Percentage Of VO2max Research Articles

ACE GENE POLYMORPHISM AND EXERCISE TRAINING-INDUCED CHANGES IN SODIUM EXCRETION IN AFRICAN AMERICAN HYPERTENSIVES

We sought to determine whether the changes in urinary NA+ excretion in response to shortterm exercise training were associated with the angiotensin converting enzyme (ACE) gene polymorphism. Subjects (n = 13; age 51 ± 8 yrs) were obese (body fat > 35%), sedentary (VO2max 21.8 ± 4.8 ml/kg/min), hypertensive (BP 143 ± 3 / 91 ± 2 mmHg) male and female African Americans. The insertion/deletion ACE gene (II, n = 5; ID, n = 4; DD, n = 4) polymorphism was determined using standard PCR procedures. Exercise consisted of 7 consecutive days of treadmill walking and stationary cycling for 50 min/d at 65% of heart rate reserve. Na+ excretion was determined by 24-hour urine collection at baseline and beginning 14–18 hours after the last exercise session. Subjects consumed diets identical in macronutrient and Na+ content during the testing periods. Baseline Na+ excretion, fasting insulin and glucose levels, percent body fat, VO2max, and casual mean blood pressure (MBP) were similar in the ACE genotype groups. After seven days of exercise training, Na+ excretion was significantly increased in the II (119 ± 26 vs 186 ± 42 mmol/d, p = 0.03), ID (102 ± 16 vs 125 ± 13 mmol/d, p = 0.043), and DD (138 ± 11 vs 160 ± 12 mmol/d, p = 0.024) genotype groups. The increase in Na+ excretion in response to short-term exercise training tended to be higher in the II (57%) genotype group compared to the ID (23%) and DD (16%) genotype groups (p = 0.079). Fasting insulin levels were significantly decreased in the II (8 ± 1 vs 5 ± 1 uU/ml, p = 0.018) genotype group but not in the ID (10 ± 3 vs 6 ± 1 uU/ml, p = 0.134) and DD (12 ± 3 vs 11 ± 3 uU/ml, p = 0.608) genotype groups. MBP was significantly reduced only in the DD genotype group (113 ± 1 vs 110 ± 2 mmHg, p = 0.016). These preliminary results suggest that the ACE gene polymorphism is associated with short-term exercise training-induced Na+ excretion and this effect may be related to changes in fasting insulin levels. Supported by NIH NCRR/GCRC 01RR00056, NIA AG 12781, and NHLBI HL54526

Insulin sensitivity in postmenopausal women: independent and combined associations with hormone replacement, cardiovascular fitness, and body composition.

The effects of combined physical activity and hormone replacement therapy (HRT) on insulin sensitivity in postmenopausal (PM) women are unclear. The purpose of the study was to test the following hypotheses: 1) PM women who have undergone vigorous exercise training have greater insulin sensitivity than PM women who are physically active and PM women who are sedentary, and 2) PM women using HRT have greater insulin sensitivity than PM women not using HRT. We also sought to determine whether body composition or cardiovascular fitness was the stronger predictor of insulin sensitivity in these women. Three groups of PM women classified as sedentary (n = 18), physically active (n = 19), and athletic (n = 23) underwent an insulin-modified frequently sampled intravenous glucose tolerance test to determine the insulin sensitivity index (SI) and dual-energy X-ray absorptiometry to determine body composition. There was a significant association between both physical activity (P = 0.036) and HRT (P = 0.007) and fasting plasma insulin levels. The athletic PM women had the lowest plasma insulin levels and the highest SI. Across all physical activity levels, PM women using HRT (n = 29) had significantly lower fasting plasma insulin levels and a lower SI than PM women not using HRT (n = 31). HRT was significantly (P = 0.025) associated with intravenous glucose tolerance (KG); the women not using HRT had a higher K(G); than the PM women using HRT (0.83 +/- 0.08 vs. 0.60 +/- 0.05% per minute). Percent body fat (r = -0.37, P = 0.004) and VO2max (r = 0.35, P = 0.007) were similar predictors of SI. We conclude that, although overall HRT was associated with an attenuated SI, vigorous exercise training was independently associated with the greatest SI. In addition, PM women using HRT may benefit from having lower plasma insulin levels, but they may also have a lower SI.

Work situation and physical workload of refuse collectors in three different time periods

City officials from Haarlem, a Dutch city in which one of the first scientific studies on the workload of refuse collectors was performed, wanted to compare the work situation and physical workload in 1997 with the results of a study performed in Haarlem in 1985 and with the results of a national study conducted in 1993 . Depending on the results, they wanted to implement effective preventive measures. The present study consisted of a field study, a simulation experiment in the laboratory, and a questionnaire concerning work characteristics and health effects among 18 refuse collectors. The work situation and the energetic workload were not more favourable in Haarlem in 1997 compared to Haarlem of 1985 or the national study conducted in 1993. On several important parameters, such as the time carrying plastic bags or pushing containers, amount of refuse collected and percentage VO 2max during a working day, the results in the present study did not differ from those in earlier studies. However, the working postures and the perceived exertion of the refuse collectors in Haarlem in 1997 were more favourable when compared to the refuse collectors in the national study. The results have convinced the management to plan an intervention study of potentially effective measures to improve the work situation and to reduce the physical workload. Planned measures are the introduction of job rotation, an effective work–rest schedule and the redesign of two-wheeled containers. Relevance to industry This study shows that a comparison of the work situation and physical workload with former studies is an effective way to address the issue of preventive measures.

Fat metabolism during high-intensity exercise in endurance-trained and untrained men

To determine whether trained individuals rely more on fat than untrained persons during high-intensity exercise, six endurance-trained men and six untrained men were studied during 30 minutes of exercise at 75% to 80% maximal oxygen consumption (VO2max). The rates of appearance (Ra) and disappearance (Rd) of glycerol and free fatty acids (FFAs) were determined using [1,1,2,3,3-2H]glycerol and [1-13C]palmitate, respectively, whereas the overall rate of fatty acid oxidation was determined using indirect calorimetry. During exercise, the whole-body rate of lipolysis (ie, glycerol Ra) was higher in the trained group (7.1 +/- 1.2 v 4.5 +/- 0.7 micromol x min(-1) x kg(-1), P < .05), as was the Ra (approximately Rd) of FFA (9.0 +/- 0.9 v 5.0 +/- 1.0 micromol x min(-1) x kg(-1), P < .001). FFA utilization was higher in trained subjects even when expressed as a percentage of total energy expenditure (10% +/- 1% v 7% +/- 1%, P < .05). However, this difference in plasma FFA flux could not account for all of the difference in fatty acid oxidation between trained and untrained subjects (20.8 +/- 3.3 v 7.9 +/- 1.6 micromol x min(-1) x kg(-1), or 23% +/- 3% v 13% +/- 2% of total energy expenditure, both P < .05). Thus, the oxidation of fatty acids derived from some other source also must have been greater in the trained men. We conclude that trained athletes use more fat than untrained individuals even during intense exercise performed at the same percentage of VO2max. The additional fatty acids appear to be derived from both adipose tissue and, presumably, intramuscular triglyceride stores.

Specificity of treadmill and cycle ergometer tests in triathletes, runners and cyclists.

The objective of this study was to evaluate the viability of using a single test in which cardiorespiratory variables are measured, to establish training guidelines in running and/or cycling training activities. Six triathletes (two females and four males), six runners (two females and four males) and six males cyclists, all with 5.5 years of serious training and still involved in racing, were tested on a treadmill and cycle ergometer. Cardiorespiratory variables [e.g., heart rate (HR), minute ventilation, carbon dioxide output (VCO2)] were calculated relative to fixed percentages of maximal oxygen uptake (VO2max; from 50 to 100%). The entire group of subjects had significantly (P < 0.05) higher values of VO2max on the treadmill compared with the cycle ergometer [mean (SEM) 4.7 (0.8) and 4.4 (0.9) l.min-1, respectively], and differences between tests averaged 10.5% for runners, 6.1% for triathletes and 2.8% for cyclists. A three-way analysis of variance using a 3 x 2 x 6 design (groups x tests x intensities) demonstrated that all factors yielded highly significant F-ratios (P < 0.05) for all variables between tests, even though differences in HR were only 4 beats.min-1. When HR was plotted against a fixed percentage of VO2max, a high correlation was found between tests. These results demonstrate that for triathletes, cyclists and runners, the relationship between HR and percentage of VO2max, obtained in either a treadmill or a cycle ergometer test, may be used independently of absolute VO2max to obtain reference HR values that can be used to monitor their running and/or cycling training bouts.

Exercise gas exchange responses in the differentiation of pathologic and physiologic left ventricular hypertrophy.

The purpose of the present investigation was to examine differences that may exist in maximal and submaximal exercise gas exchange parameters and their use in differentiating pathological and physiological left ventricular hypertrophy. Exercise gas exchange responses were measured on-line during a maximal ramping cycle-ergometer exercise test in 10 young, male hypertrophic cardiomyopathy (HCM) patients, 11 elite triathletes, and 9 normal controls. The HCM patients exhibited significantly lower VO2max, anaerobic threshold (AT) in both absolute terms (ATVO2) and as a percentage of VO2max (AT%VO2max), and oxygen-pulse (O2-pulse) compared with triathletes and normal controls. Elite triathletes exhibited significantly increased VO2max, %VO2max, ATVO2, AT%VO2max and O2-pulse compared with controls. The VE/VCO2 at AT was significantly increased in the HCM patients compared with triathletes and controls, whereas no difference was observed between triathletes and controls. Maximal and submaximal exercise gas exchange responses may be used as an additional noninvasive tool in the differential diagnosis of physiologic and pathologic left ventricular hypertrophy.

INFLUENCE OF CARBOHYDRATE INGESTION ON PHYSICAL AND MENTAL FUNCTION DURING INTERMITTENT HIGH-INTENSITY EXERCISE TO FATIGUE

484 This study was designed to determine the effects of carbohydrate supplementation on physical and mental tasks associated with the performance of intermittent high-intensity (IHI) exercise similar to many common competitive sporting events. Physically active men (n=5) and women (n=5), experienced in sports such as soccer/basketball completed 3 practice sessions and 2 experimental trials of an IHI shuttle running protocol designed to closely mimic the demands of an actual competitive sporting event such as basketball. The experimental sessions consisted of four 15 min quarters (QTR) of intermittent shuttle running at various percentages of VO2max (walking, jogging, running, sprinting and jumping) separated by a 20 min half time rest period and followed by a shuttle run to fatigue. Various tests of physical (shuttle run to fatigue, 20 meter maximal sprint, and 10 repetition maximal vertical jumping) and mental function (whole body motor skill test (MS-test), profile of mood states (POMS) and Stroop color-word test) were performed throughout the experimental trial. Carbohydrate (CHO) or Placebo (P) drinks were consumed prior to exercise (5 ml/kg; 6% soln) and at half time (18% soln). Smaller volumes (3 ml/kg) were given following QTR-1, Half, QTR-3, and QTR-4. Results: CHO supplementation resulted in a 37% longer run time to fatigue, and faster 20 m sprint times during QTR-4 (p<0.05). In addition, MS-test performance was improved with CHO ingestion and perception of fatigue (subscale of POMS) was decreased (p<0.05). These results suggest a beneficial role of CHO supplementation on physical as well as mental performance tasks that are similar to the demands of many common competitive sporting events involving intermittent high-intensity exercise. Supported by Gatorade Sports Science Institute

PERFORMANCE IS AFFECTED BY PROPER PLACEMENT OF TRAINING VOLUME DURING TAPERING

387 This study examined the effects of training volume placement during tapering on simulated 20 km time trial (20TT) performance. Eleven experienced cyclists (VO2max=4.20 L.min−1; 60.8 ml.kg−1.min−1) performed an incremental cycle ergometer test to exhaustion on day-1 and a simulated 20TT on day-2, before and after a 7-day taper. Following 4-weeks baseline training (4d per week × 60 min per session), the cyclists were randomly assigned to 3 taper protocols in which training volume (i.e. duration) was reduced by 30 (T30, n=5), 50 (T50, n=6) or 80 percent (T80, n=6) of baseline volume in a systematic fashion. Training intensity during tapering was maintained at 85 percent VO2max in all groups. Respiratory and metabolic measures (VE, VO2, VCO2, HR, RER) were collected every 5 km during the 20TT, and continuously during the incremental test and then averaged every 20 sec. The results showed a significant improvement in simulated 20TT performance time (26:18±1:31 to 25:04±1:36) in the T50 protocol only; as well, rating perceived exertion (p=0.03) and HR (p=0.08) were increased. No other physiological variables examined were significantly different before or after tapering, which was most likely due to the limited sample size. However, these results suggest that a minimal (T30) or an extensive (T80) reduction in training volume during the taper can have a significant affect on performance. This confirms the need for proper placement of training volume during tapering, and, that a systematic reduction in training volume is needed to elicit performance gains. Support: Sport Canada; Malaspina University-College

Age-Associated Alteration of Muscle Oxygenation Measured by Near Infrared Spectroscopy During Exercise

The influence of ageing on the capacity to increase muscle oxygen delivery during exercise is unclear. This was investigated by comparing the evolution of Near InfraRed Spectroscopy (NIRS) in 10 old (67 ± 5 years, Old group) and 13 young subjects (27 ± 4 years, Young group), during a progressive maximal exercise. The NIRS probe was placed on the vastus lateralis; muscle oxygen saturation – IR-SmO 2 – values were expressed on a scale using an arterial occlusion as the lower reference point and the subsequent reactive hyperaemia as the upper reference point. Resting IR-SmO 2 was found to be significantly lower in the Old as compared to the Young group. During exercise, VO 2 increased similarly as a function of the workload whereas IR-SmO 2 decreased faster in old subjects than in young ones. Conversely, when expressed at the same percentage of VO 2max, IR-SmO 2 followed a similar evolution in both groups from rest to maximal exercise (27.3 ± 16.7 vs 24.3 ± 12.9% decrease, in Old and Young group, respectively, NS). Thus, the initial difference remained constant between the two groups. During recovery, the time to recover the signal variation was not different between the two groups. We concluded that Old subjects demonstrate a systematic lower muscle oxygen saturation than Young ones. This difference could be explained by an age related decrease in muscle blood flow limiting O 2 supply.

The Importance of Physical Fitness In the Performance of Adequate Cardiopulmonary Resuscitation

The aim of the present investigation was to evaluate the influence of the physical fitness of a cardiopulmonary resuscitation (CPR) provider on the performance of and physiologic response to CPR. To this end, comparisons were made of sedentary and physically active subjects in terms of CPR performance and physiologic variables. Two study groups were established: group P (n=14), composed of sedentary, professional CPR rescuers (mean [+/-SD]; age, 34+/-6 years; VO2max, 32.5+/-5.5 mL/kg/min), and group Ex (n=14), composed of physically active, nonexperienced subjects (age, 34+/-6 years; VO2max, 44.5+/-8.5 mL/kg/min). Each subject was required to perform an 18-min CPR session, which involved manual external cardiac compressions (ECCs) on an electronic teaching mannequin following accepted standard CPR guidelines. Subjects' gas exchange parameters and heart rates (HRs) were monitored throughout the trial. Variables indicating the adequacy of the ECCs (ECC depth and the percentage of incorrect compressions and hand placements) also were determined. Overall CPR performance was similar in both groups. The indicators of ECC adequacy fell within accepted limits (ie, an ECC depth between 38 and 51 mm). However, fatigue prevented four subjects from group P from completing the trial. In contrast, the physiologic responses to CPR differed between groups. The indicators of the intensity of effort during the trial, such as HR or percentage of maximum oxygen uptake (VO2max) were higher in group P subjects than group Ex subjects, respectively (HRs at the end of the trial, 139+/-22 vs 115+/-17 beats/min, p < 0.01; percentage of VO2max after 12 min of CPR, 46.7+/-9.7% vs 37.2+/-10.4%, p < 0.05). These results suggest that a certain level of physical fitness may be beneficial to CPR providers to ensure the adequacy of chest compressions performed during relatively long periods of cardiac arrest.

PROGRESS REPORTS; A METHOD FOR ADJUSTING INDIVIDUALIZED EXERCISE PRESCRIPTIONS

528 Ball State University's Adult Physical Fitness Program (APFP) has developed a progress report protocol to summarize physiological changes that occurred during exercise training, to document exercise adherence, and to update exercise prescription for members of the APFP. The progress reporting protocol is designed to perform an assessment for members biannually and typically involves several steps. The protocol begins with a review of exercise frequency, intensity, duration, attendance and weekly energy expenditure estimates. Resistance training information including the number of repetitions, sets and average weight lifted during each exercise is also reviewed. Members are then scheduled for an assessment in the APFP fitness center on the exercise mode of their choice. Body weight, resting heart rate and blood pressure are measured prior to the assessment. After a three minute warm-up, measurements are performed during two stages (i.e. 60 and 80% of maximal oxygen uptake) (VO2max). Percentages of VO2max are determined during a graded exercise test (GXT) when the member joins the APFP. Values collected during the assessment are then compared to values from the same relative exercise intensity during the GXT. Exercise leaders review the assessment and provide copies of the results including a short narrative and graphs to document significant physiological changes. Exercise leaders meet individually with members and solicit feedback concerning program operations and to establish new fitness goals. Based on the data and goals of the member, exercise leaders adjust the exercise prescription to achieve those goals.

Prescribing exercise intensity for older women.

For the purpose of prescribing exercise intensity, the American College of Sports Medicine (ACSM) provides guidelines for relating the perceived level of exertion and the heart rate (HR) response during exercise, expressed either as a percentage of maximal HR or of HR reserve, to a percentage of maximal aerobic power (VO2max). However, because maximal HR and VO2max decline with age, it is possible that these guidelines are not appropriate for an older population. The purpose of this study was to evaluate in 60- to 72-year-old women the relationships among the common methods of prescribing exercise intensity. Participants were 112 healthy but sedentary women, aged 66 +/- 4 years, who performed treadmill walking at four speeds. Subjects were recruited from the community, and exercise tests were performed at a university laboratory facility. VO2max and maximal HR were determined during treadmill walking. The HR and VO2 responses to walking 6 minutes at each of four speeds ranging from 67 to 107 m/min, along with ratings of perceived exertion (RPE) and plasma lactate levels, were determined on a separate day. The exercise bouts required an average of 55 +/- 10%, 64 +/- 12%, 77 +/- 12%, and 91 +/- 9% of VO2max. Corresponding HR values were 64 +/- 8%, 70 +/- 9%, 81 +/- 10%, and 92 +/- 7% of maximal HR, and they were within the expected ranges based on ACSM guidelines. HR values as a percentage of HR reserve were much lower than expected based on the guidelines. RPE values were lower than expected at a given %VO2max, and plasma lactate levels were also relatively low, suggesting that older women are able to exercise at a higher percentage of VO2max than levels currently recommended. The results indicate that HR expressed as a percentage of maximal HR is an appropriate method of prescribing exercise intensity in healthy, sedentary 60- to 72-year-old women. The HR reserve method is not recommended in this population because it will likely result in the exercise being performed at a higher than expected percentage of VO2max.

Blood Lactate Responses to Exercise in Children: Part 2. Lactate Threshold

Part 2 reviews the literature concerning the lactate threshold in children. An analysis is presented comparing children to adults regarding responses to submaximal exercise, and the lactate threshold as a percentage of VO2max. Possible explanations for lower blood lactate concentrations during submaximal exercise in children are considered.

Effect of cycling experience, aerobic power, and power output on preferred and most economical cycling cadences.

To determine the effects of cycling experience, fitness level, and power output on preferred and most economical cycling cadences: 1) the preferred cadence (PC) of 12 male cyclists, 10 male runners, and 10 less-trained male noncyclists was determined at 75, 100, 150, 200, and 250 W for cyclists and runners and 75, 100, 125, 150, and 175 W for the less-trained group; and 2) steady-state aerobic demand was determined at six cadences (50, 65, 80, 95, 110 rpm and PC) at 100, 150, and 200 W for cyclists and runners and 75, 100, and 150 W for less-trained subjects. Cyclists and runners (VO2max: 70.7 +/- 4.1 and 72.5 +/- 2.2 mL.kg-1.min-1, respectively) maintained PC between 90 and 100 rpm at all power outputs and both groups selected similar cadences at each power output. In contrast, the less-trained group (VO2max = 44.2 +/- 2.8 mL.kg-1.min-1) selected lower cadences at all common power outputs and reduced cadence from approximately 80 rpm at 75 W to 65 rpm at 175 W. The preferred cadences of all groups were significantly higher than their respective most economical cadences at all power outputs. Changes in power output had little effect on the most economical cadence, which was between 53.3 and 59.9 rpm, in all groups. It was concluded that cycling experience and minimization of aerobic demand are not critical determinants of PC in well-trained individuals. It was speculated that less-trained noncyclists, who cycled at a higher percentage of VO2max, may have selected lower PC to reduce aerobic demand.

Dangerous Curves: A Perspective on Exercise, Lactate, and the Anaerobic Threshold

A number of general observations can be made from these recent studies. Lactate is a ubiquitous substance that is produced and removed from the body at all times, even at rest, both with and without the availability of oxygen. It is now recognized that lactate accumulates in the blood for several reasons, not just the fact that oxygen supply to the muscle is inadequate. Lactate production and removal is a continuous process; it is a change in the rate of one or the other that determines the blood lactate level. Rather than a specific threshold, there is most likely a period of time during which lactate production begins to exceed the body's capacity to remove it (through buffering or oxidation in other fibers). It may be appropriate to replace the term "anaerobic threshold" to a more functional description, since the muscles are never entirely anaerobic nor is there always a distinct threshold ("oxygen independent glycolysis" among others has been suggested) Lactate plays a major role as a metabolic substrate during exercise, is the preferred fuel for slow-twitch muscle fibers, and is a precursor for liver gluconeogenesis. The point at which lactate begins to accumulate in the blood, causing an increase in ventilation, is important to document clinically. Irrespective of the underlying mechanism or specific model that describes the process, the physiologic changes associated with lactate accumulation have significant import for cardiopulmonary performance. These include metabolic acidosis, impaired muscle contraction, hyperventilation, and altered oxygen kinetics, all of which contribute to an impaired capacity to perform work. Thus, any delay in the accumulation of blood lactate which can be attributed to an intervention (drug, exercise training, surgical, etc) may add important information concerning the efficacy of the intervention. A substantial body of evidence is available demonstrating that lactate accumulation occurs later (shifting to a higher percentage of Vo2max) after a period of endurance training. In athletes, the level of work that can be sustained prior to lactate accumulation, visually determined, is an accurate predictor of endurance performance. Presumably, these concepts have implications related to vocation/disability among patients with cardiovascular and pulmonary disease, but few such applied studies have been performed outside the laboratory. Blood lactate during exercise and its associated ventilatory changes maintain useful and interesting applications in both the clinical exercise laboratory and the sport sciences. However, the mechanism, interpretation, and application of these changes continue to rely more on tradition and convenience than science.

Physical and physiological factors associated with success in the triathlon.

The physiological demands of sequential exercise in swimming, cycling and running are unique and require the triathlete to develop physical and physiological characteristics that are a blend of those seen in endurance swimming, cycling and running specialists. Elite triathletes are generally tall, of average to light weight and have low levels of body fat, a physique which provides the advantages of large leverage and an optimal power to surface area or weight ratio. Triathletes have high maximum oxygen uptake (VO2max) values, but VO2max may be on average marginally lower than values previously observed in endurance specialists. Although VO2max is a predictor of performance in triathletes of mixed abilities, it cannot be used to predict performance within homogenous groups of elite performers. Nevertheless, elite triathletes have significantly higher VO2max values than sub-elite triathletes and high VO2max levels are required for success in triathlons. The ability of the triathlete to exercise at a lower percentage of VO2max for a given submaximal workload may be especially important to triathlon success. This is influenced not only by VO2max itself, but also by anaerobic threshold and economy of movement. Anaerobic threshold, as indicated by either ventilatory threshold or lactate threshold, improves with triathlon training and when measured in the appropriate exercise mode has been related to swim, cycle and run performance in the triathlon. Economy of movement in swimming, cycling and running is also related to triathlon performance, and swimming economy in particular appears to be an area where triathletes could make large improvements. Future research should utilise experimental methodologies to investigate triathlon physiology, in particular, the influence of sequential exercise in different exercise modes on physiological function and examine the influence of different training interventions on triathlon physiology and performance.

COMPARISON OF% HEART RATE RESERVE WITH%VO2max AND%VO2 RESERVE95

For exercise prescription, the ACSM assumes that% heart rate reserve (%HRR) is equivalent to%VO2max. We hypothesized that%HRR is not equivalent to%VO2max, but rather to%VO2 reserve (%VO2R), i.e. a percentage of VO2max - VO2rest. In the current investigation, 33 males and 30 females, age 28 ± 1 yr (mean ± SE), were exercised to volitional exhaustion on an incremental cycle ergometer test in 3 minute stages. For each subject, data obtained at rest, at the end of each stage, and at maximum were used to determine linear regressions of%HRR vs%VO2max and of%HRR vs%VO2R. The mean regressions were:Table For%HRR vs%VO2max, the intercept and slope were significantly different (p < 0.001) from 0 and 1, respectively. For%HRR vs%VO2R, the regression line was not distinguishable from the line of identity. There was a significant (p < 0.01) relationship between fitness level and the discrepancy between%HRR and%VO2max. Those subjects with lower VO2max's had a greater discrepancy. In conclusion,%HRR should be considered equivalent to%VO2R, not to%VO2max.

Relationship of Blood Lactate to Selected Physiological Variables during the I-Mile Walk Test with Elderly 97

The purpose of this investigation was to examine the relationship of selected physiologic variables to lactate accumulation at the end of a 1 Mile Walk Test (I-MWT) in an elderly population. 30 Older adults(7M&23F)(Mean age [±SD]: 64±7)(VO2max 22±4) voluntered to participate in the study. Physiologic date were obtained by using a Cosmed K2 miniaturized 02 analyzer with telemetric capabilities during a maximal treadmill (TM) test, and I-MWT. Blood samples were obtained from the ear lobe for lactate analysis immediately prior to the I-MWT and at the completion of the test. The following correlation coefficients were obtained: r=.329 between lactate and VO2 used during the walk, r=.063 between lactate and percent of VO2max used during the walk, r=.126 between lactate and percent of HRmax used during the walk, r=.65 (p<.05)between lactate and HR used during the walk, r=.40 between lactate and I-MWT, and r=.09 between lactate and RPE. The data suggest that the correlation among lactate production and other physiological variables is in the range of low to moderate in older population. These findings should be considered when physical training programs are based on the blood lactate response to exercise.

The relative influence of body characteristics on humid heat stress response.

The present study was designed to determine the relative importance of individual characteristics such as maximal oxygen uptake (VO2max), adiposity, DuBois body surface area (AD), surface to mass ratio (AD: mass) and body mass, for the individual's reaction to humid heat stress. For this purpose 27 subjects (19 men, 8 women), with heterogeneous characteristics (VO2max 1.86-5.28 1.min-1; fat% 8.0%-31.9%; mass 49.8-102.1 kg; AD 1.52-2.33 m2) first rested (30 min) and then exercised (60 W for 1 h) on a cycle ergometer in a warm humid climate (35 degrees C, 80% relative humidity). Their physiological responses at the end of exercise were analysed to assess their relationship with individual characteristics using a stepwise multiple regression technique. Dependent variables (with ranges) included final values of rectal temperature (Tre 37.5-39.0 degrees C), mean skin temperature (Tsk 35.7-37.5 degrees C), body heat storage (S 3.2-8.1 J.g-1), heart rate (HR 100-172 beat.min-1), sweat loss (397-1403 g), mean arterial blood pressure (BPa, 68-96 mmHg), forearm blood flow (FBF, 10.1-33.9 ml.100ml-1.min-1) and forearm vascular conductance (FVC = FBF/BPa, 0.11-0.49 ml.100ml-1.min-1.mmHg-1). The Tre, Tsk and S were (34%-65%) determined in the main by VO2max or by exercise intensity expressed as a percentage of VO2max (% VO2max). For Tre, AD: mass ratio also contributed to the variance explained, with about half the effect of VO2max. For Tsk, fat% contributed to the variance explained with about two-third the effect of VO2max. Total body sweat loss was highly dependent (50%) on body size (AD or mass) with regular activity level having a quarter of the effect of body size on sweat loss. The HR, similar to Tre, was determined by VO2max (48%-51%), with less than half the effect of AD or AD:mass (20%). Other circulatory parameters (FBF, BPa, FVC) showed little relationship with individual characteristics (< 36% of variance explained). In general, the higher the VO2max and/or the bigger the subject, the lower the heat strain observed. The widely accepted concept, that body core temperature is determined by exercise intensity expressed as % VO2max and sweat loss by absolute heat load, was only partially supported by the results. For both variables, other individual characteristics were also shown to contribute.

Normal cardiopulmonary responses during incremental exercise in 20??? to 70-yr-old men

Healthy men (N = 1424, age 20-70 yr) underwent a progressive incremental treadmill exercise test to volitional maximum. Cardiopulmonary variables were measured breath-by-breath. The aerobic power (VO2max) declined at an average yearly rate of 0.33 ml.kg.-1min-1, HRmax declined 0.685 beats.min-1.yr-1, and max O2 pulse declined at an annual rate of 0.115 ml.beat-1.kg-1*100. Gas exchange threshold (GET) expressed as percentage of VO2max was 58% and 69% in the youngest (20-30 yr) and oldest (61-70 yr) decades, respectively. The average decline in VE, Vt, f, and PETCO2 over the entire age range was 29%, 10%, 21%, and 7%, respectively. There were increases in VE/VO2, and VE/VECO2, from age 20-70 yr of 13% and 14%, respectively, but no changes across 5 decades in PETO2. Physical (height and weight) as well as life-style characteristics (leisure time activity, place of residency, smoking), were found to be potent predictors in most of the cardiopulmonary values at maximal exercise and therefore should be incorporated in the predictive equations for such variables. Normal response patterns of most cardiopulmonary variables throughout the range of exercise intensities were shown to be age-affected and thus should be standardized for age decades.