978

Specificity of run training on VO2 max and heart rate cganges during running and swimming.

To further evaluate the specificity of aerobic training, maximum physiologic measures (VO2, VE, HR, and R) and submaximal exercise heart rate were determined in control (N = 8) and experimental (N = 11) subjects prior to and following 10-week interval run training. Experimental subjects significantly increased (P less than 0.01) treadmill VO2 max by 252 ml O2 or 6.3%. This was siginificantly larger (P less than 0.01) than the 87 ml O2 or 2.6% increase (P less than 0.05) observed during swimming. Max HR decreased significantly in both forms of exercise. In addition, heart rate at two submaximal work levels during running and swimming was significantly lower after training. No changes in metabolic and physiologic measures were demonstrated for the controls after the 10-wk period. These results further support the concept of the specificity of the metabolic adaptation to aerobic training and strongly suggest that local adaptations in skeletal muscle significantly contribute to improvement in VO2 max. However, running may produce a general training adaptation in maximal and submaximal heart rate.

Adolescent↗
PubMed1976

Metabolic and cardiovascular adjustment to work in air and water at 18, 25, and 33 degrees C.

By use of successive increments of discontinuous work with an arm-leg cycle ergometer the VO2, Q, SV, and HR were studied in six male subjects at rest and during exercise in air and in water at 18, 25, and 33 degrees C. The Q values obtained by CO2 rebreathing were reproducible. VO2 was linearly related to work with the plots for air and 33 degrees C water being similar. However, during work in 25 and 18 degrees C water, the VO2 averaged 9.0% (150 ml) and 25.3% (400 ml) higher, respectively, than values observed in 33 degrees C water, with the largest differences observed in leaner subjects. The plot of HR-VO2 was linear and almost identical during work in air and 33 degrees C water, but shifted significantly to the right in cooler water. VO2 averaged 250-700 ml higher in cold water compared to air and 33 degrees C water at a given mean heart rate. The Q vs. VO2 line was similar during work in air and in water with no effect of water or temperature. At similar levels of VO2, SV was significantly larger (P less than 0.05) in 25 and 18 degrees C water than in air or 33 degrees C water. Consequently, the reduction in heart rate during work in cold water was entirely compensated for by a proportionate increase in the SV of the heart. Q was therefore maintained at similar levels of energy expenditure in air and in 18, 25, and 30 degrees C water.

Acclimatization↗
PubMed1975

Specificity of swim training on maximum oxygen uptake.

The present study was designed to evaluate the specificity-generality of the cardiorespiratory adaptation to swim training. Fifteen male, college age, recreational swimmers utilized interval swim training procedures 1 h/day, 3 days/wk for 10 wk. Maximum physiological measures (Vo2, Ve, HR, R, and work time) were determined prior to and following swim training during treadmill running and tethered swimming Vo2max tests. Identical measures were made on 15 control subjects who did not participate in any form of training. As a result of training, the experimental subjects significantly increased (all P is less than 0.01) their swimming Vo2max (380 ml/min) max Ve (14.9 l/min,btps) and max swim time (4.0 min), and significantly decreased (P is less than 0.05) their max HR (3.5 beats/min). However, there was no significant improvement in Vo2max when the same subjects were evaluated by the treadmill running test. Differences in Vo2max and associated measures during running and swimming tests remained essentially unchanged for control subjects. The results of the present study clearly demonstrate the specificity of the cardiorespiratory adaptation to swim training in male recreational swimmers.

Adaptation, Physiological↗