Energy expenditure during bicycling

This study was designed to measure the O2 uptake (VO2) of cyclists while they rode outdoors at speeds from 32 to 40 km/h. Regression analyses of data from 92 trials using the same wheels, tires, and tire pressure with the cyclists riding in their preferred gear and in an aerodynamic position indicated the best equation (r = 0.84) to estimate VO2 in liters per minute VO2 = -4.50 + 0.17 rider speed + 0.052 wind speed + 0.022 rider weight where rider and wind speed are expressed in kilometers per hour and rider weight in kilograms. Following another rider closely, i.e., drafting, at 32 km/h reduced VO2 by 18 +/- 11%; the benefit of drafting a single rider at 37 and 40 km/h was greater (27 +/- 8%) than that at 32 km/h. Drafting one, two, or four riders in a line at 40 km/h resulted in the same reduction in VO2 (27 +/- 7%). Riding at 40 km/h at the back of a group of eight riders reduced VO2 by significantly more (39 +/- 6%) than drafting one, two, or four riders in a line; drafting a vehicle at 40 km/h resulted in the greatest decrease in VO2 (62 +/- 6%). VO2 was also 7 +/- 4% lower when the cyclists were riding an aerodynamic bicycle. An aerodynamic set of wheels with a reduced number of spokes and one set of disk wheels were the only wheels to reduce VO2 significantly while the cyclists were riding a conventional racing bicycle at 40 km/h.(ABSTRACT TRUNCATED AT 250 WORDS)     

Energy expenditure comparison between walking and running in average fitness individuals

Increased energy expenditure (EE) is a key component in maintaining a healthy body mass. Walking and running are 2 common aerobic activities that increase EE above resting values. The purpose of this study was to compare the EE of individuals with average fitness during a walk and run for 1600 meters at 86 m·min(-1) and 160 m·min(-1), respectively. In addition, EE after the walk and run was compared. Fifteen females and 15 males (21.90 ± 2.52 y; 168.89 ± 11.20 cm; 71.01 ± 17.30 kg; 41.51 ± 6.31 ml(-1)·kg(-1)·min(-1)) volunteered to participate. Each participant completed a VO2max test. In addition, oxygen consumption was measured at rest for 10 minutes before exercise, during the walk and run, and after the walk and run for 30 minutes of recovery. EE during exercise was 372.54 ± 78.16 kilojoules for the walk and 471.03 ± 100.67 kilojoules for the run. Total EE including excess postexercise EE was 463.34 ± 80.38 kilojoules and 664.00 ± 149.66 kilojoules for the walk and run, respectively. Postexercise EE returned to resting values 10 minutes after the walk and 15 minutes after the run. Walking and running are both acceptable activities that increase EE above rest and can be performed without the expense of a health club membership and meet adequate kilojoule expenditure according to American College of Sports Medicine guidelines.     

Energy expenditure during simulated rowing

Metabolic function was measured by open-circuit spirometry for 310 competitive oarsmen during and following a 6-min maximal rowing ergometer exercise. Aerobic and anaerobic energy contributions to exercise were estimated by calculating exercise O2 cost and O2 debt.O2 debt was measured for 30 min of recovery using oxygen consumption (Vo2) during light rowing as the base line. Venous blood lactates were analyzed at rest and at 5 and 30 min of recovery. Maximal ventilation volumes ranged from 175 to 22l 1/min while Vo2 max values averaged 5,950 ml/min and 67.6 ml/kg min. Maximal venous blood lactates ranged from 126 to 240 mg/100 ml. Average O2 debt equaled 13.4 liters. The total energy cost for simulated rowing was calculated at 221.5 kcal assuming 5 kcal/l O2 with aerobic metabolism contributing 70% to the total energy released and anaerobiosis providing the remaining 30%. Vo2 values for each minute of exercise reflect a severe steady state since oarsmen work at 96-98% of maximal aerobic capacity. O2 debt and lactate measurements attest to the severity of exercise and dominance of anaerobic metabolism during early stages of work.     

Plasma volume changes in middle-aged male and female subjects during marathon running

Circulatory fluid shifts were studied in middle-aged runners (6 males and 5 females, ages 32-58 yr) during a 42.2-km marathon race run in mild weather (dry-bulb temperature = 17.5-20.4 degrees C). Running times for the subjects were 3:12-4:40 (mean values were 3:34 for males and 4:10 for females). Venous blood samples were taken without stasis in all subjects seated at rest before the start of the race and within 3 min of finishing; eight of the subjects also paused for samples at 6 and 27 km during the race. At 6 km, body weight loss averaged less than 1%, whereas plasma volume (PV) had decreased by 6.5% in male subjects and 8.6% in female subjects. By the end of the race, hypohydration had reached 3.2% in male subjects and 2.9% in female subjects, but PV in both groups remained stable. Sweat rates during the race averaged 545 and 429 g X m-2 X h-1 for male and female subjects, respectively, with ad lib. water intake replacing 21-72% of fluid loss. Increases in plasma protein concentration throughout the race reflected the observed initial decrease in PV. The interpretation of PV responses to exercise and/or hypohydration is critically dependent on selection of base-line conditions; we were able to control for posture-exercise effects by treating the early exercise (6 km) sample as the base line for examining the effects of later fluid loss. Under these conditions, the vascular compartment resisted volume depletion. The ability to maintain stable PV can be explained in part by relationships among oncotic and hydrostatic pressures in the intra- and extravascular fluid compartments.     

Energy expenditure and cardiorespiratory responses at the transition between walking and running

We investigated whether the spontaneous transition between walking and running during moving with increasing speed corresponds to the speed at which walking becomes less economical than running. Seven active male subjects [mean age, 23.7 (SEM 0.7) years, mean maximal oxygen uptake ( ), 57.5 (SEM 3.3) ml·kg ^–1·min ^–1, mean ventilatory threshold (VTh), 37.5 (SEM 3) ml·kg ^–1 ·min ^–1] participated in this study. Each subject performed four exercise tests separated by 1-week intervals: test 1, and VTh were determined; test 2, the speed at which the transition between walking and running spontaneously occurs (ST) during increasing speed (increases of 0.5 km·h ^–1 every 4 min from 5 km·h ^–1) was determined; test 3, the subjects were constrained to walk for 4 min at ST, at ST ± 0.5 km·h ^–1 and at ST ± 1 km·h ^–1; and test 4, the subjects were constrained to run for 4 min at ST, at ST±0.5 km·-h ^–1 and at ST±1 km·h ^–1. During exercise, oxygen uptake ( ), heart rate (HR), ventilation ( ), ventilatory equivalents for oxygen and carbon dioxide (% MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGabmOvayaaca% WaaSbaaSqaaiaabweaaeqaaOGaai4laiqadAfagaGaamaaBaaaleaa% caqGYaaabeaakiaacYcacaqGGaGaaeiiaiqadAfagaGaamaaBaaale% aacaqGfbaabeaakiaac+caceWGwbGbaiaacaqGdbGaae4tamaaBaaa% leaacaaIYaaabeaaaaa!4240!\[\dot V_{\text{E}} /\dot V_{\text{2}} ,{\text{ }}\dot V_{\text{E}} /\dot V{\text{CO}}_2 \]), respiratory exchange ratio (R), stride length (SL), and stride frequency (SF) were measured. The results showed that: ST occurred at 2.16 (SEM 0.04) m·s ^–1; , HR and speed at ST were significantly lower than the values measured at VTh (P< 0.001, P< 0.001 and P< 0.05, respectively); changed significantly with speed (P< 0.001) but was greater during running than walking below ST (ST minus 1 km·h ^–1, P< 0.001; ST minus 0.5 km·h ^–1, P< 0.05) with the converse above ST (ST.plus 1 km·h ^–1, P<0.05), whereas at ST the values of were very close [23.9 (SEM 1.1) vs 23.7 (SEM 0.8) ml·kg ^–1 · min ^–1 not significant, respectively, for walking and running]; SL was significantly greater during walking than running (P<0.001) and SF lower (P<0.001); and HR and were significantly greater during running than walking below ST (ST minus 1 km·h ^–1, P<0.01; ST minus 0.5 km·h ^–1, P{<0.05) with the converse above ST (ST plus 1 km·h ^–1, P·< 0.05), whereas no difference appeared for and R between the two types of locomotion. We concluded from this study that ST corresponded to the speed at which the energy expenditure of running became lower than the energy expenditure of walking but that the mechanism of the link needed further investigation.     

Thermoregulation during marathon running in cool, moderate, and hot environments.

A well-trained subject, age 38, ran continously for periods ranging from 60 to 165 min on a motor-driven treadmill at 255.7 m/min while confronted with an airflow equivalent to running speed in cool, moderate, and hot environments. After a period of intensive heat acclimatization, treadmill runs were repeated in the moderate and hot conditions. Measurements were also obtained outdoors in a competitive marathon race. Sweat rate (SR) and mean skin temperature (Ts) were linearly related to Tdb. Acclimatization did not alter VO2max or metabolic rate during the treadmill runs, but heart rat (HR),rectal temperature (Tre), and Ts were lower, SR was higher, and maximal run duration longer in the hot environment, postacclimatization. Maximum runs in the hot environment were terminated by a spiralling increase in Tre to hyperthermic levels, due largely to a marked reduction in cutaneous blood flow, probably reflecting cardiovascular overload from the combined muscular and thermoregulatory blood flow demands, coupled with the effects of progressive dehydration. Utilizing partitional calorimetry and the subject's metabolic heat production, two examples of limiting environmental conditions for his marathon running speed were given.     

Energy expenditure during bench press and squat exercises

Despite the popularity of resistance training (RT), an accurate method for quantifying its metabolic cost has yet to be developed. We applied indirect calorimetry during bench press (BP) and parallel squat (PS) exercises for 5 consecutive minutes at several steady state intensities for 23 (BP) and 20 (PS) previously trained men. Tests were conducted in random order of intensity and separated by 5 minutes. Resultant steady state VO2 data, along with the independent variables load and distance lifted, were used in multiple regression to predict the energy cost of RT at higher loads. The prediction equation for BP was Y' = 0.132 + (0.031)(X1) + (0.01)(X2), R2 = 0.728 and S(xy) = 0.16; PS can be predicted by Y' = -1.424 + (0.022)(X1) + (0.035)(X2), R2 = 0.656 and S(xy) = 0.314; where Y' is VO2 X1 is the load measured in kg and X2 is the distance in cm. Based on a respiratory exchange ratio (RER) of 1.0 and a caloric equivalent of 5.05 kcal x L(-1), VO2 was converted to caloric expenditure (kcal x min(-1)). Using those equations to predict caloric cost, our resultant values were significantly larger than caloric costs of RT reported in previous investigations. Despite a potential limitation of our equations to maintain accuracy during very high-intensity RT, we propose that they currently represent the most accurate method for predicting the caloric cost of bench press and parallel squat.     

Beta-endorphin activity and hypercapnic ventilatory responsiveness after marathon running

To investigate the hypothesis that endurance exercise may lead to a decrease in ventilatory chemosensitivity as possibly mediated by an increase in endogenous beta-endorphins, we measured hypercapnic ventilatory responsiveness (HCVR) and circulating beta-endorphin immunoreactivity in six runners before and after a marathon (42.2 km) race and after administration of 10 mg iv naloxone. Similar testing was performed at identical time periods on the day before the marathon as control data. On each occasion, HCVR was measured twice 15 min apart, and the mean value was used for analysis. Six active (training distance 50-104 km/wk) and experienced (no. of marathons completed, 1-25) runners participated in the study. There were no significant changes in beta-endorphin activity or HCVR on the control day. All runners experienced a rise in beta-endorphin activity from premarathon (21.3 +/- 16.0 pg/ml) to immediate postmarathon (89.6 +/- 84.9 pg/ml) values (P less than 0.05). However, HCVR showed no significant change at any of the three testing periods on the marathon day. To investigate whether a time delay may have affected the lack of response to naloxone, additional testing was performed in five subjects, except that 10 mg iv naloxone was given within 10 min after completion of the marathon, and then HCVR was measured. Although there was a greater than fourfold increase in beta-endorphin immunoreactivity after the marathon, there was no significant change in HCVR after naloxone administration. We conclude that natural increases in endogenous beta-endorphin activity associated with marathon running do not modulate central chemosensitivity.