Maximal Treadmill Running Research Articles

INFLUENCE OF EXERCISE TRAINING ON COLLAGEN TRAITS OF MYOCARDIUM AND SKELETAL MUSCLE FROM INFARCTED RATS 637

The influence of exercise training on collagen accretion and mature crosslinking were assessed in viable left ventricle free wall (LVFW) and skeletal muscle of infarcted rats. Infarcts (11% of heart weight) were surgically induced in two groups of 4 mo-old rats (sedentary and exercise trained). The exercise trained group performed 10 wk of treadmill running (6× 60 min per wk). Treadmill speed was increased from 10 m·min-1 to 22 m·min-1 over the 10 wk program. Rats were sacrificed at 8 mo of age, heart and soleus muscle were excised, and entire left ventricle dissected from the rest of the myocardium and separated into the LVFW and scar. LVFW and soleus muscle were analyzed for concentrations of collagen ([coll]) and the nonreducible collagen crosslink hydroxylysylpyridinoline ([HP]). Maximal treadmill running speeds were significantly greater (p≤0.05) in the trained rats (40.5±14.2 m·min-1) as compared to the sedentary group (25.4±3.7 m·min-1). [Coll] was unaltered by training in either the LVFW or soleus muscle. [HP] decreased significantly (p≤0.05) in both the LVFW(0.29±0.03 vs 0.41±0.02 mol HP·mol collagen-1) and soleus (0.32±0.03 vs 0.52±0.07 mol HP·mol collagen-1) with training. These results mirror those seen for normal animals exposed to exercise training. Furthermore, exercise training seems to normalize crosslinking values in infarcted LVFW to those seen in in young healthy hearts. Attenuated collagen crosslinking associated with exercise training in infarcted myocardium and corresponding soleus muscle may have resulted from accretion of less mature collagen due to increased turnover. Diminished crosslinking in both heart and soleus muscle imply reduced stiffness and may account for improved heart function and exercise capacity noted in trained humans and animals post-infarction.

Three day eventing: thermoregulatory considerations

require estimation of maximal values from submaximal measurements, introducing an added error into calculations. Variables such as Vlso and Vlg0 are considered inadequate due to the variability in heart rates at low exercise intensities. Some workers are now relating submaximal to maximal values, such as V2#HRmaX, HRI&Rma, and Lal&amax. This increases the accuracy over the submaximal value alone, but it does necessitate the use of a maximal exercise test. To date, most tests have examined aerobic capacity because anaerobic capacity is more difficult to measure. The measurements of maximum accumulated oxygen deficit (MAOD), presented by Eaton et al. (1995) may provide an indication of anaerobic capacity. However, this measurement requires a rapid acceleration, maximal speed treadmill run.

Exercise intensity dependent inhibition of 1-methyl-1-nitrosourea induced mammary carcinogenesis in female F-344 rats.

The objective of this experiment was to evaluate the effects of treadmill exercise on tumor induction in an experimental model for breast cancer. Female F-344 rats were injected i.p. with 50 mg MNU/kg body wt at 50 and 57 days of age. Animals were assigned to one of five groups: sham exercise or 35% or 70% maximal treadmill running intensity for 20 or 40 min/day, 5 days per week. These work rates represent an exercise intensity level generally considered insufficient to improve cardiovascular fitness (35% maximal intensity) or an aerobic level of exercise sufficient to improve cardiovascular fitness in humans (70% maximal intensity). Rats were exercised for 3 months following carcinogen administration at which time the experiment was terminated. Mammary cancer incidence was reduced by as much as 37% and cancer multiplicity by < 60% at the highest exercise intensity. Unexpectedly, the degree of protection against cancer was proportional to the intensity but not to the duration of exercise.

Is leg muscle mass decisive in reaching a plateau in oxygen uptake during maximal treadmill running? Analysis of data from the Amsterdam growth and health study.

Within the framework of a longitudinal study, the Amsterdam Growth and Health Study followed a group of males and females from their teens into early adulthood. Directly measured maximal oxygen uptake (VO2 max) was determined five times in 97 males and 103 females between 13 and 21 years of age during a constant speed (8 km/hr) and variable slope treadmill run to exhaustion. A change in oxygen uptake (VO2 ) of < 150 ml between the second last and final minute of the test was used as the criterion to determine the attainment of a plateau or leveling-off (LO) in VO2 . The purpose of this study was to investigate the relationship between VO2 max and the leveling-off criterion and other factors associated with the plateau phenomenon in this sample with increasing age. The VO2 max measurements over the years showed that 44-57% of males and 24-42% of females did not show a plateau. Moreover, subjects who did not reach leveling-off (no-LOs) showed slightly higher VO2 max values than subjects who reached the leveling-off criterion (LOs). These differences are significant (P < 0.05) in males from age 14.5 on, and in females only at age 21.5. Males who did not demonstrate a plateau in VO2 had a significantly higher total fat-free mass and lean leg volume (LLV) than males who demonstrated a plateau, but were not different in stature and weight. However, in females these differences were not significant. The apparent sex difference can be explained by the much smaller increase (25%) in LLV in females than in males. These results can be explained by the limitations of VO2 max by central and/or peripheral circulating factors. One possibility could be that during maximal uphill running, relatively less vasoconstriction occurs in the arterioles of larger exercising leg muscles, which permits an upward shift in VO2 and an increased demand on central oxygen transport mediated by increased peripheral metabolism. © 1994 Wiley-Liss, Inc.

Seasonal variation of selected performance parameters in épée fencers.

In this study, anthropometric measurements were carried out on seven British international male épée fencers, using a maximal treadmill running test, a 20-s Wingate-type test, and isokinetic dynamometry. Testing was conducted on two occasions, 5 to 6 months apart, during mid-off-season (preparation) and mid-in-season (competition) periods. Maximal oxygen intake (VO2max) and maximal respiratory exchange ratio (Rmax) were among the parameters obtained from the treadmill test, while peak and mean anaerobic power outputs were measured during a 20-s maximal effort. Knee extensor and flexor muscle forces from both dominant (leading) and non-dominant (trailing) legs were assessed at 1.04, 3.14 and 4.19 rad sec-1. Statistical analyses revealed lower mean VO2max (P < 0.05) and mean Rmax values (P < 0.02) at the in-season assessments compared with off-season. In-season testing also demonstrated significantly lower peak torques for both dominant and non-dominant knee extensors compared with off-season assessments at all velocities (P < 0.05 to P < 0.004). Furthermore, in-season peak torque for the non-dominant leg flexors was lower (P < 0.03) at 4.19 rad sec-1 than off-season. We conclude that current training practices may account for the observed seasonal variations in performance related physiological parameters in fencers.

Recovery of pulmonary diffusing capacity after maximal exercise.

Pulmonary diffusing capacity (DICO), together with spirometric variables, arterial oxygen tension (paO2) and cardiac output were determined before and at intervals after maximal arm cranking, treadmill running and ergometer rowing. Independent of the type of exercise, D1CO increased immediately post-exercise from a median 13.6 (range 7.3-16.3) to 15.1 (9.3-19.6) mmol min-1 kPa-1 (P < 0.01). However, it decreased to 11.6 (6.9-15.5) mmol min-1 kPa-1 (P < 0.01) after 24 h with cardiac output and paO2 at resting values, and D1CO normalized after 20 h. Thoracic electrical impedance at 2.5 and 100 kHz increased slightly post-exercise, indicating a decrease in thoracic fluid balance, and there were no echocardiographic signs of left ventricular failure at the time of the decrease in D1CO. Also, active muscle (limb) circumference and volume, and an increase in haematocrit from 43.8 (38.0-47.0) to 47.1 (42.7-49.8) (P < 0.01), had normalized at the time of the decrease in D1CO. Vital capacity, forced vital capacity, forced expiratory volume in 1 s, peak and peak mid-expiratory flows did not change. However, total lung capacity increased from 6.8 (5.0-7.6) to 7.0 (5.1-7.8) litres (P < 0.05) immediately after exercise and remained elevated at 6.9 (5.1-8.7) litres (P < 0.05) when a decrease in D1CO was noted. The results demonstrate that independent of the type of maximal exercise, an approximate 15% reduction in D1CO takes place 2-3 h post-exercise, which normalizes during the following day of recovery.

Heart size and maximal cardiac output are limited by the pericardium.

We tested the hypothesis that the pericardium, by restricting heart size, limits maximal cardiac output and oxygen consumption. We studied 15 pigs. Five underwent maximal treadmill running before and 14-21 days after thoracotomy and pericardiectomy; these pigs also received sequential volume infusions to determine end-diastolic pressure-dimension relationships. Five underwent maximal treadmill running before and 14-21 days after thoracotomy (pericardium undisturbed) to determine the effect of thoracotomy on exercise performance. Finally, five underwent thoracotomy, instrumentation, loose closure of the pericardium, and sequential volume infusions to determine the effect of thoracotomy without pericardiectomy on end-diastolic pressure-dimension relationships. Pericardiectomy caused similar increases in maximal cardiac output (29% increase; P = 0.007) and maximal oxygen consumption (31% increase; P = 0.02). These results were associated with increased left ventricular end-diastolic dimension (10% increase; P = 0.01) and an estimated 33% increase in end-diastolic volume. In addition, left ventricular mass was increased by pericardiectomy (18% increase; P < 0.04). Thus the pericardium, by limiting utilization of the Starling mechanism, limits maximal cardiac output, and the limit to cardiorespiratory performance lies not in oxygen utilization, but in oxygen delivery. Furthermore, removal of pericardium is associated with myocardial hypertrophy.

Seasonal deterioration of selected physiological variables in elite male skiers.

The purpose of this study was to determine whether seasonal deterioration in physiological variables could be observed in skiers. Eighteen international male British downhill, free-style, and speed skiers were subjected to a maximal treadmill running test, a 30-s Wingate test, and isokinetic dynamometry at the beginning, middle, and end of the 1989-90 competition season. Maximal oxygen intake (VO2max) and respiratory anaerobic threshold (T vent) were among the parameters measured on the treadmill test, while peak and mean power outputs were measured during the Wingate test. During dynamometry, knee flexors and extensors were bilaterally assessed at 1.04 and 3.14 rad.s-1. Mean VO2max (p < 0.01) and mean T vent (p < 0.05) were lower at the end compared to the beginning, but not compared to the middle of the competition season. The isokinetic test demonstrated lower mean peak torques at 1.04 rad.s-1, for the knee extensors measured at the end of the season, compared with both the start (p < 0.01) and the middle (p < 0.05). Also at 1.04 rad.s-1, knee flexors produced lower torques at the end than the start of the season (p < 0.05). No further statistical differences were found. It was concluded that seasonal deterioration in key physiological variables such as aerobic endurance and muscle strength, can be observed in elite alpine skiers, and that in-season fitness training programmes should take account of this.

Oxygen uptake during running as related to body mass in circumpubertal boys: a longitudinal study.

To investigate the effect of endurance training on physiological characteristics during circumpubertal growth, eight young runners (mean starting age 12 years) were studied every 6 months for 8 years. Four other boys served as untrained controls. Oxygen uptake (VO2) and blood lactate concentrations were measured during submaximal and maximal treadmill running. The data were aligned with each individual's age of peak height velocity. The maximal oxygen uptake (VO2max; ml.kg-1.min-1) decreased with growth in the untrained group but remained almost constant in the training group. The oxygen cost of running at 15 km.h-1 (VO2 15, ml.kg-1.min-1) was persistently lower in the trained group but decreased similarly with age in both groups. The development of VO2max and VO2 15 (l.min-1) was related to each individual's increase in body mass so that power functions were obtained. The mean body mass scaling factor was 0.78 (SEM 0.07) and 1.01 (SEM 0.04) for VO2max and 0.75 (SEM 0.09) and 0.75 (SEM 0.02) for VO2 15 in the untrained and trained groups, respectively. Therefore, expressed as ml.kg-0.75.min-1, VO2 15 was unchanged in both groups and VO2max increased only in the trained group. The running velocity corresponding to 4 mmol.l-1 of blood lactate (nu la4) increased only in the trained group. Blood lactate concentration at exhaustion remained constant in both groups over the years studied. In conclusion, recent and the present findings would suggest that changes in the oxygen cost of running and VO2max (ml.kg-1.min-1) during growth may mainly be due to an overestimation of the body mass dependency of VO2 during running.(ABSTRACT TRUNCATED AT 250 WORDS)

Muscle mass effect on arterial desaturation after maximal exercise

We measured arterial oxygen saturation before and immediately after randomly allocated 6 min of "all-out" maximal arm cranking, treadmill running, and ergometer rowing in 10 men and women with a median maximal oxygen uptake of 4.47 (range 3.22-5.34) 1.min-1. Arterial saturation for oxygen was unaltered after arm cranking, but decreased 1.7 (-2.5-6.0) % (P less than 0.05) after running, and 2.2 (1.0-8.7) % (P less than 0.01) after rowing. Arterial saturation was inversely related to capillary blood lactate, which reached 11.8 (7.4-14.0), 12.6 (8.9-18 2), and 14.3 (12.0-19.3) mmol.l-1 (P less than 0.01), respectively, and arterial bicarbonate fell to 15.0 (13.0-23.6), 12.4 (7.2-20.4), and 10.8 (0.0-12.5) mmol.l-1 (P less than 0.01). Thus, pH decreased to 7.25 (7.22-7.40), 7.17 (6.95-7.35), and 7.09 (6.84-7.19) (P less than 0.01). When measured immediately post-exercise, arterial oxygen tension was unchanged or elevated from rest, eliminating the possibility that the arterial desaturation was caused by a pulmonary diffusion limitation. The results of this investigation show that arterial desaturation associated with maximal exercise takes place in proportion to the involved muscle mass, as do deviations in blood lactate, bicarbonate, and hydrogen concentrations.

Differences in Peak Physiological Responses During Running, Cycling and Swimming

Peak physiological responses were compared in 12 male triathletes during maximal treadmill running (TR), cycle ergometry (CE) and tethered swimming (TS) tests. Expired air was measured continuously during TR, CE and during the last minute of each workload during TS. Heart rate (HR) was measured from electrocardiogram tracings during TR and CE, and from telemetry during TS. Blood lactate concentration (HLa) was measured four minutes after each maximal test with a YSI Model 23L analyzer. Significant differences (p < 0.05) were observed in all peak physiological responses except HLa. Mean HLa was 6.9, 7.8 and 8.0 mmol•l–1 after maximal running, cycling and swimming, respectively. Peak O2 relative to body weight was significantly different among TR, CE and TS (67.0, 62.9 and 59.4 ml•kg–1•min–1, respectively). Mean O2 peak during CE and TS was 94 percent and 89 percent, respectively, of the TR value. Peak HR during TS was significantly lower by approximately 15 and 22 bpm compared to CE and TR, respectively. Peak ventilation and respiratory exchange ratio were also significantly lower during TS compared to CE and TR. These data suggest that athletes who are well trained in several modes of exercise (swimming, cycling and running) exhibit mode-specific differences in peak physiological responses other than HLa. These differences should be considered when determining optimal training intensities based on either peak O2 or HR.

Physiologic responses to maximal treadmill and deep water running in men and women

Maximal physiologic responses to treadmill running and deep water running using a flotation device were compared in 12 trained men and 12 trained women. Although the men had significantly higher ventilation volumes, VO2max (liters of oxygen per minute and milliliters of oxygen per kilogram per minute), there were no significant differences in maximal heart rates or respiratory exchange ratios between the sexes. Significantly lower ventilation volumes, VO2max (LO2.min-1 and mlO2.kg-1.min-1), and heart rates were obtained in response to maximal water running compared to treadmill running, regardless of gender. Neither the men's nor women's maximal respiratory exchange ratios were significantly different between modes. The analysis of variance indicated that there were no significant interactions for any of the maximal responses to the tests between the sexes. The magnitude of these differences is similar to that found between treadmill running and cycling ergometry and should not preclude deep water running as a training technique. Caution, however, is advised if the training intensity is to be prescribed on the basis of land-determined heart rates.

Effect of inosine supplementation on 3-mile treadmill run performance and &amp;OV0312;o2 peak

The purpose of this study was to investigate the ergogenic effect of oral inosine (IN) supplementation (6,000 mg.d-1 for 2 d) upon 3-mile run time (3MTIME) and VO2 peak. Nine highly trained endurance runners participated in a double-blind, placebo (PL), crossover study. Each subject undertook an IN or PL trial, consisting of three exercise tests: a submaximal warm-up run (SUBRUN), a competitive 3-mile treadmill run (3MRUN), and a maximal treadmill run (MAXRUN) to determine VO2 peak and time to exhaustion (MAXTIME). Additional measurements during the 3MRUN and MAXRUN included oxygen uptake (VO2), ventilation (VE), respiratory exchange ratio (R), and ratings of perceived exertion (RPE); blood samples were also taken prior (PRERUN) to the SUBRUN test and following the SUBRUN, 3MRUN, and MAXRUN tests in order to assess glucose, pyruvate, lactate, phosphorus, 2,3-DPG, hemoglobin, and uric acid. Analyses of the data revealed no significant effect of oral IN supplementation either upon 3MTIME (IN = 18.31 +/- 1.21; PL = 18.33 +/- 1.15 min) or VO2 peak (IN = 58.6 +/- 5.1; PL = 60.7 +/- 4.5 ml O2.kg-1.min-1) or upon other dependent variables. MAXTIME was significantly longer during the PL trial (P less than 0.05), suggestive of a possible impairment effect of oral IN supplementation. Based upon our data, we conclude that IN is not an effective ergogenic aid to enhance athletic performance of an aerobic nature.

Cardiovascular changes associated with decreased aerobic capacity and aging in long-distance runners

Fifty-five male runners aged between 30 to 80 years were examined to determine the relative roles of various cardiovascular parameters which may account for the decrease in maximal oxygen uptake (VO2max) with aging. All subjects had similar body fat composition and trained for a similar mileage each week. The parameters tested were VO2max, maximal heart rate (HRmax), cardiac output (Q), and arteriovenous difference in oxygen concentration (Ca-Cv)O2 during graded, maximal treadmill running. Average body fat and training mileage were roughly 12% and 50 km.week-1, respectively. The average 10-km run-time slowed significantly by 6.0%.decade-1 [( 10-km run-time (min) = 0.323 x age (years) + 24.4] (n = 49, r = 0.692, p less than 0.001]. A strong correlation was found between age and VO2max [( VO2max (ml.kg-1.min-1) = -0.439 x age + 76.5] (n = 55, r = -0.768, p less than 0.001]. Thus, VO2max decreased by 6.9%.decade-1 along with reductions of HRmax (3.2%.decade-1, p less than 0.001) and Q (5.8%.decade-1, p less than 0.001), while no significant change with age was observed in estimated (Ca-Cv)O2. It was concluded that the decline of VO2max with aging in runners was mainly explained by the central factors (represented by the decline of HR and Q in this study), rather than by the peripheral factor (represented by (Ca-Cv)O2).

Behavioral Effects of Multiple Scba Stressors: Safety Research for Recommending Federal Standards

This paper reports the effects of self-contained breathing apparatus (SCBA) stressors and work intensity on mental functioning and reported clinical symptoms. A methodology involving maximal exertion treadmill running (simulation of an emergency-like escape from an underground mine following a disaster) was used in addressing specific issues relevant to the development of safe emergency procedures where the use of SCBAs is warranted.

Validation of two running tests as estimates of maximal aerobic power in children.

In order to validate the "Maximal Multistage 20 Meter Shuttle Run Test" by Leger and Lambert (1982) (20-MST) as an estimate of maximal aerobic power (VO2max) and to compare the results of this test with the results of a 6 min endurance run, 82 subjects (41 boys and 41 girls) aged 12-14 performed the 20-MST and the 6 min endurance run, and had their VO2max directly measured during maximal treadmill running. The 20-MST is a maximal running test starting at a running speed of 8.0 km X h-1, which is increased every minute and in which the pace is set by an audio signal. Performing the test, one runs a 20-meter course back and forth. The test result is expressed as "palier" (one palier is approximately one minute). The mean results of the 20-MST were, for boys, 8.0 palier (+/- 1.7) and for girls, 6.4 palier (+/- 1.5). The mean results of the 6 min endurance run were for boys, 1264.4 meters (+/- 160.8), and for girls, 1103.9 meters (+/- 144.7). The mean VO2max for boys was 53.2 ml X kg-1 X min-1 (+/- 5.4) and for girls, 44.1 (+/- 4.8) ml X kg-1 X min-1. The correlation coefficient between VO2max and the 20-MST was found to be 0.68 (+/- 3.9) for boys, 0.69 (+/- 3.4) for girls and 0.76 (+/- 4.4) for both sexes, and that of VO2max with the 6 min endurance run was 0.51 (+/- 4.6) for boys, 0.45 (+/- 4.3) for girls and 0.63 (+/- 5.3) for both sexes. The conclusion is that the 20-MST is a suitable tool for the evaluation of maximal aerobic power. Although the differences in validity between the 20-MST and the 6 minutes endurance run were statistically not significant (p greater than 0.05), for reasons of practicability the 20-MST should be preferred to the 6 minutes endurance run when used in physical education classes.

Anaerobic metabolism of the respiratory muscles during exercise

Although minute ventilation (VE) exhibits marked increases during heavy rhythmic exercise utilizing a large muscle mass, the extent to which this hyperpnea stresses the respiratory muscles remains controversial. In an attempt to resolve this matter, we measured arterial blood lactate concentration during seated isocapnic reproduction of peak exercise ventilation. This level of ventilation had previously been identified during a maximal 2-min treadmill run. We found that maintenance of peak exercise ventilation raised blood lactate 50% in subjects otherwise at rest (N = 8, P less than 0.01). This lactate rise occurred despite addition of CO2 to inspired gas in amounts sufficient to maintain arterial blood pH and PCO2 at resting levels, which suggests that achieving the high exercise ventilation associated with VO2max may require significant anaerobic metabolism by respiratory muscles.

Physiological Characteristics of Champion Synchronized Swimmers

In brief: Data on body composition, metabolic responses to a maximal treadmill run, postexercise blood lactate, pulmonary function, flexibility, and isokinetic work were obtained in 13 champion synchronized swimmers. Metabolic responses to a maximal tethered swimming test were obtained on four of the subjects. The synchronized swimmers were similar to nonathletic women in percent fat(24.0) and were only slightly different in V o2 max(43.2 ml· kg−1-min−1). The postexercise blood lactate of 101.7 mg/100 ml was comparable to values reported for female competitive swimmers. Results suggest that success in synchronized swimming is not heavily dependent on aerobic capacity, although participants in solo and duet events tended to have higher Vo2 max values.

Salbutamol and treadmill performance in non-atopic athletes

Salbutamol and treadmill performance in non-atopic athletes. Med. Sci. Sports Exerc., Vol. 15, No. 6, pp. 520-522, 1983. Nineteen aerobic, non-atopic, athletes (10 females, 9 males) were studied in a double-blind fashion to determine the effect of a therapeutic dosage of salbutamol on pulmonary function, oxygen consumption (VO2max), heart rate (HR), and anaerobic threshold (AT). A placebo and salbutamol (in aerosol form) were administered in a dosage of two puffs four times per day. Forced vital capacity (FVC), FEV1.0, and mid-maximal expiratory flow were assessed prior to a maximal treadmill run, and at 5, 10, and 15 min of recovery. Resting and maximal HR, VO2max, AT, and VE were determined prior to and immediately after the 1-wk experimental period. Pre-test results showed no evidence of airway obstruction in any athlete. There was no significant change in any pulmonary function variable as a result of salbutamol administration. Maximal oxygen consumption showed a slight, nonsignificant (P greater than 0.05) decrease in both the salbutamol and placebo groups. There was also a similar nonsignificant decrease in pulmonary function in both groups. Resting and maximal HR and AT were unchanged. These results indicate that therapeutic administration of a selective beta-2 agonist does not affect pulmonary function or performance-related variables in non-atopic elite athletes.

A comparison of the training responses to aerobic dance and jogging in college females

The purpose of this study was to compare the physiological alterations that occur in college females as a result of a 7-wk jogging and aerobic dance-training program. Forty-six subjects (18-29 yr) volunteered to participate and included 15 dancers, 19 joggers, and 12 controls. All subjects were given a pre- and post-VO2max treadmill test. The joggers and dancers trained 4 d/wk, 30 min/d for 7 wk at an intensity that represented approximately 83 and 84% of their initial maximal heart rates, respectively. Both experimental groups significantly (P less than 0.05) increased their VO2max, VEmax, and maximal treadmill running times and significantly (P less than 0.05) decreased their maximal heart rates as a result of the training. The control group showed no significant (P greater than 0.05) changes in any of the variables measured. It was concluded that both aerobic dance and jogging were equally effective (P less than 0.05) exercise modalities for improving cardiorespiratory endurance when performed at similar intensities, frequencies, and durations.