The effects of two levels of caffeine ingestion on excess postexercise oxygen consumption in untrained women

Summary The effects of two levels of caffeine ingestion (5 mg·kg ^–1, CAF1, and 10 mg·kg ^–1, CAF2) on postexercise oxygen consumption was investigated in six untrained women aged 20.5 (SEM 0.5) years. After a test to determine maximal oxygen consumption (VO_2max) each subject underwent three test sessions at 55% VO_2max either in a control condition (CON) or with the CAF1 or CAF2 dose of caffeine. During exercise, oxygen consumption was found to be significantly higher in the CAM and CAF2 trials, compared to CON (P<0.05). During the hour postexercise, oxygen consumption in CAF1 and CAF2 remained significantly higher than in CON (P<0.05). At all times throughout the exercise, free fatty acid (FFA) concentrations were significantly higher in the caffeine trials than in CON. The FFA concentrations 1 h postexercise (+ 60 min) were further elevated above resting values for all three trials. Caffeine ingestion caused the greatest elevation above resting levels being 1.89 (SEM 0.19) mmol·l^–1 and 1.96 (SEM 0.22) mmol·1^–1 for the CAF1 and CAF2 trials, respectively. This was significantly higher (P<0.0001) than the CON level which was 0.97 (SEM 0.19) mmol·l^–1. Respiratory exchange ratio (R) values became significantly lower (P<0.05) in CAF1 and CAF2 compared to CON at the onset of exercise and continued to decrease during the activity. Throughout the recovery period, R values were significantly lower for both caffeine trials compared to CON. The results of this study would suggest that caffeine is useful in significantly increasing metabolic rate above normal levels in untrained women during, as well as after, exercising at 55% VO_2max.     

Some aspects of metabolism following a 35 km road run

Summary The metabolism of eight men (mean: age, 26.0 years; maximal oxygen consumption, 65.0 ml·kg^–1 · min^–1; body fat, 10.3%) was measured on counterbalanced control (baseline values for 8h) and experimental (post 35 km run values for 8 h) days. The excess postexercise volume of oxygen consumed of 32.37 1 and increase in energy used of 594 kJ during the 8 h after completion of the run were equivalent to average increases of 23.7 and 21.1%, respectively, when compared with time-matched controls. Furthermore, the oxygen uptake and energy expenditure were still elevated by 12.7 (P<0.0005) and 9.7% (P=0.001), respectively, at the mod, of this period but the fact that they had returned seline 24 h after the 35 km road run contrasts with some reports in the literature that metabolism is still elevated at this time following less demanding exercise intensities. Rectal temperature was elevated by 2.3° C at the end of the run but the difference had decreased to 0.2°C by 7 h postexercise. The respiratory exchange ratio and changes in blood metabolites (nonesterified fatty acids, glycerol and ketone bodies) indicated a greater postexercise utilisation of fat notwithstanding a 6300 kJ meal ingested on both control and experimental days. The highest measured serum creatine kinase enzyme activity of 1151 U.l^–1 (P< 0.05) occurred 24 h postexercise, as compared with the control value of 145 U · 1^–1, and indicates the possibility of skeletal muscle damage.     

The effect of exercise intensity and duration on the oxygen deficit and excess post-exercise oxygen consumption

Summary Nine males with mean maximal oxygen consumption ( ) =63.0 ml· kg^–1 · min^–1, SD 5.7 and mean body fat = 10.6%, SD 3.1 each completed nine counterbalanced treatments comprising 20, 50 and 80 min of treadmill exercise at 30, 50 and 70% . The OZ deficit, 8 h excess post-exercise oxygen consumption (EPOC) and EPOC:O₂ deficit ratio were calculated for all subjects relative to mean values obtained from 2 control days each lasting 9.3 h. The O₂ deficit, which was essentially independent of exercise duration, increased significantly (P<0.05) with intensity such that the overall mean values for the three 30%, 50% and 70% workloads were 0.83, 1.89 and 3.09 l, respectively. While there were no significant differences (P>0.05) between the three EPOCs after walking at 30% for 20 (1.01 l), 50 (1.43 l) and 80 min (1.041), respectively, the EPOC thereafter increased (P<0.05) with both intensity and duration such that the increments were much greater for the three 70% workloads (EPOC: 20 min=5.68 l; 50 min=10.04 l; 80 min= 14.59 l) than for the three 50% workload (EPOC: 20 min =3.14 l; 50 min=5.19 l; 80 min= 6.10 l). An analysis of variance indicated that exercise intensity was the major determinant of the EPOC since it explained five times more of the EPOC variance than either exercise duration or the intensity times duration interaction. The mean EPOC:O₂ deficit ratio ranged from 0.8 to 4.5 and generally increased with both exercise intensity and duration. These data imply that the EPOC is more than mere repayment of the O₂ deficit because metabolism is increasingly disturbed from resting levels as exercise intensity and duration increase due to other physiological factors occurring after the steady-state has been attained.     

The effects of substrate utilization,manipulated by caffeine,on post-exercise oxygen consumption in untrained female subjects

Summary The effect of substrate utilization manipulated by caffeine on post-exercise oxygen consumption was investigated in five untrained females (age=21±1.5 years), following 90 min of treadmill walking at 55% maximal oxygen consumption. Each subject participated in the two trials (control and experimental) within 2 weeks of each other. Immediately following the measurement of resting oxygen consumption, subjects consumed one of the two test beverages 60 min prior to exercise: 5 mg of caffeine per kg of bodyweight in 200 ml of orange juice (CA) or 200 ml of orange juice (C). Assignment of CA and C was made in a random, double blind fashion. Immediately prior to the exercise phase (0 min) resting oxygen consumption was again measured. Following exercise, subjects returned to the same pre-exercise sitting position where respiratory data was collected over 1 h. No significant differences were found in resting oxygen consumption and respiratory exchange ratio (R) prior to caffeine ingestion (−60 min). One hour after caffeine ingestion (0 min) oxygen consumption and free fatty acid (FFA) levels increased significantly compared to C. During and 1 h following exercise, oxygen consumption and FFA levels were significantly greater, with R values being significantly lower in CA compared to C. These findings provide further evidence that metabolic substrate is somehow implicated in elevating oxygen consumption following exercise cessation.     

Resistance exercise increases postexercise oxygen consumption in nonexercising muscle

This study examined the effect of knee extension resistance exercise on muscle oxygen consumption in nonexercising forearm flexor muscles after exercise. Seven healthy male subjects were performed six sets of unilateral knee extension exercise until exhaustion at 40, 60, and 80% of 1 repetition maximum (RM) on separate days. The values at rest, at the end of exercise, and during recovery after exercise were measured by near-infrared spectroscopy. The at the end of exercise was significantly (P < 0.05) increased by 1.8 ± 0.2, 1.7 ± 0.2, and 1.4 ± 0.3 fold over resting value at 40, 60 and 80% 1RM, respectively. returned to the resting values after 1–5 min of recovery and then showed no further significant change for all exercise intensities. This study suggests that knee extension resistance exercise at 40, 60 and 80% 1RM induced an increase in and that the increase of after exercise returned to resting value in several minutes.     

Plasma sulpho-conjugated catecholamine dynamics up to 8 h after 60-min exercise at 50% and 70% maximal oxygen uptakes

The prolonged effects of steady-state exercise and meals on plasma sulpho-conjugated catecholamines (CA) after exercise were examined. Seven male subjects exercised on 2 separate days for 60 min at 50% and 70% of maximal oxygen uptake ( ) on a cycle ergometer and then rested, for 8 h sitting in an armchair. A control trial without any exercise was also performed. At 2 h after the end of exercise the subjects were given a meal. The plasma free and sulphated CA, oxygen uptake ( ) and heart rate (HR) were all measured before exercise, during exercise and hourly during the 8-h recovery period. The sulphated noradrenaline (NA-S) and adrenaline (A-S) concentrations increased after exercise, and, furthermore, only the NA-S concentrations remained elevated for 6 h after exercise at 50% and for 8 h at 70% trial, compared with the control trial. There were no changes in either the plasma NA-S or A-S concentrations after consuming a meal, whereas the dopamine sulphate concentration demonstrated a dynamic change. A significantly higher excess postexercise was observed at 2 h postexercise at 50% and at 6 h postexercise at 70% trials. The mean HR was still elevated at 6 and 8 h after exercise, which closely correlated with the duration of the elevated NA-S concentrations. These results suggest that sulphated CA, especially NA-S, could represent an additional index of sympathetic nerve activity after exercise, and that a meal containing small amounts of the amines would seem to have no effect on plasma NA-S and A-S concentrations.     

Effect of short-term energy intake level and exercise on oxygen consumption in men

Summary The influence of short-term energy intake and cycle exercise on oxygen consumption in response to a 1.5 MJ test meal was investigated in ten young, adult men. On the morning after a previous day's low-energy intake (LE regimen) of 4.5 MJ, the mean resting oxygen consumption increased by 0.7 ml · kg^–1 · min^–1 after the test meal (P<0.025). After a high-energy intake (HE regimen) of 18.1 MJ, the resting measurement was unchanged (+0.4 ml · kg^–1 · min^–1) after the meal (n.s.). These trends are the reverse of what would be expected if oxygen consumption in response to feeding is a factor in the acute control of body weight. The mean fasting oxygen consumption during cycle exercise at 56% of (constant work) for both LE and HE prior intakes was not different at 31.1 ml · kg^–1 · min^–1. Oxygen consumption during exercise increased after feeding by 0.5 ml · kg^–1 · min^–1 on the LE regimen (n.s.) and decreased by 1.2 ml · kg^–1 · min^–1 on the HE regimen (n.s.). These results are also the reverse of what would be expected if oxygen consumption in response to exercise is related to short-term energy intake.     

Effect of an acute period of resistance exercise on excess post-exercise oxygen consumption: implications for body mass management

Studies have shown metabolism to remain elevated for hours following resistance exercise, but none have gone beyond 16 h, nor have they followed a whole body, high intensity exercise protocol. To examine the duration of excess post-exercise oxygen consumption (EPOC) following a period of heavy resistance exercise, seven healthy men [mean (SD) age 22 (3) years, height 177 (8) cm, mass 83 (10) kg, percentage body fat 10.4 (4.2)%] engaged in a 31 min period of resistance exercise, consisting of four circuits of bench press, power cleans, and squats. Each set was performed using the subject's own predetermined ten-repetition maximum and continued until failure. Oxygen consumption ( ) measurements were obtained at consistent times (34 h pre-, 29 h pre-, 24 h pre-, 10 h pre-, 5 h pre-, immediately post-, 14 h post-, 19 h post-, 24 h post-, 38 h post-, 43 h post-, and 48 h post-exercise). Post-exercise measurements were compared to the baseline measurements made at the same time of day. The was significantly elevated (P<0.05) above baseline values at immediately post, 14, 19, and 38 h post-exercise. Mean daily values for both post-exercise days were also significantly elevated above the mean value for the baseline day. These results suggest that EPOC duration following resistance exercise extends well beyond the previously reported duration of 16 h. The duration and magnitude of the EPOC observed in this study indicates the importance of future research to examine a possible role for high intensity resistance training in a weight management program for various populations. Electronic Publication     

The effects of dietary manipulation upon the respiratory exchange ratio as a predictor of maximum oxygen uptake during fixed term maximal incremental exercise in man

Summary This study examined the effects of dietary manipulation upon the respiratory exchange ratio ( ) as a predictor of maximum oxygen uptake ( ). Seven healthy males performed fixed term maximal incremental treadmill exercise after an overnight fast on three separate occasions. The first test took place after the subjects had consumed their normal mixed diet (45±5% carbohydrate (CHO)) for a period of three days. This test protocol was then repeated after three days of a low CHO diet (3±2% CHO), and again after three days of a high CHO diet (61±5% CHO). Respiratory gases were continuously monitored during each test using an online system. No significant changes in mean exercise oxygen uptake ( ), or maximum functional heart rate (FHR_max) were found between tests. Mean exercise carbon dioxide output ( ) and R were significantly lower than normal after the low CHO diet (bothp<0.001) and significantly higher than normal after the high CHO diet (bothp<0.05). Moreover, compared with the normal CHO diet, the R-time relationship during exercise was at all times significantly (p<0.001) shifted to the right after the low CHO diet, and shifted to the left, being significantly so (p<0.05) over the final 5 min of exercise, after the high CHO diet. As a result, predictions of based on the R-time relationship were similar to recorded after the normal CHO dietary condition (-1.5±1.9%), but higher after the low CHO diet (+14.8±3.9%,p<0.001) and lower after the high CHO diet (–7.0±4.5%,p<0.01). These results indicate that dietary manipulation can significantly affect respiratory gas exchanges during fixed term maximal incremental exercise, and by doing so can significantly influence predictions of based on R.     

Influence of intensity fluctuation on exercise metabolism

This investigation was undertaken to examine the influence of intensity fluctuation on metabolic responses during and after exercise. Twenty-four males and 24 females were randomly assigned into one of the four groups consisting of 12 subjects of equal gender. Each group performed one of four 30-min exercise protocols: (1) cycling at a constant power output of 75 W (P1), (2) cycling with power output alternating between 50 and 100 W every 5 min (P2), (3) same as P2 except power output was alternated in a reverse order (P3), and (4) same as P2 except power output was alternated between 25 and 125 W (P4). Each exercise session was followed by a 25-min recovery and all protocols yielded the same mechanical work. Oxygen uptake (VO₂), heart rate (HR), respiratory exchange ratio (RER), and plasma lactate concentrations ([La]) were measured at rest and during exercise and recovery. Ratings of perceived exertion (RPE) were recorded during exercise only. During exercise, VO₂, HR and RPE did not differ across the four protocols. RER was higher (P < 0.05) in P4 than P1 and P2. [La] was higher (P < 0.05) in P4 than P1 and P3. During recovery, VO₂ were lower (P < 0.05) in P1 than P2, P3, and P4, while [La] was higher in P4 than P3. When the total workload was equated, intensity fluctuation exerted no added effect upon metabolic responses during exercise, but provoked greater energy expenditure following exercise. Reversing the order or increasing the magnitude of intensity fluctuation would not further alter metabolic consequences.     

The respiratory system as an exercise limiting factor in normal trained subjects

Summary Recently, we have shown that an untrained respiratory system does limit the endurance of submaximal exercise (64% peak oxygen consumption) in normal sedentary subjects. These subjects were able to increase breathing endurance by almost 300% and cycle endurance by 50% after isolated respiratory training. The aim of the present study was to find out if normal, endurance trained subjects would also benefit from respiratory training. Breathing and cycle endurance as well as maximal oxygen consumption ( ) and anaerobic threshold were measured in eight subjects. Subsequently, the subjects trained their respiratory muscles for 4 weeks by breathing 85-1601 · min^–1 for 30 min daily. Otherwise they continued their habitual endurance training. After respiratory training, the performance tests made at the beginning of the study were repeated. Respiratory training increased breathing endurance from 6.1 (SD 1.8) min to about 40 min. Cycle endurance at the anaerobic threshold [77 (SD 6) % ] was improved from 22.8 (SD 8.3) min to 31.5 (SD 12.6) min while and the anaerobic threshold remained essentially the same. Therefore, the endurance of respiratory muscles can be improved remarkably even in trained subjects. Respiratory muscle fatigue induced hyperventilation which limited cycle performance at the anaerobic threshold. After respiratory training, minute ventilation for a given exercise intensity was reduced and cycle performance at the anaerobic threshold was prolonged. These results would indicate the respiratory system to be an exercise limiting factor in normal, endurance trained subjects.     

Running economy of elite surf iron men and male runners, on soft dry beach sand and grass

The primary aim of this study was to measure the energetics of six elite surf iron men (who participate in regular sand running training), performing steady-state running trials on grass in shoes at 8, 11 and 14 km·h^–1, and on sand bare foot and in shoes, at both 8 and 11 km·h^–1. The net total energy cost (EC, J·kg^–1·m^–1) was determined from the net steady-state oxygen consumption and respiratory exchange ratio (net aerobic EC) plus net lactate accumulation (net anaerobic EC). For the sand barefoot and sand in shoes running trials at 8 and 11 km·h^–1, net aerobic EC and total net EC (but not anaerobic EC) were significantly greater (P<0.001) than the grass running trial values. No differences (P>0.05) existed between the sand barefoot and sand in shoes trials. These measures were compared with data obtained from eight well-trained male recreational runners who performed the same protocol in a previous study, but who were not accustomed to running on sand. Comparisons of net aerobic EC between the two groups for the surface conditions were not significantly different (P>0.05). For net anaerobic EC, the iron man values were significantly less (P<0.02) than the recreational runner values. For net total EC, the iron man values were less than the recreational runner values, but the differences were only significant when both groups ran on sand barefoot (P<0.03: on grass P=0.158; on sand in shoes P=0.103). The lower lactate accumulation values recorded for the iron men on both grass and sand may indicate that running on sand potentially reduces metabolic fatigue when running on firm or soft surfaces. Electronic Publication     

The effects of a single bout of exercise on resting energy expenditure and respiratory exchange ratio

We investigated the effects of a single bout of aerobic and resistance exercise of similar relative intensity and duration on resting energy expenditure (REE) and substrate utilisation. Ten young healthy males volunteered [age 22 (1.8) years, weight 76 (7.9) kg, height 176 (4.1) cm, percentage body fat 10.5 (4.0)%; mean (SEM)]. They randomly underwent three conditions in which they either lifted weights for 60 min at 70–75% of 1-RM (WL), ran for 60 min at 70–75% of maximal oxygen intake (R) or did not exercise (C). REE and substrate utilisation, determined via respiratory exchange ratio (R), were measured prior to exercise, and 10, 24, 48 and 72 h post-exercise. It was revealed that REE was significantly elevated (P<0.05) 10 and 24 h after the end of WL [2,124 (78) and 2,081 (76) kcal, respectively] compared to pre-exercise [1,972 (82) kcal]. REE was also significantly increased (P<0.05) 10 and 48 h after the completion of R [2,150 (73) and 1,995 (74) kcal, respectively] compared to pre-exercise data [1,862 (70) kcal]. R was lower 10 and 24 h following either WL or R [0.813 (0.043); 0.843 (0.040) and 0.818 (0.021); 0.832 (0.021), respectively] compared to baseline measurements [0.870 (0.025) and 0.876 (0.04), respectively]. Creatine kinase was significantly elevated (P<0.05) 24 h after both WL and R, whereas delayed onset muscle soreness became significantly elevated (P<0.05) 24 h after only WL. There were no significant changes for any treatment in thyroid hormones (T₃ and T₄). These results suggest that a single bout of either WL or R exercise, characterised by the same relative intensity and duration, increase REE and fat oxidation for at least 24 h post-exercise.     

Muscle phosphocreatine and pulmonary oxygen uptake kinetics in children at the onset and offset of moderate intensity exercise

To further understand the mechanism(s) explaining the faster pulmonary oxygen uptake kinetics found in children compared to adults, this study examined whether the phase II kinetics in children are mechanistically linked to the dynamics of intramuscular PCr, which is known to play a principal role in controlling mitochondrial oxidative phosphorylation during metabolic transitions. On separate days, 18 children completed repeated bouts of moderate intensity constant work-rate exercise for determination of (1) PCr changes every 6 s during prone quadriceps exercise using ³¹P-magnetic resonance spectroscopy, and (2) breath by breath changes in during upright cycle ergometry. Only subjects (n = 12) with 95% confidence intervals ≤±7 s for all estimated time constants were considered for analysis. No differences were found between the PCr and phase II time constants at the onset (PCr 23 ± 5 vs. or offset (PCr 28 ± 5 vs. of exercise. The average difference between the PCr and phase II time constants was 4 ± 4 s for the onset and offset responses. Pooling of the exercise onset and offset responses revealed a significant correlation between the PCr and time constants (r = 0.459, P = 0.024). The close kinetic coupling between the and PCr responses at the onset and offset of exercise in children is consistent with our current understanding of metabolic control and suggests that an age-related modulation of the putative phosphate linked controller(s) of mitochondrial oxidative phosphorylation may explain the faster kinetics found in children compared to adults.     

The effect of rest interval length on metabolic responses to the bench press exercise

The purpose of this study was to examine the effects of different rest interval (RI) lengths on metabolic responses to the bench press. Eight resistance-trained men performed 10 randomized protocols [five sets of bench press with 75 or 85% of 1RM for ten (10REP) and five repetitions (5REP), respectively, using different RI (30 s, 1, 2, 3, 5 min)]. Oxygen consumption (VO₂) was measured during exercise and for 30 min post exercise. For 30-s and 1-min RI: reductions (15–55%) in resistance and volume were observed (set 5 < 4 < 3 < 2 < 1). For 2-min RI: performance was maintained during the first two sets but was reduced by 8–29% during sets 3–5. For 3-min RI: a reduction was observed in volume where sets 4 and 5 were lower than sets 1–3 (∼21%). For 5-min RI: only a reduction in set 5 was observed. Mean VO₂ and ventilation (V _E) were progressively higher as RI length was shortened. VO₂ area under the curve indicated 10REP > 5REP for all RI except 1-min. Respiratory exchange ratio (RER) was elevated similarly for each protocol. Post exercise, VO₂, V _E, and RER were elevated through 30 min. No differences between RI were observed following 10REP; however, VO₂ after 30-s was higher than 2-, 3-, and 5-min and 1-min was higher than 5-min during 5REP. Fatigue rate was correlated (r = 0.30–0.49) to all metabolic variables. A continuum of performance reductions and metabolic responses were observed. The largest reductions in performance occurred with very short RI (<1 min), and performance was maintained during the first 3–4 sets when 3- and 5-min RI were used.     

Maximum oxygen consumption in dogs during muscular exercise and cold exposure

Maximum oxygen consumption for a short exhaustive work (Ex max) and for a severe cold stress (Ex max) were investigated in 8 dogs. Heart rate, plasma catecholamines and substrate concentrations were measured under both conditions. Mean C was lower than mean Ex max. Heart rate and plasma lactate were also lower during cold exposure than during exercise. Average plasma epinephrine concentrations were not significantly different and average plasma norepinephrine concentrations were similar under C and Ex max conditions. A positive correlation was found between plasma lactate and epinephrine concentrations measured under both conditions.It may be assumed that maximum oxygen consumption during muscular exercise is higher than during shivering thermogenesis. This difference does not seem to be due to differences in the involvement of the sympathico-adreno-medullary system.     

The effects of a high carbohydrate diet on postprandial energy expenditure during exercise in rats

Summary Whether or not a high intake of carbohydrate increases postprandial energy expenditure during exercise was studied in rats. The rats were meal-fed regularly twice a day (0800–0900 hours and 1800–1900 hours) on either a high carbohydrate (CHO) (carbohydrate/fat/protein = 70/5/25, % of energy) or high fat (FAT) (35/40/25) diet for 12 days. On the final day of the experiment, all of the rats in each dietary group were fed an evening meal containing equal amounts of energy (420 kJ · kg^–1 body mass). After the meal, they were divided into three subgroups: pre-exercise control (PC), exercise (EX), and resting control (RC). The PC-CHO and PC-FAT groups were sacrificed at 2030 hours. The EX-CHO and EX-FAT groups were given a period of 3-h swimming, and then sacrificed at 2330 hours. The RC-CHO and RC-FAT groups rested after the meal and were sacrificed at 2330 hours. Total energy expenditure during the period 1.5 h from the commencement of exercise was higher in EX-CHO than in EX-FAT. The respiratory exchange ratio was also higher in EX-CHO than in EX-FAT, suggesting enhanced carbohydrate oxidation in the former. Compared with both PC-FAT and RC-FAT, the liver glycogen content of EX-FAT rats was significantly decreased by exercise. On the other hand, the liver glycogen content of both EX-CHO and RC-CHO was higher than that of PC-CHO rats. The glycogen content of soleus muscle of EX-FAT was slightly decreased during exercise, however, that of EX-CHO increased significantly. Thus postprandial energy expenditure during exercise was higher in the rats fed the CHO diet than in those fed the FAT diet, which could have been related to the increase of both liver and muscle glycogen storage during exercise in the former.     

The effects of cigarette smoking on maximal oxygen consumption and selected physiological responses of elite team sportsmen

Summary The acute and chronic effects of cigarette smoking on selected physiological responses were determined in seven well-trained non-smokers and seven well-trained habitual smokers. Non-smokers and smokers did not differ significantly with respect to maximal oxygen consumption ( ). The acute effect of smoking two cigarettes immediately prior to a graded exercise stress test on a treadmill ergometer did not significantly alter the of either group. However, the time taken for non-smokers to reach exhaustion decreased significantly (F=5.381, P<0.05) by a mean of 0.64 min. Smokers recorded lower scores for forced vital capacity (FVC) and forced expiratory volume in the 1st s exhalation (FEV₁) than non-smokers. Only the mean FVC of smokers recorded 5 min post-exercise was significantly altered by pre-exercise smoking. No differences were found between the resting heart rates (HR) of non-smokers and smokers. Smoking two cigarettes significantly (F=44.720, P<0.01) increased the mean resting HR of smokers and non-smokers by 15.8 beats·min^–1 and 15.6 beats·min^–1 respectively. No alteration to the exercise HR of either group was found under smoking conditions of the tests.