A Machine Learning Approach to the Interpretation of Cardiopulmonary Exercise Tests: Development and Validation.

OBJECTIVE: At present, there is no consensus on the best strategy for interpreting the cardiopulmonary exercise test's (CPET) results. This study is aimed at assessing the potential of using computer-aided algorithms to evaluate CPET data for identifying chronic heart failure (CHF) and chronic obstructive pulmonary disease (COPD). METHODS: Data from 234 CPET files from the Pulmonary Institute, at Sheba Medical Center, and the Givat-Washington College, both in Israel, were selected for this study. The selected CPET files included patients with confirmed primary CHF (n = 73), COPD (n = 75), and healthy subjects (n = 86). Of the 234 CPETs, 150 (50 in each group) tests were used for the support vector machine (SVM) learning stage, and the remaining 84 tests were used for the model validation. The performance of the SVM interpretive module was assessed by comparing its interpretation output with the conventional clinical diagnosis using distribution analysis. RESULTS: The disease classification results show that the overall predictive power of the proposed interpretive model ranged from 96% to 100%, indicating very high predictive power. Furthermore, the sensitivity, specificity, and overall precision of the proposed interpretive module were 99%, 99%, and 99%, respectively. CONCLUSIONS: The proposed new computer-aided CPET interpretive module was found to be highly sensitive and specific in classifying patients with CHF or COPD, or healthy. Comparable modules may well be applied to additional and larger populations (pathologies and exercise limitations), thereby making this tool powerful and clinically applicable.

Counter-Terror Fighting Task: Metabolic Demand and Energy Systems' Contributions.

INTRODUCTION: In light of the recent increase in terrorist events around the globe, it is surprising that the metabolic demand of counter-terror fighting tasks had not yet been published in the scientific literature. The purpose of this study, therefore, was to examine the metabolic demand and the contribution of the three energy systems to a typical simulated counter-terror combat scenario. MATERIALS AND METHODS: Oxygen uptake and carbon dioxide output (VO2, VCO2), heart rate, ventilatory responses, and blood lactate concentration were measured in 12 randomly selected elite Special Forces police fighters (mean age 33.3 ± 3.6 years). The fighting task involved ascending flights of stairs, climbing a ladder, shooting on hiding terrorists, performing a search and rescue, relocating a wounded colleague, and then descending and exiting from a seven-floor building. RESULTS: The fighting scenario lasted an average of 4:56 ± 0:22 min. Measured oxygen uptake averaged 31.1 ± 2.0 ml kg min-1 (57.7% of VO2max) with an average peak of 37.7 ± 8.1 ml kg min-1 (75.5% of VO2max). Average and peak heart rates were 160.4 ± 12.2 beats min-1 (85% of the HRmax) and 175.5 ± 10.5 beats min-1 (94% of HRmax), respectively. The energy cost of the fighting scenario averaged 74.3 ± 9.9 Kcal, with 75.5% of the energy generated by aerobic pathways, 14.1% from anaerobic lactacid (glycolytic) and 10.4% from anaerobic a-lactacid (phosphogenic) energy sources. CONCLUSIONS: This study provided novel information related to the physiological demands and the metabolic fuel supplies during a typical counter-terror-fighting task of elite Special Forces. Such information is instrumental in planning and conducting adequate training programs and nutrition support for counter-terror fighting units.

[PRINCIPLES FOR THE INTERPRETATION OF CARDIOPULMONARY EXERCISE TESTS (CPET)].

INTRODUCTION: The cardiopulmonary exercise test (CPET) permits the most accurate and reproducible quantification of cardiopulmonary fitness, a grading of the etiology and severity of cardiopulmonary impairments, and an objective assessment of the response to an intervention. Moreover, over the last three decades, a large volume of research has been directed toward the utility of CPET as a diagnostic and prognostic tool; these studies have established CPET as a scientifically sound and, therefore, clinically valuable method for accurately assessing exercise limitation and prognosis in various disease states. The CPET is relatively easy to perform, yet complex in the interpretation of the results. The current review presents the principles of the analytic process of the test results, in order to obtain possible diagnoses.

Recovery of upper-body muscle power after short intensive exercise: comparing boys and men.

PURPOSE: Boys' lower-body muscle power generation (PO) recovers faster than men's following intensive exercise. The purpose of this study was to examine whether boys differ from adult men in recovering from upper-body muscle power generation following intensive exercise. METHODS: Fifteen prepubertal boys (M ± SD age 10.6 ± 1.0 years) and 13 men (31.1 ± 5.0 years) performed two upper-body Wingate Anaerobic Tests (WAnT), separated by either 2-min or 10-min recovery intervals. WAnT parameters, pre-and post-WAnT heart rates (HR), and blood lactate ([La]) were measured during recovery from the WAnTs. RESULTS: Boys' mean power (MP) of the repeated WAnT (WAnT2) following 2- and 10-min recoveries was 97.3 ± 7.2% and 99.4 ± 3.9%, respectively, compared to MP of the first test (WAnT1) (p > 0.05 for both tests). In contrast, in men's MP of the WAnT2 following the 2-min recovery, was significantly lower than that of the WAnT1 (84.4 ± 6.7%, p = 0.0001). While boys' and men's HR recovery after 2 min differed significantly (p = 0.046), no between-group differences were found following the 10-min recovery. Peak [La] in boys was 37-44% lower than that in men (p = 0.002). CONCLUSIONS: The faster recovery of PO in boys after supra-maximal upper-body exercise is partially explained by the lower power generated by boys, attributed in part to a lower anaerobic capacity and to the greater relative contribution of aerobic processes to performance and recovery from anaerobic-type tasks. Further research is needed to determine the physiologic, neurologic and biochemical basis of the rapid muscle power recovery in children.

The choice of freely preferred cadence by trained nonprofessional cyclists may not be characterized by mechanical efficiency.

BACKGROUND: Most cycling studies involve professional cyclists. Because training may affect riding style, it is of interest to determine the physiological basis for the personal choice of cycling cadence in nonprofessional cyclists. METHODS: Eleven nonprofessional (5.2±1.7-year-riding experience) male road cyclists, aged 35.0±11.0 years, underwent four separate laboratory test sessions. The first two sessions included habituation, anthropometry, V˙O2max,$\dot V{{\text{O}}_{\text{2}}}{\text{max}},$ and lactate threshold (LaTH) measurements. Freely preferred cadence at LaTH was determined during the second session (mean±SD=94.7±2.9 rev·min-1). During the third and fourth sessions participants performed LaTH tests at 60 and 95 rev·min-1 in a randomized order, with power output (PO) increments of 25 W every 4 min, up to ~90% of V˙O2max.$\dot V{{\text{O}}_{\text{2}}}{\text{max}}{\text{.}}$ Results: V˙O2,$\dot V{{\text{O}}_{\text{2}}},$ expired ventilation (V˙E),$({\dot V_E}),$ blood lactate (La), and calculated net mechanical efficiency (MEnet) rose with increased PO. At 95 rev·min-1, V˙O2, V˙E,$\dot V{{\text{O}}_2},{\text{ }}{\dot V_{\text{E}}},$ and La were significantly higher than at 60 rev·min-1 at all POs. MEnet at 95 rev·min-1 was lower than at 60 rev·min-1. Mean PO attained at LaTh did not differ significantly between 60 and 95 rev·min-1 (220.9±29.0 and 214.5±9.2 W, respectively). La values at LaTH were higher at 95 rev·min-1 than at 60 rev·min-1 (3.01±0.17 vs. 2.10±0.13 mM, p<0.05, respectively). CONCLUSIONS: Our findings indicate that mechanical and physiological efficiencies may not determine the choice of cycling cadence by nonprofessional cyclists. This choice may reflect the need to maintain endurance at the expense of riding at a lower than optimal riding efficiency.

High Mid-Flow to Vital Capacity Ratio and the Response to Exercise in Children With Congenital Heart Disease.

BACKGROUND: Pulmonary mechanics may play a role in exercise intolerance in patients with congenital heart disease (CHD). A reduced FVC volume could increase the ratio between mid-flow (FEF25-75%) and FVC, which is termed high dysanapsis. The relationship between high dysanapsis and the response to maximum-intensity exercise in children with CHD had not yet been studied. The aim of this work was to examine whether high dysanapsis is related to the cardiopulmonary response to maximum-intensity exercise in pediatric subjects with CHD. METHODS: We retrospectively collected data from 42 children and adolescents with CHD who had either high dysanapsis (ratio >1.2; n = 21) or normal dysanapsis (control) (n = 21) as measured by spirometry. Data extracted from cardiopulmonary exercise test reports included peak values of heart rate, work load, V̇O2 , V̇CO2 , and ventilation parameters and submaximum values, including ventilatory threshold and ventilatory equivalents. RESULTS: There were no significant differences in demographic and clinical parameters between the groups. Participants with high dysanapsis differed from controls in lower median peak oxygen consumption (65.8% vs 83.0% of predicted, P = .02), peak oxygen pulse (78.6% vs 87.8% of predicted, P = .02), ventilatory threshold (73.8% vs 85.3% of predicted, P = .03), and maximum breathing frequency (106% vs 121% of predicted, P = .035). In the high dysanapsis group only, median peak ventilation and tidal volume were significantly lower than 80% of predicted values. CONCLUSIONS: In children and adolescents with corrected CHD, high dysanapsis was associated with a lower ventilatory capacity and reduced aerobic fitness, which may indicate respiratory muscle impairments.

[A NEW FIELD-TEST FOR THE ASSESSMENT OF THE HUMAN ANAEROBIC AND REPEATED SPRINTS CAPABILITY - RELIABILITY AND VALIDITY].

PURPOSE: To examine the reliability and validity of a newly developed anaerobic and repeated sprint (RST0 performance capability. METHODS: A total of 35 untrained adolescent schoolchildren (age range 16-18 years) performed four tests: The newly developed 4 x 30 m RST, the Wingate Anaerobic Test (WAnT) and 200 m and 50 m sprint runs. The reliability of the test was assessed by comparing the test and retest performances of the test. The validity of the 4x30m RST was evaluated by computing the relationships among the various indices of the four studied anaerobic tests, and by comparing the effect of a well-defined anaerobic training program on the performance of the four anaerobic tests. RESULTS: Strong and highly significant relationships were found between the mean (MP) and peak (PP) values of the 4x30 m RST (r = 0.88; p < 0.001), and between the MP of the RST and the two short sprints (50m and 200m) (r = 0.81 and 0.94, respectively; p < 0.011. Somewhat weaker, but still significant relationships were observed between the 4x30 RST and the WAnT indices (r's range = 0.56-0.64; p < 0.05). Such relationships suggest that the energetics of all four tests are closely related. Compared with baseline, the training group demonstrated similar and significant improvement in all four anaerobic tests. No such changes were detected for the control group. CONCLUSIONS: The anaerobic system plays a dominant role in the performance of the new 4x30m RST. Furthermore, the new field test is highly reliable and was found to be valid for quantifying gross anaerobic and repeated sprints performance. Therefore, it can be used in pursuing athletes in a wide range of sports, as well as in some relevant occupations.

Fitness's moderation of the facilitative effect of acute exercise on cognitive flexibility in older women.

A recent study indicated that acute aerobic exercise improves cognitive flexibility in adults. The current study assessed age, habitual physical activity, and physical fitness as moderators of this improvement and examined whether the gains still exist an hour after the exercise session. The alternative-uses test, assessing cognitive flexibility, was administered individually to 20 older (age 63.67 +/- 3.55 yr) and 19 young (age 23.9 +/- 1.22) women before, immediately after, and an hour after a single moderate aerobic-exercise session. Results indicated significant improvement in cognitive flexibility in the older group immediately after the exercise but a decrease at the 1-hr follow-up. Further analysis indicated that physical fitness accounted for this improvement (R = -.622, p < .01). No such differences were observed in the young group. Further studies are needed to examine the duration of this effect, as well as the role of physical fitness as a moderator of it.

The effect of restricted arm swing on energy expenditure in healthy men.

Arm swing in human walking is an active natural motion involving the upper extremities. Earlier studies have described the interrelationship between arms and legs during walking, but the effect of arm swing on energy expenditure and dynamic parameters during normal gait, is inconclusive. The aim of this study was to investigate the effect of restricted arm swing during walking on energy expenditure and spatio-temporal parameters. Fifteen healthy men (aged 19-29 years, height 158-192 cm, weight 50-80 kg) volunteered to walk on a Woodway (Hamburg, Germany) treadmill for 10 min at four different, random velocities, customary walking speed (CWS=100%), slow walking speed (80% CWS), fast walking speed (120% CWS) and very fast walking speed (140% CWS). Participants walked twice at each velocity: once with a natural arm swing and once with restricted arms. Sensor Medics Vmax29 (California, USA), a metabolic system machine measured oxygen consumption. Heart rate was also recorded. Concurrently, selected spatial-temporal parameters were taken. Walking with restricted arms resulted in a significant increase in VO2 consumption (VO2C) (8-34%), heart rate (8-17%) and O2 cost (8-20%). A significant increase in cadence (F=674.71; P<0.000) was accompanied by an equal reduction in stride length (F=748.21; P<0.000). Estimating VO2C based on changes in cadence while speeding and with restricted arms, indicated an 8-22.7% reduction in VO2C. Restricted arm swing seems to increase VO2C, whereas an increase in cadence tends to reduce VO2C to maintain constrained high velocity. The results of this study are relevant to gait efficiency of patients suffering from upper extremity dysfunction such as upper-limbs amputees and Parkinson's disease or in long distance walking of healthy participants carrying loads in their arms.

Thoracic sympathectomy and cardiopulmonary responses to exercise.

The purpose was to study the effect of endoscopic thoracic sympathectomy (ETS) for palmar and/or axillary hyperhidrosis on physiological responses at rest, and during sub-maximal and maximal exercise in ten healthy patients (7 females and 3 males 18-40 years old) with idiopathic palmar and/or axillary hyperhidrosis. T2-T3 thoracoscopic sympathectomy was performed using a simplified one stage bilateral procedure. Physiological variables were recorded at rest and during sub-maximal (steady-state) and maximal treadmill exercise immediately prior to and 70 days (+/-7.5, SD) after bilateral ETS. Exercise performance capacity and peak VO(2) were not found to be different following bilateral ETS than prior to the ETS. However, heart rate was significantly reduced at rest (14%), at sub-maximal exercise (12.3%), and at peak exercise (5.7%), together with a significant increase in oxygen pulse (11.8, 12.7, and 7.8%, respectively). The rate pressure product (RPP) was also significantly reduced following the surgical procedure at all three study stages, while all other physiological variables measured remained unchanged. It is suggested that thoracic-sympathetic denervation affects the heart, sweating, and circulation of the respective denervated region but does not affect exercise performance or mechanical/physiologic efficiency, despite a significant reduction in heart rate (both at rest and during exercise). The latter was, most likely, fully compensated by an increase in stroke volume and less likely by an improved muscle O(2) extraction due to more efficient blood distribution, keeping the work-rate and oxygen uptake unaffected.

The effect of sibutramine intake on resting and exercise physiological responses.

AIM: To evaluate the effect of a short-term sibutramine intake on energy expenditure and on physiological responses during rest, submaximal exercise and maximal exercise in obese women. METHODS: Fifteen healthy obese female volunteers were randomly assigned to either a placebo (n = 6 - control) or sibutramine group (n = 9 - experimental) under double-blind conditions. Each subject was tested under resting conditions and then performed submaximal and maximal exercise tests. Subjects were retested under identical conditions following a 5-day administration of either sibutramine 10 mg x day(-1) or a placebo. All measurements (i.e. weight, body composition, resting energy expenditure, heart rate, respiratory exchange ratio, ventilation, oxygen consumption, carbon dioxide production, systolic blood pressure, diastolic blood pressure and blood lactate concentration) were analyzed using a 2-way ANOVA with repeated measures. RESULTS: Only heart rate during submaximal exercise was significantly different (higher) following short-term sibutramine administration when compared to placebo (p < 0.05). CONCLUSIONS: These data suggest that a recommended daily dose of 10 mg sibutramine does not affect energy expenditure or other selected cardiopulmonary responses during rest, submaximal exercise or maximal exercise. It is, therefore, suggested that weight loss during sibutramine treatment in humans is achieved mostly via a decrease in energy intake rather than through an increase in energy expenditure and thermogenesis.

Gender differences in anaerobic power of the arms and legs--a scaling issue.

PURPOSE: Physiological variables must be scaled for body size differences to permit meaningful comparisons between groups. Using allometric scaling, this study compared the anaerobic performance, using both arms and legs, of men and women. Ten active male and 10 active female subjects performed the leg cycling and arm cranking in a 30-s all-out Wingate test (WAnT). Regional measurements of the legs, gluteal area, arms, and torso taken using dual-energy x-ray absorptiometry (DXA) served as indicators of lower body active musculature (LBAMM) and upper body (UBAMM) active musculature. RESULTS: Body mass (BM) was the best predictor (i.e., r = 0.93-0.96) for peak power (PP) and mean power (MP) generated from sprint cycling and arm cranking. Sex differences for leg and arm power (i.e., PP and MP) were identified in absolute terms and then expressed in ratio to BM(1.0). When the same data were allometrically scaled to BM and expressed as power function ratios (Power;BM(b)), the sex differences in PP and MP for sprint cycling were nullified (female:male ratio x 100: 100-103%), but remained for arm cranking (female:male power ratio x 100: 69-84%). CONCLUSIONS: These results confirmed that anaerobic power of the upper body and lower body were best normalized to BM and, when statistically appropriate methods were used to take into account differences in BM, PP, and MP generated from sprint cycling were similar for both men and women. In contrast, after allometric scaling for BM, men remained more powerful than women for the supramaximal arm cranking task. Qualitative differences in the upper body musculature between men and women are speculated to account for the more powerful performance of men, but confirmatory evidence using noninvasive techniques is warranted.

Preferred transition speed between walking and running: effects of training status.

PURPOSE: This study was conducted to identify the preferred transition speed (PTS) between walking and running and the energetically optimal transition speed (ETOS), in runners and nonrunners. METHODS: A total of 19 young men were asked to walk on a treadmill at 5 km.h(-1). Speed was then increased by 0.2 km.h(-1) every minute. Subjects were instructed to start running at a particular speed they felt was easier. PTS for each subject was determined as the mean of the walk-run and the run-walk transitions. Subjects were also asked to walk and to run for 5 min at each of the following velocities: PTS - 1 km.h(-1), PTS - 0.5 km.h(-1), PTS, PTS + 0.5 km.h(-1), and PTS + 1 km.h(-1). This procedure was performed twice, once walking and once running, at all speeds. Physiologic measurements of oxygen consumption, heart rate, and rate of perceived exertion (RPE) were performed at each stage. EOTS was determined by plotting individual curves for each subject with the energy cost of locomotion as a function of velocity. RESULTS: Preferred transition speed was 7.23 +/- 0.25 and 7.42 +/- 0.25 km.h(-1) for nonrunners and runners, respectively (P > 0.05), and differed significantly (F = 16.47, alpha < 0.001) from the EOTS, which was 8.02 +/- 0.84 km.h(-1) for nonrunners and 7.90 +/- 0.48 km.h(-1) for the runners. No significant differences were found between runners and nonrunners in PTS or EOTS. Running at the PTS resulted in a significantly lower RPE and higher energy cost than walking at the PTS in both groups. CONCLUSION: This study indicates that 1) the preferred PTS is slower than the EOTS, and 2) the PTS and EOTS are not dependent on the aerobic capacity or the training status.

Comparison of thermoregulatory responses to exercise in dry heat among prepubertal boys, young adults and older males.

The purpose of this investigation was to compare the thermoregulatory responses during exercise in a hot climate among three age categories. Eight prepubertal (PP), eight young adult (Y) and eight elderly (O) male subjects cycled at an intensity of 50 +/- 1% of their maximum oxygen uptake (V(O2peak)) for 85 min (three 20 min bouts with three 7 min rest periods) in hot and dry conditions (41 +/- 0.67 degrees C, 21 +/- 1% relative humidity). During the exercise-in-heat protocol, rectal temperature (T(re)) skin temperatures (T(sk)), heart rate (HR), V(O2), V(CO2) V(E), RER, sweat rate, and the number of heat activated sweat glands (HASG) were determined. Despite highest and lowest end-exposure T(re) in the Y and O groups, respectively, the rise in rectal temperature (accounting for differences in baseline T(re)) was similar in all age groups. Changes in body heat storage (DeltaS), both absolute and relative to body mass, were highest in the Y and O groups and lowest in the PP group. While end-session as well as changes in mean skin temperature were similar in all three age groups, HR (absolute and percentage of maximum) was significantly lower for the O compared with the PP and Y groups. Total body as well as per body surface sweating rate was significantly lower for the PP group, while body mass-related net metabolic heat production ((M -- W) kg(-1)) and heat gained from the environment were highest in the PP and lowest in the O group. Since mass-related evaporative cooling (E(sk) kg(-1)) and sweating efficiency (E(sk)/M(sw) kg(-1)) were highest in the PP and lowest in the O group, the mass-dependent heat stored in the body (DeltaS kg(-1)) was lowest in the PP (1.87 +/- 0.03 W kg(-1)) and highest in Y and O groups (2.19 +/- 0.08 and 1.97 +/- 0.11 W kg(-1), respectively). Furthermore, it was calculated that while the O group required only 4.1 +/- 0.5 W of heat energy to raise their body core temperature by 1 degrees C, and the Y group needed 6.9 +/- 0.9 W (1 degrees C)(-1), the PP group required as much as 12.3 +/- 0.7 W to heat up their body core temperature by 1 degrees C. These results suggest that in conditions similar to those imposed during this study, age and age-related characteristics affect the overall rate of heat gain as well as the mechanisms through which this heat is being dissipated. While prepubertal boys seem to be the most efficient thermoregulators, the elderly subjects appear to be the least efficient thermoregulators.

The effects of speech production on physiologic responses during submaximal exercise.

PURPOSE: To investigate the effects of speech production on physiological responses during sub maximal exercise of various intensities. METHODS: Three constant levels running at work intensities corresponding to 65%, 75%, and 85% of the subjects' (N = 14) VO(2) max were performed with and without talking. These loads were chosen to represent the range of training intensities, which are most often used by the general population for improving cardiovascular fitness. During both sessions, various cardiopulmonary variables were measured breath-by-breath. RESULTS: Oxygen uptake, ventilation, breathing frequency, CO(2) production, total respiration cycle time, and expiration time decreased significantly while blood lactate, blood pressure, and end tidal CO(2) increased. There were no significant differences between talking and being silent in heart rate, inspiration time, and in tidal volume. CONCLUSIONS: Speech production during sub maximal exercise results in a significant reduction in minute ventilation and oxygen uptake with an accompanying elevation of lactic acid and blood pressure. These findings are of particular relevance for planning rehabilitation or training programs for ill as well as for healthy populations.