VO2 Reserve Research Articles

Use of Actigraphs and Self Report to Measure Bouts and Intensity of Exercise in Cancer Survivors

PURPOSE: Exercise intensity is measured using various techniques including heart rate, VO2 reserve, and perceived exertion (RPE). Actigraphs have been used to assess light, moderate, and hard intensity exercise and confirm self report physical activity. The purpose of this pilot study was to determine if the amount of self reported bouts and intensities of exercise matched Actigraph reports. METHODS: Twenty endometrial cancer survivors (Age=58.5y, BMI=31kg/m2 VO2= 18. 8ml/kg/min) were given a short term personalized exercise prescription after completing a graded sub-maximal cycle ergometer exercise test. Participants were asked to report all exercise sessions and intensities (RPE) in diaries for one week. Participants were also asked to wear an Actigraph during the same week. RESUITS: Nineteen survivors returned usable diary data and the Actigraphs for data analysis. Ninety-five percent of the survivors reported performing the amount of exercise prescribed in the first week. The self reported time of exercise matched the time and duration of exercise recorded on the Actigraph for 84% of the reported bouts of exercise. Self-reported intensity of exercise matched the Actigraph for 70% of the reported bouts of exercise. Of the 30% that was incorrectly reported, exercise intensity was over reported 42% and under reported 58%. CONCLUSIONS: The data suggests this sample of cancer survivors generally reported time and duration of exercise correctly. Intensity of exercise was less accurately reported. Previously sedentary participants in exercise studies may need additional instruction to identify appropriate exercise intensities before beginning exercise programs. Funding Source: NIHgrantsR01 CA1099919, R25 CA57730, P30 CA016672

Unreliability of the %VO2 reserve versus %heart rate reserve relationship for aerobic effort relative intensity assessment in chronic heart failure patients on or off beta-blocking therapy

Percentage of heart rate reserve (%HRR) has been shown to be equivalent to percentage of VO2 reserve (%VO2R) in normal individuals, but it is not clear whether this is also true for chronic heart failure (CHF) patients. This study aimed to evaluate the reliability of the %VO2R versus %HRR relationship for aerobic effort relative intensity assessment in CHF patients. We studied 388 patients with CHF, of whom 213 were on carvedilol (CHF on betab) and 175 were off the drug (CHF off betab), and 40 normal individuals (N). %VO2R and %HRR values were evaluated at matched steps during cardiopulmonary exercise testing. The %VO2R versus %HRR regression was determined for each group (CHF, CHF on betab, CHF off betab, N) as a whole and as the mean of individual regressions. %VO2R strongly correlated with %HRR in both N and CHF, at both group and mean individual regressions, with slope and y-intercept values significantly lower and higher, respectively, in CHF than N. The 95% prediction interval of %VO2R for a given %HRR value was 24% points in N but rose to 41 in CHF, and the mean regression line coincided with identity line in N but not in CHF. These results were independent of beta-blockade. In CHF patients the %VO2R versus %HRR relationship is unreliable for assessment of aerobic effort relative intensity, because of a large prediction interval of %VO2R and lack of coincidence with the identity line, independently of beta-blocking therapy. This implies that the %VO2R versus %HRR relationship should be determined directly in each patient.

Exercise Target Heart Rate Prescription in Obese Individuals

PURPOSE: The purpose of the present study was to assess the equivalency between the VO2 reserve (VO2R), heart rate reserve (HRR), and maximal heart rate (HRmax) methods to prescribe an exercise target heart rate (HR) following a maximal graded exercise test in obese individuals. METHODS: Sixty-eight overweight to severely obese and sedentary adults (mean ± standard deviation) (BMI=34.9±4.6 kg·m−2, resting HR=84±11 bpm, resting VO2=2.5±0.5 ml·kg−1, HRmax=178±11 bpm, VO2peak=25.1±4.3 ml·kg−1·min−1) performed a Bruce ramp protocol on a treadmill. Resting heart rate was determined after 15 min of rest in a sitting position prior the stress test and was used for HRR calculation. Resting metabolism was measured on a separate occasion in a recumbent position and was used for VO2R calculation. Exercise target HR was defined at 6 relative intensities (I-) where I-1=40%/64%, I-2=50%/71%, I-3=60%/77%, I-4=70%/84%, I-5=80%/91%, and I-6=85%/94% of VO2R or HRR / HRmax respectively, according to ACSM's guidelines. Six one way repeated measure ANOVAs were done to compare target HR between the 3 proposed methods for each intensity. Three one way repeated measure ANOVAs (6 intensities) were performed to compare delta target HR between HRR-VO2R, HRmax-VO2R, and HRmax-HRR. RESULTS: Target HR calculated by HRR was 6±7, 7±8, 7±8, 6±8, 5±7, and 4±6 bpm significantly higher (p<0.001) than VO2R from I-1 to I-6 respectively. Target HR calculated by HRmax was not significantly different than VO2R at I-1 (−2±9) and I-2 (1±10) but was significantly higher (p<0.01) from I-3 to I-6 and was equal to 3±9, 5±8, 8±7, and 7±7 bpm respectively. Target HR calculated by HRmax was−9±6,−6±5, and−4±4 bpm significantly lower (p<0.001) than HRR from I-1 to I-3, not significantly different at I-4 (−1±3), and significantly higher (p<0.001) at I-5 (2±2) and I-6 (3±2). No intensity effect for delta target HR between HRR and VO2R was found. Delta target HR between HRmax and VO2R were significantly different (p<0.001) from each other from I-1 to I-5 but not between I-5 and I-6. Delta target HR between HRmax and HRR were significantly different from each other between intensities (p<0.001). CONCLUSIONS: The slightly but significant (6±7 bpm) difference between target HR calculated by HRR and VO2R is constant among intensities. However, the difference between target HR calculated by HRmax and VO2R or HRmax and HRR both fluctuate between relative intensities. These results have their importance for exercise target HR prescription in obese individuals.

The individual relationship between heart rate and oxygen uptake in people with a tetraplegia during exercise

Descriptive study. To examine the individual heart rate-oxygen uptake (HR-VO(2)) relationship during exercise in persons with tetraplegia (TP). Rehabilitation Centre Heliomare, Wijk aan Zee, The Netherlands. The HR-VO(2) relationship was determined in untrained subjects with motor complete TP (C5 or C6, n=10 and C7 or C8, n=10) during a discontinuous graded exercise hand cycle test. The mean HR and VO(2) of the final 60 s of 2-min exercise blocks were used for calculation of the individual correlation coefficient and the standard error of the estimate (SEE). Two subjects of the C5-C6 group were not able to complete the test. Individual Pearson's correlation coefficients (r) ranged from 0.68 to 0.97 and SEE from 2.6 to 22.4% VO(2)-Reserve (VO(2)R). The mean Pearson's r and SEE were 0.81+/-0.12 and 10.6+/-5.6% VO(2)R in the C5-C6 group and 0.91+/-0.07 and 7.0+/-3.2% VO(2)R in the C7-C8 group, respectively. Two subjects of the C5-C6 group and six subjects of the C7-C8 group attained a linear HR-VO(2) relationship with an acceptable SEE (< or =6.0%) and r (>0.90). The HR-VO(2) relationship appeared linear in only eight out of 18 subjects. An individual analysis of the HR-VO(2) relationship is necessary to determine whether HR can be used to quantify exercise intensity. The use of HR to prescribe training intensity should be reconsidered in persons with TP. This study is supported from a grant by ZON-MW.

Oxygen Uptake and Heart Rate Kinetics during Moderate and Heavy Work-to-Work Transitions

The time course of phase II oxygen uptake (VO2) is slower during step transitions from an elevated exercising baseline (∼45% ventilatory threshold, VT) compared with resting or very low-level intensity baselines. The slowing in VO2 during the on-transient from an elevated exercising baseline at ∼45% VT is likely due to an attenuated heart rate (HR) response. However, the time course of VO and HR during work-to-work transitions in the moderate (between 45 and 100% VT) and heavy (above VT) exercise intensity domain is unknown. PURPOSE: The purpose of this study was to investigate VO2 and HR on-transient responses from elevated exercising baselines at moderate and heavy exercise intensities. We hypothesized 1) that the time course of phase II VO2 would not differ during work-to-work transitions from moderate and heavy intensity exercising baselines, 2) that a shift in the relative contribution of phase II and phase III responses would be observed during progressively heavier exercise, and 3) that the overall time course (mean response time, MRT) of VO2 would be directly related to the MRT of HR. METHODS: Following determination of VT and peak VO2, 13 trained male cyclists (mean± SD; age 25 ± 3.7 years; height 1.82 ± 0.07 m; weight 78.9 ± 8.0 kg; peak VO2 4.48 ± 0.46 L/min) completed work-to-work transitions representing moderate (40–50 and 50–60% VO2 reserve) and heavy (70–80 and 80–90% VO2reserve) exercise intensities. The time course and amplitude response of VO and HR was determined using a first or second-order non-linear exponential model. Comparisons were made with ANOVA and p <0.05 was considered significant. RESULTS: The time course of phase II VO2 during work-to-work transitions from 40–50(21 ± 10 s), 50–60 (22 ± 16 s), 70–80 (19 ± 4 s), and 80–90% VO2 reserve (20 ± 10 s) were not significantly different (p >0.05). As well, the time course of phase II HR during work-to-work transitions from 40–50 (23 ± 12 s), 50–60 (22 ± 12 s), 70–80 (21 ± 15 s), and 80–90% VO2 reserve (26 ± 21 s) were not significantly different (p >0.05). There was a non-significant trend (F = 2.45, p = 0.079) for a reduction in the phase II VO amplitude response during heavy work-to-work transitions, with a similar significant effect observed in HR. The MRT of HR was significantly correlated with VO2 where MRT VO2 = 0.61 (MRT HR) + 29.3 (r = 0.73, p <0.001) CONCLUSION: VO and HR respond in a linear fashion during work-to-work transitions from moderate and heavy intensity exercising baselines. The significant relationship between the MRT of HR and VO2 suggests that the time course of VO2 is HR and thus, O2 delivery dependent.

Relationship Between Percent Heart Rate Reserve and Percent MET Reserve in Patients with Heart Disease on Beta Blockade Therapy

In the absence of appropriate heart rate (HR) data to prescribe exercise due to a change in beta blocker therapy, an acceptable alternative is to utilize MET levels. It has been reported that percent Heart Rate Reserve (HRR) closely approximates the same percentage for both the % VO2 reserve and % MET reserve in individuals with and without heart disease during an exercise test. However, the relationship of % MET reserve to % HRR during actual exercise training in patients taking a beta-adrenergic blocking agent is unknown. PURPOSE: To test the hypotheses that % MET reserve and % HRR during exercise training are significantly and meaningfully related in patients with heart disease on beta blockade. METHODS: A retrospective assessment of patients (n=39; 92% male, 46% Caucasian, age 53± 5 years) who participated in cardiac rehabilitation (CR) was completed by conducting a manual chart review. Included in the study were men and women age 40–60 yr with a history of heart disease and on beta blockade therapy. Peak MET and HR were measured during a symptom limited maximal stress test. Percent MET reserve was calculated based on the exercise training work rates measured in CR within two weeks of the stress test which was performed at a similar time of day as their exercise in CR. Linear regression was used to evaluate the relationship between % MET and % HRR reserve. RESULTS: Mean peak MET and peak HR were 6.2± 1.3 and 128± 21beats/min, respectively. The correlation between % MET reserve and % HRR reserve was calculated at r=0.66 (p<0.01). The standard error of the estimate (SEE) was 14% (e.g., a workload set at 60% MET reserve would result in a HRR of 46–74%). CONCLUSION: Contrary to our hypothesis, % MET reserve and % HRR during exercise training, although significantly related, may not be clinically meaningful based on the large SEE. This supports the importance of also using rating of perceived exertion when guiding exercise intensity. A prospective trial is needed to better define the MET reserve/HRR relationship and identify sources of variability, before it is used as a method to prescribe exercise in patients with heart disease on beta blockade therapy.

Effectiveness of an Upper Extremity Exercise Device Integrated With Computer Gaming for Aerobic Training in Adolescents With Spinal Cord Dysfunction

Background/Objective: To determine whether a new upper extremity exercise device integrated with a video game (GameCycle) requires sufficient metabolic demand and effort to induce an aerobic training effect and to explore the feasibility of using this system as an exercise modality in an exercise intervention.Design: Pre-post intervention.Setting: University-based research facility.Subject Population: A referred sample of 8 adolescent subjects with spina bifida (4 girls, 15.5 ± 0.6 years; 4 boys, 1 7.5 ± 0.9 years) was recruited to participate in the project. All subjects had some level of mobility impairment that did not allow them to participate in mainstream sports available to their nondisabled peers. Five subjects used a wheelchair full time, one used a wheelchair occasionally, but walked with forearm crutches, and 2 were fully ambulatory, but had impaired gait.Main Outcome Measures: Peak oxygen uptake, maximum work output, aerobic endurance, peak heart rate, rating of perceived exertion, and user satisfaction.Results: Six of the 8 subjects were able to reach a Vo2 of at least 50% of their Vo2 reserve while using the GameCycle. Seven of the 8 subjects reached a heart rate of at least 50% of their heart rate reserve. One subject did not reach either 50% of Vo2 reserve or 50% of heart rate reserve. Seven of the 8 subjects increased their maximum work capability after training with the GameCycle at least 3 times per week for 16 weeks.Conclusions: The data suggest that the GameCycle seems to be adequate as an exercise device to improve oxygen uptake and maximum work capability in adolescents with lower extremity disability caused by spinal cord dysfunction. The subjects in this study reported that the video game component was enjoyable and provided a motivation to exercise.

Exercise and hypertension: Recent advances in exercise prescription

Despite the pervasiveness of hypertension (HTN), the exercise dose needed to lower blood pressure (BP) remains to be quantified. The purpose of this manuscript is to discuss recent advances in exercise prescription (ExR x) for HTN. The take-home message in ExR x for those with HTN is that the antihypertensive effect is: immediate; elicited by low intensity, short-duration aerobic exercise; one of many health benefits; and individually tailored. With this message and the general rules of ExR x as a guide, those with HTN should exercise on most, preferably all, days of the week, with moderate intensity (40% to <60% of VO2 Reserve), for 30 minutes or more of continuous or accumulated physical activity per day, primarily of the endurance type, supplemented by resistance exercise. Additionally, those who are overweight should progress to a caloric energy expenditure of a minimum of 1000 kcal to more than 2000 kcal per week or more than 2.5 hours per week of moderate-intensity, aerobic exercise.

Complete recovery time after exhaustion in high-intensity work

This study was aimed to investigate complete recovery time (CRT) after exhaustion in high-intensity work. Twenty-four subjects were divided into two groups based on the cardiorespiratory capability index, which was measured in a maximum capacity test. Each subject then performed two cycling tests (at 60% and 70% maximum working capacity). The subject continued cycling until exhaustion in each test and then sat recovering until he/she no longer felt fatigue or until the oxygen uptake (VO2) and heart rate (HR) returned to their baselines, whichever was longer. The results indicated that HR required the longest time to recover and, consequently, HR data were adopted to set the CRT. The CRT was significantly correlated with the cardiorespiratory capability index and the relative workload indices: RVO2 and RHR. The RVO2 was the average elevation in VO2 during work from the resting level as a percentage of maximum VO2 reserve. The RHR's definition was similar to that of RVO2. Based on the obtained CRT-prediction model, the CRT for a high-cardiorespiratory-capability person was 20.8, 22.1, 23.4, and 24.7 min at 50%, 60%, 70%, and 80% RHR levels, respectively. These suggested CRT values should be increased by 10 min for a low-cardiorespiratory-capability person.

Heart Rate Variability after Isocaloric Exercise Bouts of Different Intensities

To examine cardiac autonomic modulation, via heart rate variability (HRV), after exercise bouts at 50% (LO) and 80% (HI) of VO2 reserve (VO2R). Thirteen male volunteers (age: 25.7+/-3 yr) exercised on a treadmill at either LO or HI (randomly assigned) on separate days, expending 300 kcal during each bout. During each visit, electrocardiogram (ECG) recordings were obtained during a supine 5-min period before exercise (PRE) and during 30 min of postexercise supine recovery (POST). The last 25 min of POST was divided into five 5-min segments to closely examine postexercise HRV. ECG segments were analyzed for the standard deviation of RR intervals (SDNN), whereas total- (lnTP), low- (lnLF), and high-frequency (lnHF) power were obtained via spectral analysis. LF and HF were further normalized (LFNU and HFNU) to better quantify autonomic balance. There were main effects of time and intensity on SDNN such that it was lower than PRE until 15 min POST, and lower after HI. There were significant intensity x time interactions on lnTP, lnLF, lnHF, LFNU, HFNU, and lnLF/lnHF. Post hoc analysis revealed that lnTP and lnLF were lower than PRE up to 20 min POST after HI. lnHF was lower than PRE for 25 min POST for HI, and for 10 min POST for LO. LFNU and lnLF/lnHF were greater, whereas HFNU was lower, compared with PRE up to 15 min POST, and from 20-25 min POST for HI only. Exercise at 50% VO2R caused less of a shift in the cardiac autonomic balance, with a quicker restoration of vagal modulation than exercise at 80% VO2R.

Moderate or Vigorous Intensity Exercise: Which Is Better for Improving Aerobic Fitness?

Moderate or Vigorous Intensity Exercise: Which Is Better for Improving Aerobic Fitness?

Validation of a new method for estimating VO2max based on VO2 reserve.

The American College of Sports Medicine's (ACSM) preferred method for estimating maximal oxygen consumption (VO2max) has been shown to overestimate VO2max, possibly due to the short length of the cycle ergometry stages. This study validates a new method that uses a final 6-min stage and that estimates VO2max from the relationship between heart rate reserve (HRR) and VO2 reserve. A cycle ergometry protocol was designed to elicit 65-75% HRR in the fifth and sixth minutes of the final stage. Maximal workload was estimated by dividing the workload of the final stage by %HRR. VO2max was then estimated using the ACSM metabolic equation for cycling. After the 6-min stage was completed, an incremental test to maximal effort was used to measure actual VO2max. Forty-nine subjects completed a pilot study using one protocol to reach the 6-min stage, and 50 additional subjects completed a modified protocol. The pilot study obtained a valid estimate of VO2max (r = 0.91, SEE = 3.4 mL x min(-1) x kg-1) with no over- or underestimation (mean estimated VO2max = 35.3 mL x min(-1) x kg(-1), mean measured VO2max = 36.1 mL x min(-1) x kg(-1)), but the average %HRR achieved in the 6-min stage was 78%, with several subjects attaining heart rates considered too high for submaximal fitness testing. The second study also obtained a valid estimate of VO2max (r = 0.89, SEE = 4.0 mL x min(-1) x kg(-1)) with no over- or underestimation (mean estimated VO2max = 36.7 mL x min(-1) x kg(-1), mean measured VO2max = 36.9 mL x min(-1) x kg(-1), and the average %HRR achieved in the 6-min stage was 64%. A new method for estimating VO2max from submaximal cycling based on VO2 reserve has been found to be valid and more accurate than previous methods.

Evaluation of ACSM Guidelines on Prescribing Exercise Intensity for “Quite Unfit”

0062 In 1998, the ACSM revised its guidelines for prescribing the intensity of aerobic exercise, adding that one could lower the intensity to 40% VO2 reserve (VO2R) for “quite Unfit” people. PURPOSE: To investigate the relationship between %VO2R and the ventilatory threshold (vt) in 442 initially sedentary individuals (ages 17 to 65). METHODS: Each participant completed 2 graded cycle tests to exhaustion before and after 20 weeks of training. VO2 and heart rate data were collected at the end of each stage. The absolute (ml•kg−1•min−1) and relative (%VO2R) values for VO2vt were determined for each subject. RESULTS: The average absolute values for VO2vt were about 10–14 ml•kg−1•min−1 for 183 subjects whose VO2 max was 15.4–29.9 ml•kg−1•min−1. This is similar to the value of 15 ml•kg−1•min−1 that Shephard states is associated with activities of daily living. The range of relative values for the VO2vt of these subjects was 42–83% VO2R, with most subjects between 50% and 70% VO2R. Intensities below VO2vt are generally aerobic in nature and can be done without much distress. It should be noted that these subjects began the training program by exercising for 30 minutes at the heart rate associated with 50% VO2 max and had few problems. CONCLUSION: Because “quite Unfit” sedentary subjects are already doing enough activity in their daily lives to maintain a VO2vt at levels that are generally greater than 50% VO2R, it is not necessary to reduce the prescribed intensity to 40% VO2R, as recommended by the ACSM. Supported by multiple grants from NIH-NHLBI.

Evaluation of ACSM Guidelines on Prescribing Exercise Intensity for ???Quite Unfit???

0062 In 1998, the ACSM revised its guidelines for prescribing the intensity of aerobic exercise, adding that one could lower the intensity to 40% VO2 reserve (VO2R) for “quite Unfit” people. PURPOSE: To investigate the relationship between %VO2R and the ventilatory threshold (vt) in 442 initially sedentary individuals (ages 17 to 65). METHODS: Each participant completed 2 graded cycle tests to exhaustion before and after 20 weeks of training. VO2 and heart rate data were collected at the end of each stage. The absolute (ml•kg−1•min−1) and relative (%VO2R) values for VO2vt were determined for each subject. RESULTS: The average absolute values for VO2vt were about 10–14 ml•kg−1•min−1 for 183 subjects whose VO2 max was 15.4–29.9 ml•kg−1•min−1. This is similar to the value of 15 ml•kg−1•min−1 that Shephard states is associated with activities of daily living. The range of relative values for the VO2vt of these subjects was 42–83% VO2R, with most subjects between 50% and 70% VO2R. Intensities below VO2vt are generally aerobic in nature and can be done without much distress. It should be noted that these subjects began the training program by exercising for 30 minutes at the heart rate associated with 50% VO2 max and had few problems. CONCLUSION: Because “quite Unfit” sedentary subjects are already doing enough activity in their daily lives to maintain a VO2vt at levels that are generally greater than 50% VO2R, it is not necessary to reduce the prescribed intensity to 40% VO2R, as recommended by the ACSM. Supported by multiple grants from NIH-NHLBI.

%Heart Rate Reserve Is Better Related to %VO2max Than to %VO2 reserve

0063 The intensity guidelines for prescribing aerobic exercise were recently revised by ACSM to use %VO2reserve (%VO2R) rather than %VO2max. PURPOSE: The current study investigated the relationship of %VO2max and %VO2R with %Heart Rate Reserve (%HRR) in 630 initially sedentary individuals (ages 17 to 65). METHODS: Each participant completed 2 graded cycle tests to exhaustion before and after 20 weeks of training. VO2 and HR data were collected at the end of each stage. Resting HR and estimated resting VO2 (3.5 ml•kg−1•min−1) were additionally used to determine linear regressions of %HRR vs. %VO2max and %HRR vs. %VO2R. Slope and intercept were determined pre- and post-training for the total cohort and for subjects grouped by gender, race, age and baseline fitness (VO2max). RESULTS: Overall, and in all sub-groups, both pre- and post-training, the slope and intercepts were significantly different from 1.0 and 0, respectively for both %HRR vs. %VO2max and %HRR vs. %VO2R. However, the slopes and intercepts for %HRR vs. %VO2max were closer to the line of unity than were the slopes and intercepts of %HRR vs. %VO2R (p< 0.01 to 0.0001). More importantly, the calculated HR values for %HRR vs. %VO2max were closer (p<0.001) at 50% (+0.4±2.2 bpm) and 85% (+3.8 ± 3.2) than the values for %HRR vs. % VO2R at 50% (+8.2 ± 2.6 bpm) and 85% (+6.6 ± 3.4 bpm). Posttraining data differences were similar, though of smaller magnitude, with HR values at 50 and 85% VO2max more similar (p<0.01) to %HRR than were %VO2R HR values to %HRR. CONCLUSION: These results differ from those of Swain et al. who studied young adults during treadmill (n = 50) and cycle (n = 57) testing. Since %VO2R is a more difficult calculation than %VO2max and is less understood and since the differences in HR values within the normal aerobic training range were significantly closer using %VO2max, %VO2max is the better measure for prescribing exercise intensity. Supported by multiple grants from NIH/NHLBI.

%Heart Rate Reserve Is Better Related to %VO2max Than to %VO2 reserve

0063 The intensity guidelines for prescribing aerobic exercise were recently revised by ACSM to use %VO2reserve (%VO2R) rather than %VO2max. PURPOSE: The current study investigated the relationship of %VO2max and %VO2R with %Heart Rate Reserve (%HRR) in 630 initially sedentary individuals (ages 17 to 65). METHODS: Each participant completed 2 graded cycle tests to exhaustion before and after 20 weeks of training. VO2 and HR data were collected at the end of each stage. Resting HR and estimated resting VO2 (3.5 ml•kg−1•min−1) were additionally used to determine linear regressions of %HRR vs. %VO2max and %HRR vs. %VO2R. Slope and intercept were determined pre- and post-training for the total cohort and for subjects grouped by gender, race, age and baseline fitness (VO2max). RESULTS: Overall, and in all sub-groups, both pre- and post-training, the slope and intercepts were significantly different from 1.0 and 0, respectively for both %HRR vs. %VO2max and %HRR vs. %VO2R. However, the slopes and intercepts for %HRR vs. %VO2max were closer to the line of unity than were the slopes and intercepts of %HRR vs. %VO2R (p< 0.01 to 0.0001). More importantly, the calculated HR values for %HRR vs. %VO2max were closer (p<0.001) at 50% (+0.4±2.2 bpm) and 85% (+3.8 ± 3.2) than the values for %HRR vs. % VO2R at 50% (+8.2 ± 2.6 bpm) and 85% (+6.6 ± 3.4 bpm). Posttraining data differences were similar, though of smaller magnitude, with HR values at 50 and 85% VO2max more similar (p<0.01) to %HRR than were %VO2R HR values to %HRR. CONCLUSION: These results differ from those of Swain et al. who studied young adults during treadmill (n = 50) and cycle (n = 57) testing. Since %VO2R is a more difficult calculation than %VO2max and is less understood and since the differences in HR values within the normal aerobic training range were significantly closer using %VO2max, %VO2max is the better measure for prescribing exercise intensity. Supported by multiple grants from NIH/NHLBI.

Validity Of A New Method For Estimating VO2max – Part II

0606 It has been found that the current ACSM cycle ergometer protocol overestimates VO2max by 28% on average (Swain and Wright, 1997). A new method based on the one-to-one relationship between heart rate reserve (HRR) and VO2 reserve, and using a final cycle ergometer stage of 6 minutes, eliminated the overestimation, but the protocol resulted in excessively high heart rates. PURPOSE: To design and test the validity of a new cycle ergometer protocol for estimating VO2max with the VO2 reserve method, with a test-termination heart rate of 75% HRR. METHODS: There were 50 subjects (25 male, 25 female) who were between 18 and 44 years old and met the definition of ‘low risk’ by ACSM guidelines. Following measurement of resting heart rate, the subjects performed a submaximal cycle ergometer test at a cadence of 60 rpm. The initial resistance was ¼ kg for subjects < 90 kg and ½ kg for those > 90 kg. Resistance was increased each minute until 45% HRR (for inactive subjects) or 55% HRR (for active subjects) was reached, and a final 6 minute stage commenced targeting no more than 75% HRR The workload of the 6-min stage was divided by the %HRR attained to estimate maximal workload, and VO2max was estimated using the ACSM metabolic equation for cycling. For comparison, VO2max was also estimated using the Astrand nomogram. At the conclusion of the submaximal test, an incremental test was performed to determine actual VO2max. RESULTS: The average HR during the 6-min stage was 65% HRR. The new method did not overestimate or underestimate VO2max (estimated VO2max = 36.7 ± 8.4 ml.min−1.kg−1, actual VO2max = 36.9 ± 8.8 ml.min−1.kg−1). Further, a regression performed on actual VO2max vs. the estimated VO2max from the VO2 reserve method yielded an r of 0.89 and an SEE of 4.0 ml.min−1.kg−1. The Astrand estimate of VO2max yielded an r of 0.82 and an SEE of 5.1 ml.min−1.kg−1, and overestimated VO2max by 8% on average. CONCLUSION: The new cycle ergometer protocol did not overestimate VO2max, and attained a higher r and lower SEE when compared to the Astrand method, and when compared to previous research on the current ACSM cycle ergometer protocol. Further research on older, moderate risk populations is warranted.

Post-Exercise Cardiac Autonomic Modulation Following Two Different Exercise Intensities

0432 PURPOSE: To examine cardiac autonomic modulation, via heart rate variability, following exercise bouts at 50% (LO) and 80% (HI) of VO2Reserve (VO2R). METHODS: Thirteen male volunteers (age: 25.7 ± 3 yr) performed a graded treadmill test to obtain VO2peak. During two subsequent visits they exercised on a treadmill at either LO or HI (random1y assigned), with a total energy expenditure of 300 Kcal during each visit. During visits 2 and 3, ECG recordings were obtained during a supine 5-minute period before exercise (PRE) and 30 minutes of post-exercise supine recovery (POST). POST was divided into six 5-minute segments in order to examine postexercise autonomic kinetics, with the first POST segment being excluded from analysis due to an unstable heart rate. Each ECG segment was analyzed for the mean and standard deviation (SDNN) of the RR intervals, and spectral indices [total-(TP), low-(LF), and high-frequency (HF) power] were obtained via fast Fourier transformation. LF and HF were further normalized (LFnu and HFnu) to better quantify autonomic balance. Data that were not normally distributed were transformed using the natural log function. A 2 × 6 ANOVA was used to examine the effects of Time and Intensity and a significance level of 0.05 was used for all tests. RESULTS: Mean RR interval was significantly reduced compared to PRE for both intensities, with a greater drop for HI, and remained depressed at the end of 30 minutes. Main effects of Time and Intensity for SDNN showed that it was lower than PRE until 15 minutes POST. There were significant Intensity × Time interactions for TP, LF, HF, LFnu, HFnu and LF/HF. Posthoc analysis revealed that TP and LF were lower than PRE up to 20 minutes POST with HI only. HF was lower than PRE up to 25 minutes POST for HI and 10 minutes POST for LO. LFnu and LF/HF were greater, whereas HFnu was lower, compared to PRE up to 15 minutes POST for HI only. CONCLUSIONS: Though a recovery period of 30 minutes was sufficient to attain baseline vagal modulation, exercise bouts at 50% of VO2R caused less of a cardiac autonomic imbalance with a quicker restoration of vagal modulation compared to those performed at 80% of VO2R.

PRESCRIBING EXERCISE INTENSITY FOR MASTER ATHLETES

Prescription of exercise intensity is generally based upon relations between VO2, Heart Rate (HR), and HR reserve (HRR) expressed as a percent of maximum. Recent evidence suggests that these relations may be altered by aging. However, it remains unclear how chronic exercise may influence the effect of aging on the relations between %VO2, %HR and %HRR. PURPOSE To determine in Master Athlete's (MA) the efficacy of using the ACSM guidelines as an appropriate method of prescribing exercise intensity. METHODS A total of 157 (mean age 52.3±8 yrs, range 40–77 yrs.) subjects participated in the study (96 males, 61 females). Subjects were considered MA's as evident by their meeting our criteria of 1) Running for a period of > 5 years, 2) Running ≥ 10 mile/week, 3) Older than 40 years of age. Subjects performed a maximal VO2 treadmill examination. Heart rates were assessed during testing by a 12-lead ECG. VO2, and HR were measured at one-minute intervals during the VO2max test and HRR were calculated. One-Sample T-Test's were performed to compare the values obtained to the standards created by ACSM. RESULTS See table (* significantly greater from corresponding ACSM values p < .001)Table: No Caption AvailableCONCLUSION % HRR in MA's is similar to ACSM guidelines however, at increased intensities %HRR is greater than the reported guidelines. % HRmax was not an accurate measure of exercise intensity at any given level of VO2. Modified guidelines for Master athletes need to be established in order to accurately prescribe exercise intensities during exercise.

Clinical evaluation of peak endocardial acceleration as a sensor for rate responsive pacing.

An innovative control parameter for rate responsive (RR) pacing that uses a sensor to measure mechanical vibrations generated by the myocardium during the isovolumetric contraction phase (peak endocardial acceleration [PEA]), has been devised by SORIN Biomedica (BEST Living System). To assess the physiological sensitivity of the pacemaker sensor along with reliability of the algorithm to supply appropriate pacing rates three different relationships were examined (linear regression analysis): (1) recorded deltaPEA exercise steps against the calculated energy cost of exercise (MET), (2) exercise pacing rates against predicted values, and (3) deltaPEA against exercise pacing rates. Fifteen patients (mean age 68 +/- 12 years) in NYHA Class I-II, implanted with the BEST Living System (Living 1 DDDR pacemaker) for advanced AVB and/or SSS, underwent one of the following maximal exercise stress protocols: bicycle (25 W, 2-minute steps) or Bruce or Chronotropic Assessment Exercise Protocol (CAEP). Pacing rates for each step were matched against those predicted by a reliable and tested custom software called Pacing Rate Profile Software (PRPS). The PRPS is based on the oxygen pulse reserve (OPR) method (OPR = VO2 reserve divided by heart rate reserve), American College of Sports Medicine (ACSM) formulas for calculating workload/metabolic requirements, and data derived from the Weber functional classes. On the basis of certain patient, data the PRPS then supplies appropriate metabolic pacing rate profiles. In all 15 patients linear regression analysis of deltaPEA against MET, as evaluated during the exercise protocol steps, showed a high correlation (r = 0.97). Likewise, a high correlation was also obtained between PRPS predicted heart rates and exercise pacing rates (r = 0.96) and PEA against exercise pacing rates (r = 0.96). The results of this study show that, through PEA dynamic monitoring, the SORIN Best Living System produces physiological pacing rates that are significantly related to metabolic needs.