Submaximal Trials Research Articles

Effects of swimming with a wet suit on energy expenditure during subsequent cycling

The aim of this study was to investigate the effects of swimming with a wetsuit on energy expenditure during subsequent cycling. Nine well-trained triathletes underwent three submaximal trials. The first trial (SC) consisted of a 750-m swim realised at a competition pace, followed by a 10-min cycling exercise at a power output corresponding to the ventilatory threshold . The two other trials were composed of the same cycling exercise, preceded either by a 750-m swim with a wetsuit (WSC) or by a cycling warm-up (Ctrl). The main results are that the WSC trial was characterised by significantly lower swimming cadence (-14%), heart rate (-11%), and lactate values (-47%) compared to the SC trial, p < 0.05. Moreover, cycling efficiency was significantly higher in the WSC trial compared to the SC trial (12.1% difference, p < 0.05). The lower relative intensity observed during swimming with a wetsuit suggest the relative importance of swimming condition on the total performance in a sprint triathlon.

PERCEIVED EFFORT IN UNILATERAL AND BILATERAL ISOMETRIC EXERTIONS

Subjects produce larger unilateral forces than bilateral forces for the same perceived submaximal effort. This submaximal bilateral deficit has been attributed to physiological and perceptual components. PURPOSE To examine the perceived effort of unilateral and bilateral exertions when absolute force was held constant. METHODS Forty-two healthy subjects (22.8±3.5 yrs. 171.0±26.4 cm, 69.4±10.7 kg) without upper extremity injury performed three 3-second trials each of bilateral (B), unilateral dominant (UD) and non-dominant (UN) elbow flexion at 100%, 80%, 60%, 40%, and 20% of maximal effort. Subjects matched force production to a target force using visual feedback from a realtime display. Subjects indicated perceived effort for that trial using a standardized measurement scale. RESULTS The mean coefficient of variation of force for maximal effort trials ranged from 4.8–5.8% and 1.6–2.3% for submaximal effort trials. The bilateral index at 100% effort (−8.6±5.6%) was significantly less than zero but was small (< 1%) for submaximal trials. Unilaterally, subjects matched the target force of 80% maximum effort most closely (79.6±10.9% and 79.0±7.9%, UD and UN, respectively). At the 60% target force subjects slightly overestimated the effort they were producing in UD and UN (63.7±9.2% and 62.1±8.8%, respectively). This overestimation increased at the 40% and 20% target forces in UD and UN (47.1±9.6%, 46.5±7.6%, 27.8±11.5%, and 26.0±11.3%, respectively). The perception of effort in bilateral trials was consistently and significantly (p < 0.01) higher than recorded in unilateral trials. Perceived effort at 80% and 60% target force was 7.9–9.6% higher in bilateral trials than unilateral trials (87.2±8.1% and 71.6±9.1%, respectively). The elevated perception of effort in bilateral trials was slightly less at the 40% and 20% target forces but still ranged from 5.5–7.2% higher than in unilateral trials (52.6±9.7% and 33.3±10.4%, respectively). CONCLUSION Force production was perceived to be more strenuous when performed bilaterally suggesting that the submaximal bilateral deficit contains a perceptual component.

ACUTE EFFECTS OF TRANS-10,CIS-12 CONJUGATED LINOLEIC ACID CONSUMPTION ON FUEL USE

Chronic consumption of a mixture of conjugated linoleic acid isomers reduces body fat deposition. Acute ingestion apparently enhances metabolic rate and fatty acid oxidation in animal models. Recent research suggests that effects on lipid metabolism are due primarily to the trans-10, cis-12 isomer of CLA (10, 12CLA). PURPOSE To examine the effects of acute oral 10,12CLA on resting and exercise metabolic rate and fuel use in humans. METHODS Thirteen 18–25y, healthy, untrained males underwent baseline VO2peak testing. Fasted subjects consumed 4.8g of 10,12CLA (EXP) or an olive oil placebo on four different occasions (two resting, two submaximal exercise trials for 40 min at 60% VO2peak). For each of these trials, four blood samples (10 subjects) and measures of metabolic rate (indirect calorimetry) and respiratory quotient (RQ) were measured in 10 min segments (prior, 80, 110, and 140 min post supplement ingestion). Exercise began 80 min post ingestion for exercise trials. Blood was analyzed for glucose, glycerol, and fatty acids. RESULTS For resting trials, serum 10,12CLA was significantly higher by 80 min post ingestion (0.38±0.19 μ g/ml) compared to baseline (0.0 μ g/ml) with a peak at 140 min (10.10±2.50 μ g/ml,p < 0.05). Four subjects showed no change in serum 10,12CLA during exercise EXP trials. Those who responded during the exercise trial had a peak in serum 10,12CLA at 110 min (12.83 μ g/ml±3.3, p < 0.05) which decreased to 9.09 μ g/ml ± 3.3 by 140 min. There was no effect of supplement on RQ at rest while there was a trend for a more rapid drop in RQ during exercise in EXP(p = .062). No significant differences between treatments were found for glucose, glycerol, resting or exercise metabolic rate for any time points. CONCLUSIONS At rest, 10,12CLA significantly rose in the blood by 80 min after ingestion of 4.8g. Exercise appeared to interfere with 10,12CLA absorption in some subjects. There was no significant effect of the supplement on indicators of lipolysis, fuel use, or metabolic rate at rest or during exercise.

The effect of hyperoxia on submaximal exercise with the self-contained breathing apparatus

The effects of hyperoxia on submaximal exercise with the self-contained breathing apparatus (SCBA) were studied in 25 males. Each participant completed a graded exercise test for the determination of ventilatory threshold (VT) and then a submaximal practice trial with a normoxic gas mixture. The normoxic (20.93 ± 0.22% O2 ; SUB21) and hyperoxic (40.18 ± 0.73% O2; SUB40) submaximal trials were then administered in a random order. All exercise tests were completed on separate days while wearing firefighting gear and the SCBA. Compared with SUB21, hyperoxia significantly reduced minute ventilation ([Vdot]E ), mask pressure (Pmask), heart rate, blood lactate concentration, perceived exertion, and perceived breathing distress. As expected, hemoglobin saturation remained higher (p<0.05) during SUB40. The reductions in both [Vdot]E and Pmask with hyperoxia imply a reduction in the work of breathing during exercise. Total gas consumption was 10.3 ± 8.1% lower during SUB40 when compared to SUB21, another finding that has significant practical implications for occupational safety.

Intratester reliability and measurement error of the adapted crossover hop for distance

Objective: To determine the intratester reliability of the adapted crossover hop for distance in uninjured subjects. Design: Within-subject between-session repeated measures with random selection from a sample of convenience. Setting: University physiotherapy laboratory. Participants: Twelve subjects (male:n=4; female: n=8; age=22·4±5·5 years; height=168·7±5·2cm; mass=65·8±8·5kg) without a history of lower limb or low back injury. Methods and Measures: Subjects performed three sub-maximal warm-up trials followed by three measured trials of the adapted crossover hop for distance utilising the self-reported dominant limb on two test sessions. The intraclass correlation coefficient (ICC) form (2,1), standard error of measurement (SEM), and 95% confidence interval (CI) were calculated utilising subjects' highest scores to determine intratester reliability and measurement precision. Results: The ICC (2,1) was 0·94. The SEM was 28·8cm. The 95% CI was 56·5cm. Conclusions: The results of this study demonstrate the adapted crossover hop for distance has high intratester reliability and acceptable measurement error in uninjured subjects. Thus, a new hop test with potential for identifying knee dysfunction in an anterior cruciate ligament (ACL)-injured population is presented. Future research should determine the reliability, measurement error, and validity of the adapted crossover hop for distance in an ACL-injured population.

POST EXERCISE METABOLIC RATE FOLLOWING DOWNHILL RUNNING

An acute eccentric exercise bout produces muscle damage and delayed onset muscle soreness (DOMS). Both are attenuated following a subsequent eccentric exercise bout indicating that an adaptation occurs. The degree to which this type of exercise influences recovery energy expenditure is unknown. PURPOSE: We investigated whether excess postexercise oxygen consumption (EPOC) measured for 2h and resting metabolic rate (RMR) measured 24h (day 2) and 48h (day 3) post-exercise would differ following level vs downhill treadmill running. METHODS: Eight untrained male subjects performed three 40min submaximal exercise trials eliciting ∼70% VO2max: a level running trial and two downhill running trials (DH1 and DH2). DH1 was performed 1wk after level, and DH2 2wk after DH1. Testing occurred in the morning following an overnight fast and no strenuous exercise for the previous 36h. Baseline RMR was measured for 30min pre-exercise. DOMS was rated for five lower body sites at 24h and 48h post exercise. Analyses included 1- and 2-way ANOVA and Friedman tests. RESULTS: When compared to baseline, VO2 was significantly elevated at 60 (p < .01) and 90min (p < .03) for DH1 and at 60min (p < .03) for DH2, whereas VO2 was not significantly elevated at any of these time points during the level trial. However, there was no significant difference in the accumulated 2h EPOC among trials (level = 7.04/5.32, DH1 = 8.55í4.12, and DH2 = 8.38í2.89 L). RMR was not significantly different among days or among trials. DH1 produced significantly greater DOMS than level running (p < .01) at all 5 sites. CONCLUSION: It can be concluded that the first bout of downhill running for 40min at a moderately high intensity, which produced a significant amount of DOMS, resulted in a prolonged EPOC (> 90min). However, an elevated metabolic rate was not detected 24 or 48th following exercise when DOMS was evident. In contrast, metabolic rate returned to the resting value within 1h after running on a level grade. The physiological mechanisms involved in producing a prolonged elevation in metabolic rate following downhill running remain to be elucidated.

The coefficient of variation as a measure of sincerity of effort of grip strength, part I: The statistical principle

The coefficient of variation (CV) is a widely used measure of sincerity of effort of grip strength despite contradictory research findings and lack of empirical support in the literature. The purpose of this study was to investigate whether the CV is an appropriate measure of sincerity of effort. One hundred forty-six uninjured volunteers underwent a series of grip strength tests. The mean, standard deviation (SD), and CV of repeated strength trials were calculated, and paired comparisons were conducted between maximal and submaximal efforts. While the mean of maximal trials was significantly greater, there were no differences in SD between maximal and submaximal trials. Therefore, the increased CV associated with submaximal effort was an artifact of reduced torque rather than an indicator of a true increase in variability. Consequently, the CV is not an appropriate measure of sincerity of effort of grip strength.

EFFECTS OF HELIUM-OXYGEN ON EXERCISE PERFORMANCE WITH THE SELF-CONTAINED BREATHING APPARATUS (SCBA)

The self-contained breathing apparatus has been shown to reduce maximal and submaximal work capacity due to increased breathing resistance at moderate to high ventiliation rates. The present study investigated the effects of a helium-oxygen gas on exercise performance when breathing through the SCBA. Fifteen male subject, dressed in protective firefighting gear, completed a graded exercise test (GXT) and a 30-minute submaximal trial (SUB) on a motor-driven treadmill with a control gas (NOX: 21% O2 79% N2) and a helium based gas with the same oxygen content (HE-OX: 21% O2, 79% He2). HE-OX signifcantly increased maximal oxygen uptake (VO2max) by 10.2%, maximal minute ventilation by 25.2%, and respiratory exchange ratio (RER) at the same maximal work rate. In addition, the magnitude of hemoglobin desaturation at peak exercise was reduced with HE-OX. These observations suggest the possibility of a ventilation-limitation to maximal exercise while breathing NOX with the SCBA, which is at least partially relieved with the HE-OX gas. At VO2max, inspiratory and expiratory mask pressures were reduced (P < 0.05) and expiratory times decreased with HE-OX, suggesting a reduction in the work of breathing. During submaximal exercise there were no significant differences in oxygen uptake, carbon dioxide output, hemoglobin desaturation, RER, minute ventilation, or inspiratory and expiratory times with HE-OX, however inspiratory and expiratory mask pressure were reduced (P < 0.05). Maximal inspiratory and expiratory mouth pressures were measured before and after each SUB trial. There was a significant reduction in both pressures after the NOX, but not HE-OX trial, which suggests that the latter gas mixture might attenuate respiratory muscle fatigue. The results of this experiment demonstrate that some of the negative effects of the SCBA on exercise capacity may be alleviated by altering the density of the gas mixture. Supported by the department of National Defence and Praxair

Exercise Induces a Change in Plasma Fibrinogen Concentration: Fact or Fiction?

This study examined the effect of exercise on plasma fibrinogen concentrations with simultaneous measurements of plasma volume changes. Eight moderately active males aged 26.6±3.6 years (mean±SD) completed maximal (VO 2max) and submaximal (75% VO 2max for 30 minutes) exercise trials separated by 7 days. Venous blood samples were obtained at rest, immediately postexercise, and following 30 minutes of recovery. Whole blood was analysed for haematocrit and haemoglobin, while citrated plasma was assayed for fibrinogen levels. Values of haematocrit and haemoglobin before and after exercise were utilised for the estimation of plasma volume changes. Plasma volume decreased ( p<0.05) immediately following both maximal (−17.7±5.1%) and submaximal (−14.3±4.1%) exercise. Exercise resulted in decreased plasma fibrinogen levels (maximal exercise: from 266.3±14.5 to 222.2±23.9 mg·dL −1; submaximal exercise: from 239.5±45.4 to 209.7±42.4 mg·dL −1) only when postexercise raw data were corrected for the contraction of plasma volume. It is concluded therefore that changes in plasma volume in response to exercise should be taken into account when interpreting exercise effects on plasma fibrinogen concentration.

Effect of grip span on maximal grip force and fatigue of flexor digitorum superficialis

The aim of this study was to investigate the effect of grip span on isometric grip force and fatigue of the flexor digitorum superficialis (FDS) muscle during sustained voluntary contractions at 60–65% of the maximal voluntary contraction (MVC). Eighteen subjects performed isometric, submaximal gripping contractions using a grip dynamometer at four different grip span settings while the pronated forearm rested on a horizontal surface. Maximal absolute grip force and median power frequency of FDS surface electromyography (EMG) during the submaximal trials were analyzed. Fatigue of FDS, as inferred from EMG frequency shifts, did not change as a function of grip size. However, middle grip sizes allowed for greater absolute forces than the small or large size. When contractions are at 60–65% MVC and the muscle is allowed to fatigue, however, grip size may be less influential than when maximal absolute force is required.

CARDIOVASCULAR RESPONSES TO COMBINED ARM AND LEG EXERCISE

644 The purpose of this study was to determine the physiological effects of varied arm and leg work during total body exercise. Fourteen subjects (7 males, 7 females; age = 22 ± 2 yrs; wt = 67.9 ± 12.8 kg) first completed a maximal leg cycling test (Wmax) then on separate days performed six submaximal exercise trials at 60% of leg cycling Wmax with total work output (WO) being distributed between the upper and lower body. All combined work incorporated synchronous cranking and cycling at 50 rev·min−1 using two Monarch cycle ergometers. Subjects completed 7 min of submaximal exercise using the following work ratios: 0/60 (0% arms/WO, all legs), 5/55 (8% arms/WO), 10/50 (17% arms/WO), 15/45 (25% arms/WO), 20/40 (33% arms/WO), 25/35 (42% arms/WO). Oxygen consumption (VO2), ventilation (VE), heart rate (HR) and respiratory exchange ratio (RER) were continuously monitored using open circuit spirometry. A rating of perceived exertion (RPE) was attained after each trial. MANOVA with repeated measures revealed a significant (p < .0001) within group effect. VO2 was significantly lower (p < .05) during the 0% arms/WO trial compared to 33% and 42% arms/WO (27.81 ± 2.3 vs. 29.42 ± 2.3 and 30.35 ± 2.1 ml·kg−1·min−1, respectively for 0%, 33% and 42% arms/WO). A higher (p < .05) VE response was elicited when the arms contributed 42% of WO compared to all other exercise trials (37.3 ± 7.2, 39.6 ± 7.5, 39.7 ± 6.5, 39.1 ± 6.5, 41.0 ± 6.6 and 42.8 ± 7.0 L·min−1, respectively for 0%, 8%, 17%, 25%, 33% and 42% arms/WO). HR was significantly higher (p < .05) when the arms contributed 33% and 42% of the WO compared to 0% arms/WO (149 ± 11 vs. 156 ± 13 and 160 ± 11 b·min−1, respectively for 0%, 33% and 42% arms/WO). No significant differences were observed for RER and RPE. These findings suggest that at 60% Wmax cardiovascular responses to combined arm and leg exercise were notably effected when the upper body contributed 33% or more of WO.

Accuracy of prediction equations to estimate submaximal VO2 during cycle ergometry: the HERITAGE Family Study.

It was hypothesized that more accurate equations for estimating submaximal VO2 during cycle ergometry could be developed if more independent variables were used in the equation. The purposes of this study were: (1) to develop new equations for estimating submaximal VO2 during cycle ergometry; and (2) to examine the accuracy of the newly developed equations and those of the American College of Sports Medicine (1995), Berry et al. (1993), Lang et al. (1992), Latin and Berg (1994), and Londeree et al. (1997). Subjects (715 men and women, ages 16-65 yr, from the HERITAGE Family Study) completed a maximal cycle ergometry test, two submaximal trials at 50 W and 60% of VO2max, hydrostatic weighing, and stature and body mass measures before and after 20 wk of cycle ergometry training. Regression analysis generated prediction equations using pretraining data from the 60% trials. No equation with more independent variables was better than an equation that used only power output. This equation, HERITAGE-1, with only power output was cross-validated using the "jackknife" technique. Paired t-tests, mean differences, SEEs, and Es were used to compare the VO2 estimated by HERITAGE-1 and those of previously published equations with the measured VO2 at 60% of VO2max. HERITAGE-1 was slightly better than the equations of ACSM, Lang et al., and Latin and Berg using pretraining data but was not better when using post-training data. All four of these equations were superior to the equations of Berry et al. and Londeree et al.

The Physiological Responses to Walking with and without Power Poles™ on Treadmill Exercise

Power PolesTM are specially constructed, rubber-tipped ski poles designed for use during walking. Using Power PolesTM simulates the arm motion of cross-country skiing, thus increasing the muscle mass used during walking. This study investigated the potential increases in exercise intensity and energy cost associated with the use of walking poles. Thirty-two apparently healthy volunteers (16 men and 16 women) between the ages of 19 and 33 years participated. Each completed a treadmill maximal oxygen consumption (VO2max) test and two randomly assigned, submaximal walking trials (one with poles and one without poles) on separate days. Each walking trial was conducted on a level treadmill, for 20 minutes, at an identical self-selected pace. Expired gases, heart rate in beats per minute (bpm), and ratings of perceived exertion (RPE) were recorded each minute. Results between trials were compared using repeated measures analysis of variance and Tukey's post hoc tests. It was found that walking with poles resulted in an average of 23% (4.4 ml·kg-1·min-1) higher VO2, 22% higher caloric expenditure (1.5 kcal·min-1), and 16% (18 bpm) higher heart rate responses compared to walking without poles on a treadmill. RPE values averaged 1.5 units higher with the use of the poles, and the pattern of responses between conditions was similar for men and women. It is concluded that the use of Power PolesTM can increase the intensity of walking at a given speed and, thus, may provide additional training benefits to walkers.

AEROBIC AND ANAEROBIC CONTRIBUTIONS DURING SIMULATED CANOE/KAYAK SPRINT EVENTS 1256

Twelve members of the USCKT National Sprint team (n=6, male kayakers; n=4, female kayakers; n=2, canoeists) completed submaximal/maximal metabolic tests and simulated 200m, 500m, and 1000m race efforts. All testing was done on a K-1 Ergo (Roger Cargil, Garren, ACT,AUS) paddling ergometer with a power output monitor while open-circuit and heart rate data were collected continuously. The simulated race pieces were 40, 100, and 220 sec for male kayakers and 40, 120, and 240 sec for the others. Based upon the submaximal trials, individual regression equations were developed to predict the oxygen cost from power outputs measured during the simulated events. The aerobic component for these events was obtained from the open-circuit measurements and the anaerobic component by subtracting the aerobic component from the predicted oxygen cost. The means, standard deviations, and ranges for the aerobic contributions as a percent are presented below:Table Within each event, the aerobic contribution increased as the duration increased. Although the mean values were similar across groups, individual values differed by as much as 14% suggesting differences due to training status or genetic predisposition.

INTER-LABORATORY RELIABILITY OF VO2MAX AND SUBMAXIMAL MEASUREMENTS87

Oxygen uptake data is routinely used in exercise prescription. Unfortuately, little is known about inter-laboratory analytical variability in oxygen uptake measurements. Therefore, the purpose of this study was to determine inter-laboratory variability of maximal and submaximal metabolic measurements. Subjects (n=8) performed three submaximal treadmill trials (5 min each at 3 mph and 5.5 mph) and three maximal treadmill tests at 3 separate laboratories using SensorMedics 2900 Metabolic Carts. A standardized maximal incremental protocol was used for all subjects. A minimum time of 48 hours between tests was required and all tests for each subject were performed within 2 weeks. Each subject was scheduled at the same time of day for all 3 tests. The R values from the submaximal running were found to be significantly different between labs(p<.05). Otherwise, no significant differences in metabolic measurements were found with submaximal walking and running(p<.05). The means of the VO2max values are shown in the followingtable: Based on the comparison of the means, most variables were stable between the labs. However, VO2max (ml/kg/min) for lab A was ≅ 1.9 METS greater than labs B and C. In conclusion, although most submaximal and maximal values were stable between labs, caution should be taken in making inter-laboratory comparisons of VO2max measures.

Reliability and Validity of a Portable Metabolic Measurement System

The purpose of this study was to assess the reliability and validity of a portable metabolic system (TEEM 100) during submaximal and maximal (VO2max) exercise using a computer-based metabolic system as the reference system (REF). Between repeated trials of submaximal exercise at three constant loads, differences in ventilation (Ve) and oxygen consumption (VO2) were 0.2 +/- 4.9 L . min-1 and 0.03 +/- 0.10 L . min-1 for REF, and 1.9 +/- 0.7 L . min-1 and 0.00 +/- 0.17 L . min-1 for TEEM 100. Pooled intraclass reliability coefficients for Ve and VO2 calculated from the repeated submaximal trials were r = .89 and r = .94 for REF, and r = .86 and r = .94 for the TEEM 100. Respiratory exchange ratio (RER) measured by the TEEM 100 was significantly higher (p = .01) at only the lowest workload. At VO2max, the TEEM 100 recorded significantly higher values for FeO2 (p = .01) and RER (p < .001). These results suggest that the TEEM 100 provides reliable and valid measurements of VO2 during submaximal and maximal exercise.

Evaluation of the ACSM submaximal ergometer test for estimating &amp;OV0312;O2max

The purpose of this investigation was to assess the reliability and validity of maximal oxygen uptake estimates (ESTmax) from the ACSM submaximal cycle ergometer test. Subjects included 15 men and 15 women aged 21-54 yr who performed two submaximal tests and one maximal cycle ergometer test to determine maximal oxygen uptake (VO2max). During the submaximal tests, heart rates (HR) were recorded from a radio telemetry monitor. ESTmax was predicted for both submaximal trials by extrapolating HR to an age-predicted maximal HR. Correlation coefficient and standard error of measure (SEmeas) for ESTmax between submaximal trials were r = 0.863 and SEmeas = 0.40 l.min-1, while a t-test revealed no significant difference between trials. Although trial means were not significantly different, large variation in individual cases was evident by the high SEmeas (0.40 l.min-1) and by a large SEmeas expressed as a percentage of the mean (13%). The mean of the two ESTmax significantly overestimated measured VO2max with percent error, total error, and mean error equal to 25.7%, 0.89 l.min-1, and 0.63 l.min-1, respectively. The standard error of estimate expressed as a percentage of the mean was equal to 16% and 15% for both ESTmax. In summary, the ACSM protocol failed to be reliable as represented by the large differences found between submaximal trials. Furthermore, the protocol significantly overestimates VO2max and should not be used when an accurate assessment of VO2max is required.

Comparative Exercise Responses of Deep-Water and Treadmill Running

This study compared the physiological, perceptual, and metabolic responses of peak and moderate intensity deep-water running and treadmill running. Eight well-trained male runners performed peak deep-water and treadmill running tests and participated in three 15-min steady-state submaximal exercise trials; (a) treadmill running at 75% of treadmill running 02peak, (b) deep-water running at an estimated 75% (actual approx. 70%) of deep-water running O2,peak, and (c) deep-water running at 75% of treadmill running 02peak. Peak oxygen consumption and heart rate were significantly greater (p < 0.05) for treadmill running. At similar relative and absolute exercise intensities, blood lactate and respiratory exchange ratio were significantly greater during deep-water running. At the same absolute exercise intensity, rating of perceived exertion was also significantly greater during deep-water running. Although at a similar relative exercise intensity treadmill running O2, was significantly greater than deep-water running, no significant differences were found for heart rate between trials. Thus it appears there are differences in exercise responses between peak as well as moderate intensity deep-water and treadmill running.

Maximal inspiratory pressure: does reproducibility indicate full effort?

Maximal inspiratory pressure (MIP) is often relied upon as an index of inspiratory muscle strength, and reproducibility of MIP taken to indicate maximal effort. This study was designed to determine whether reproducibility is a valid indicator of maximal effort. Ten normal subjects were studied, all of whom were familiar with the MIP test but none was an experienced subject. They were told that the purpose was to measure how accurately they could generate 50% of their MIP. Each performed nine MIP efforts and nine submaximal efforts. Means and coefficients of variation of peak negative inspiratory pressure (Pmax) and the ranges of the best three efforts were calculated for each type. Mean (SE) Pmax averaged-93.8 (6.0) cm H2O for the maximal efforts and -60.6 (7.7) cm H2O for the submaximal trials, with coefficients of variation averaging 8.71 (1.75)% and 14.58 (2.63)%, respectively and the ranges averaging 6.5 (1.1)% and 13.4 (3.5)%, respectively. There was no clear separation between the coefficients of variation or ranges of maximal and submaximal efforts. In four cases the ranges of the best three submaximal efforts were less than 5 cm H2O and less than 5% -criteria that have been used to validate MIP results. These four subjects had lower ranges for submaximal than maximal efforts, even when expressed as percentages of the means. Reproducibility should not be relied upon to indicate a valid MIP test, especially for research purposes when relatively small changes in inspiratory muscle strength must be discriminated.

Physiologic and symptomatic responses of cardiac patients to resistance exercise

The purpose of this study was to investigate the symptomatic and physiologic responses during moderate to heavy resistance exercise in a population with coronary artery disease. After at least 12 weeks of aerobic training without experiencing complications, 15 male cardiac patients were selected for the study. Approximately one week after a graded exercise test (GXT), each patient's maximal voluntary contraction (MVC) was determined on seven upper-body Nautilus machines. Resistance exercises, consisting of two sets of seven repetitions at a submaximal intensity (75% MVC) for each exercise, were then performed on two nonconsecutive occasions; symptomatic, hemodynamic, and electrocardiographic responses were recorded and analyzed for patients both on and off beta-blockers. During the MVC and submaximal exercise trials, no significant untoward hemodynamic change was noted with heart rate, systolic blood pressure, diastolic blood pressure, or rate pressure product, and no patient complained of angina or developed ischemic electrocardiographic changes. However, three incidences of premature ventricular contractions (PVCs) occurred. During the GXT, there were 13 incidences of angina, ischemia, or PVCs. Patients taking beta-blockers had significantly lower (p less than .01) values for heart rate and rate pressure product during the GXT, MVC, and submaximal trials. These results suggest that clinically stable, aerobically trained cardiac patients may perform moderate to heavy resistance exercises without experiencing complications.