Energetics of kayaking at submaximal and maximal speeds

The energy cost of kayaking per unit distance (C(k), kJ x m(-1)) was assessed in eight middle- to high-class athletes (three males and five females; 45-76 kg body mass; 1.50-1.88 m height; 15-32 years of age) at submaximal and maximal speeds. At submaximal speeds, C(k) was measured by dividing the steady-state oxygen consumption (VO(2), l x s(-1)) by the speed (v, m x s(-1)), assuming an energy equivalent of 20.9 kJ x l O(-1)(2). At maximal speeds, C(k) was calculated from the ratio of the total metabolic energy expenditure (E, kJ) to the distance (d, m). E was assumed to be the sum of three terms, as originally proposed by Wilkie (1980): E = AnS + alphaVO(2max) x t-alphaVO(2max) x tau(1-e(-t x tau(-1))), were alpha is the energy equivalent of O(2) (20.9 kJ x l O(2)(-1)), tau is the time constant with which VO(2max) is attained at the onset of exercise at the muscular level, AnS is the amount of energy derived from anaerobic energy utilization, t is the performance time, and VO(2max) is the net maximal VO(2). Individual VO(2max) was obtained from the VO(2) measured during the last minute of the 1000-m or 2000-m maximal run. The average metabolic power output (E, kW) amounted to 141% and 102% of the individual maximal aerobic power (VO(2max)) from the shortest (250 m) to the longest (2000 m) distance, respectively. The average (SD) power provided by oxidative processes increased with the distance covered [from 0.64 (0.14) kW at 250 m to 1.02 (0.31) kW at 2000 m], whereas that provided by anaerobic sources showed the opposite trend. The net C(k) was a continuous power function of the speed over the entire range of velocities from 2.88 to 4.45 m x s(-1): C(k) = 0.02 x v(2.26) (r = 0.937, n = 32).     

Effects of prolonged cycle ergometer exercise on maximal muscle power and oxygen uptake in humans

The mechanical power (W_tot, W·kg^–1) developed during ten revolutions of all-out periods of cycle ergometer exercise (4–9 s) was measured every 5–6 min in six subjects from rest or from a baseline of constant aerobic exercise [50%–80% of maximal oxygen uptake (VO_2max)] of 20–40 min duration. The oxygen uptake [VO₂ (W·kg^–1, 1 ml O₂ = 20.9 J)] and venous blood lactate concentration ([la]_b, mM) were also measured every 15 s and 2 min, respectively. During the first all-out period, W_tot decreased linearly with the intensity of the priming exercise (W_tot = 11.9–0.25·VO₂). After the first all-out period (i greater than 5–6 min), and if the exercise intensity was less than 60% VO_2max, W_tot, VO₂ and [la]_b remained constant until the end of the exercise. For exercise intensities greater than 60% VO_2max, VO₂ and [la]_b showed continuous upward drifts and W_tot continued decreasing. Under these conditions, the rate of decrease of W_tot was linearly related to the rate of increase of V [(d W_tot/dt) (W·kg^–1·s^–1) = 5.0·10^–5 –0.20·(d VO₂/dt) (W·kg^–1·s^–1)] and this was linearly related to the rate of increase of [la]_b [(d VO₂/dt) (W·kg^–1·s^–1) = 2.310^–4 + 5.910^–5·(d [la]_b/dt) (mM·s^–1)]. These findings would suggest that the decrease of W_tot during the first all-out period was due to the decay of phosphocreatine concentration in the exercising muscles occurring at the onset of exercise and the slow drifts of VO₂ (upwards) and of W_tot (downwards) during intense exercise at constant W_tot could be attributed to the continuous accumulation of lactate in the blood (and in the working muscles).     

Physiological determinants of best performances in human locomotion

In human locomotion, the metabolic power required (E) to cover a given distance d, in the time t is set by the product of the energy cost of the locomotion (C), i.e. the amount of metabolic energy spent to move over one unit of distance, and the speed (v = d t(-1)): E = Cv = Cdt(-1). Since, for any given d, v is a decreasing function of t and C is either constant or increases with v, it necessarily follows that E is larger the smaller the value of t. Thus, for any given distance and subject, the shortest time will be achieved when E is equal to the individual maximal metabolic power (Emax). In turn, Emax is a decreasing function of t: it depends upon the subject's maximal aerobic power (MAP) and on the maximal amount of energy derived from the full utilisation of anaerobic energy stores (AnS). So, if the relationship between C and (v) in the locomotion at stake and the subject's MAP and AnS are known, his best performance time (BPT) over any given distance can be obtained by solving the equality Emax(t) = E(t). This approach has been applied to estimate individual BPTs in running and cycling. In this paper, the above approach will be used to quantify the role of C, MAP, and AnS in determining BPTs for running, track cycling and swimming. This has been achieved by calculating the changes in BPT obtained when each variable, or a combination thereof, is changed by a given percentage. The results show that in all the three types of locomotion, regardless of the speed, the changes in BPT brought about by changes of C alone account for 45-55% of the changes obtained when all three variables (C, MAP and AnS) are changed by the same amount.     

Oxygen uptake during swimming in a hypobaric hypoxic environment

The purpose of this study was to determine oxygen uptake (VO2) at various water flow rates and maximal oxygen uptake (VO2max) during swimming in a hypobaric hypoxic environment. Seven trained swimmers swam in normal [N; 751 mmHg (100.1 kPa)] and hypobaric hypoxic [H; 601 mmHg (80.27 kPa)] environments in a chamber where atmospheric pressure could be regulated. Water flow rate started at 0.80 m.s-1 and was increased by 0.05 m.s-1 every 2 min up to 1.00 m.s-1 and then by 0.05 m.s-1 every minute until exhaustion. At submaximal water flow rates, carbon dioxide production (VCO2), pulmonary ventilation (VE) and tidal volume (VT) were significantly greater in H than in N. There were no significant differences in the response of submaximal VO2, heart rate (fc) or respiratory frequency (fR) between N and H. Maximal VE, fR, VT, fc, blood lactate concentration and water flow rate were not significantly different between N and H. However, VO2max under H [3.65 (SD 0.11) l.min-1] was significantly lower by 12.0% (SD 3.4)% than that in N [4.15 (SD 0.18) l.min-1]. This decrease agrees well with previous investigations that have studied centrally limited exercise, such as running and cycling, under similar levels of hypoxia.     

A new approach to assessing maximal aerobic power in children: the Odense School Child Study

In two experiments maximal aerobic power (VO2max) calculated from maximal mechanical power (Wmax) was evaluated in 39 children aged 9-11 years. A maximal multi-stage cycle ergometer exercise test was used with an increase in work load every 3 min. In the first experiment oxygen consumption was measured in 18 children during each of the prescribed work loads and a correction factor was calculated to estimate VO2max using the equation VO2max = 12.Wmax + 5.weight. An appropriate increase in work rate based on height was determined for boys (0.16 W.cm-1) and girls (0.15 W.cm-1) respectively. In the second experiment 21 children performed a maximal cycle ergometer exercise test twice. In addition to the procedure in the first experiment a similar exercise test was performed, but without measurement of oxygen uptake. Calculated VO2max correlated significantly (p less than 0.01) with those values measured in both boys (r = 0.90) and girls (r = 0.95) respectively, and the standard error of estimation for VO2max (calculated) on VO2max (measured) was less than 3.2%. Two expressions of relative work load (%VO2max and %Wmax) were established and found to be closely correlated. The relative work load in %VO2max could be predicted from the relative work load in %Wmax with an average standard error of 3.8%. The data demonstrate that calculated VO2max based on a maximal multi-stage exercise test provides an accurate and valid estimate of VO2max.     

Energy cost of running in similarly trained men and women

The energy demand of running on a treadmill was studied in different groups of trained athletes of both sexes. We have not found any significant differences in the net energy cost (C) during running (expressed in J.kg-1.m-1) between similarly trained groups of men and women. For men and women respectively in adult middle distance runners C = 3.57 +/- 0.15 and 3.65 +/- 0.20, in adult long-distance runners C = 3.63 +/- 0.18 and 3.70 +/- 0.21, in adult canoeists C = 3.82 +/- 0.34 and 3.80 +/- 0.24, in young middle-distance runners C = 3.84 +/- 0.18 and 3.78 +/- 0.26 and in young long-distance runners C = 3.85 +/- 0.12 and 3.80 +/- 0.24. This similarity may be explained by the similar training states of both sexes, resulting from the intense training which did not differ in its relative intensity and frequency between the groups of men and women. A negative relationship was found between the energy cost of running and maximal oxygen uptake (VO2max) expressed relative to body weight (for men r = -0.471, p less than 0.001; for women r = -0.589, p less than 0.001). In contrast, no significant relationship was found in either sex between the energy cost of running and VO2max. We conclude therefore that differences in sports performance between similarly trained men and women are related to differences in VO2max.kg-1. The evaluation of C as an additional characteristic during laboratory tests may help us to ascertain, along with other parameters, not only the effectiveness of the training procedure, but also to evaluate the technique performed.     

Determination of the velocity associated with the longest time to exhaustion at maximal oxygen uptake

The so-called velocity associated with VO2max, defined as the minimal velocity which elicits VO2max in an incremental exercise protocol (v(VO2max)), is currently used for training to improve VO2max. However, it is well known that it is not the sole velocity which elicits VO2max and it is possible to achieve VO2max at velocities lower and higher than v(VO2max). The goal of this study was to determine the velocity which allows exercise to be maintained the longest time at v(VO2max). Using the relationship between time to exhaustion at VO2max in the all-out runs at 90%, 100%, 120% and 140% of v(VO2max) and distance run at VO2max, the velocity which elicits the longest time to exhaustion at VO2max (CV') was determined. For the six subjects tested (physical education students), this velocity was not significantly different from v(VO2max) (16.96+/-0.92 km x h(-1) vs 17.22+/-1.12 km x h(-1), P = 0.2 for CV' and v(VO2max), respectively) and these two velocities were correlated (r = 0.88, P = 0.05).     

Peak power output predicts maximal oxygen uptake and performance time in trained cyclists

The purposes of this study were firstly to determine the relationship between the peak power output (Wpeak) and maximal oxygen uptake (VO2max) attained during a laboratory cycling test to exhaustion, and secondly to assess the relationship between Wpeak and times in a 20-km cycling trial. One hundred trained cyclists (54 men, 46 women) participated in the first part of this investigation. Each cyclist performed a minimum of one maximal test during which Wmax and VO2max were determined. For the second part of the study 19 cyclists completed a maximal test for the determination of Wpeak, and also a 20-km cycling time trial. Highly significant relationships were obtained between Wpeak and VO2max (r = 0.97, P less than 0.0001) and between Wpeak and 20-km cycle time (r = -0.91, P less than 0.001). Thus, Wpeak explained 94% of the variance in measured VO2max and 82% of the variability in cycle time over 20 km. We concluded that for trained cyclists, the VO2max can be accurately predicted from Wpeak, and that Wpeak is a valid predictor of 20-km cycle time.     

Anaerobic contribution to the time to exhaustion at the minimal exercise intensity at which maximal oxygen uptake occurs in elite cyclists, kayakists and swimmers

Using 23 elite male athletes (8 cyclists, 7 kayakists, and 8 swimmers), the contribution of the anaerobic energy system to the time to exhaustion (t _lim) at the minimal exercise intensity (speed or power) at which maximal oxygen uptake (V˙O_{2 max}) occurs (I _{V˙O2 max}) was assessed by analysing the relationship between the t _lim and the accumulated oxygen deficit (AOD). After 10-min warming up at 60% of V˙O_{2 max}, the exercise intensity was increased so that each subject reached his I _V˙O2max in 30 s and then continued at that level until he was exhausted. Pre-tests included a continuous incremental test with 2 min steps for determining the I _V˙O2max and a series of 5-min submaximal intensities to collect the data that would allow the estimation of the energy expenditure at I _V˙O2max . The AOD for the t _lim exercise was calculated as the difference between the above estimation and the accumulated oxygen uptake. The mean percentage value of energy expenditure covered by anaerobic metabolism was 15.2 [(SD 6)%, range 8.9–24.1] with significant differences between swimmers and kayakists (16.8% vs 11.5%, P≤0.05) and cyclists and kayakists (16.4% vs 11.5%, P≤0.05). Absolute AOD values ranged from 26.4 ml · kg⁻¹ to 83.6 ml · kg⁻¹ with a mean value of 45.9 (SD 18) ml · kg⁻¹. Considering all the subjects, the t _lim was found to have a positive and significant correlation with AOD (r = 0.62, P≤0.05), and a negative and significant correlation with V˙O_{2 max} (r = −0.46, P≤0.05). The data would suggest that the contribution of anaerobic processes during exercise performed at I _V˙O2max should not be ignored when t _lim is used as a supplementary parameter to evaluate specific adaptation of athletes. Accepted: 17 December 1996     

Effects of a low-intensity conditioning programme on V˙O2max and maximal instantaneous peak power in elderly women

The effects of 12 weeks of a low-intensity general conditioning programme on maximal instantaneous peak power (Wpeak) and maximal oxygen uptake (VO2max) were examined in 20 elderly women. After medical, familiarisation, and ethical procedures, the subjects were randomly divided into either a training and or a control group. The training group [n = 11; mean (SD) age 63.0 (3.1) years] agreed to take part in a 12-week training programme at an exercise intensity kept under 60% of the heart rate reserve for about 60 min, 3 times a week. The control group [n = 9; mean (SD) age 63.5 (3.3) years] did not perform any particular physical training. Before and after the training period, all participants underwent anthropometric measures and a maximal cycling test to exhaustion to measure their VO2max. In addition, Wpeak was determined 1 week later by the subjects performing a vertical jump from a squatting position on a force platform. Following training, neither the anthropometric characteristics nor the VO2max changed in either of the groups. In contrast, Wpeak increased significantly (P < 0.001) in the training group, but did not change in the control group. This result could be interpreted as the result of an improved level of neuromuscular activation. Furthermore, it shows that although muscle power declines with age at a faster rate than does aerobic power, its sensitivity to training seems to be higher than that of the aerobic system.     

Energy cost of front-crawl swimming in women

The purpose of this study was to examine the relationship between the energy cost of swimming per unit distance (Cs) at different velocities (v) and performance level, body size and swimming technique in women. A total of 58 females swimmers were studied. Three performance levels (A, B, C) were determined, ranging from the slower (A) to the faster (B, C). At level C and at 1.1 m.s-1, Cs,1.1 was reduced by 7% when directly compared to level B. The Cs,1.1 was reduced by 10% when calculated per unit of height (h) and by 37% when calculated per unit of h and hydrostatic lift (HL). For the whole group of swimmers, the equation regression was Cs,1.1 = 0.27 h-2.38 HL - 7.5 (r = 0.53, P less than 0.01). To evaluate the specific influence of arm length two groups of long- and short-armed swimmers were selected among swimmers of similar h and performance. The Cs was significantly higher (P less than 0.05) by 12%, SD 2.2%, for short-armed than for long-armed swimmers. To evaluate the influence of different types of swimming technique, two other groups of similar performance and anthropometric characteristics were selected. The Cs was significantly higher (P less than 0.05) by 12%, SD 4.5% for swimmers using for preference their legs rather than their arms. The Cs of the sprinters was 15.7%, SD 2% higher than that of the long-distance swimmers. For all groups, Cs increased with v on average by 8% to 11% every 0.1 m.s-1. These findings showed that Cs variations of these women were close to those previously demonstrated for men. The Cs depends on performance level, body size, buoyancy, swimming technique and v.     

Relative contribution of arms and legs in humans to propulsion in 25-m sprint front-crawl swimming

Eight male subjects were asked to swim 25 m at maximal velocity while the use of the arm(s) and legs was alternately restricted. Four situations were examined using one arm (1A), two arms (2A), one arm and two legs (1A2L) and both arms and legs (2A2L, normal swim) for propulsion. A significant mean increase of 10% on maximal velocity was obtained in 1A2L and 2A2L compared to 1A and 2A. A non-significant 4% effect was obtained in 1A. This study focused on the actual contribution of leg kick in the 10% gain in maximal velocity. It was clear that the underwater trajectory of the wrist was modified by the action of the legs (most comparisons P < 0.001). Therefore it was thought that the legs enhanced the generated propulsive force by improving the propulsive action of the arm. The arm action was quantified by selecting typical phases from the filmed trajectory of the wrist, namely forward (F), downwards (D) and backwards (B). Although there was a tendency for individual changes in kinematic parameters (F, D and B) to occur with individual changes in velocity when 2A was compared to 2A2L, no relationship was found between the relative changes in F, D and B and relative changes in velocity. This was illustrated by describing the responses of three individuals who could represent three patterns of contribution by legs and arms to propulsion in high speed swimming.     

Assessment of middle-distance running performance in sub-elite young runners using energy cost of running

The purpose of this study was to assess the validity of v _amax as an indicator of middle-distance running performance in sub-elite young runners, _amax being defined as the quotient maximal oxygen uptake (V˙O _2max) divided by the net energy cost of running (C _r) on a treadmill at a submaximal running velocity (280 m · min⁻¹). The V˙O _2max, ventilatory threshold, _amax, and C _r were assessed in 39 young male sub-elite runners having only small variations in performance level. The relationship between each variable and running performance (at 1500 m, 3000 m, and 5000 m) was evaluated. A trend toward a negative correlation existed between C _r and performance although this was not significant. The V˙O _2max and _amax were significantly related to performance. The _amax accounted for around 50% of the variability in performance whereas other physiological variables selected in this study were responsible, at best, for approximately 39%. The results presented in this study suggested that _amax was a useful indicator of middle-distance running performance in sub-elite young runners with similar performance levels as well as in top elite athletes. Accepted: 19 August 1997     

Assessment of running velocity at maximal oxygen uptake

The purpose of the study was to compare the cardiovascular, respiratory and metabolic responses to exercise of highly endurance trained subjects after 3 different nights i.e. a baseline night, a partial sleep deprivation of 3 h in the middle of the night and a 0.25-mg triazolam-induced sleep. Sleep-waking chronobiology and endurance performance capacity were taken into account in the choice of the subjects. Seven subjects exercised on a cycle ergometer for a 10-min warm-up, then for 20 min at a steady exercise intensity (equal to the intensity corresponding to 75% of the predetermined maximal oxygen consumption) followed by an increased intensity until exhaustion. The night with 3 h sleep loss was accompanied by a greater number of periods of wakefulness (P less than 0.01) and fewer periods of stage 2 sleep (P less than 0.05) compared with the results recorded during the baseline night. Triazolam-induced sleep led to an increase in stage 2 sleep (P less than 0.05), a decrease in wakefulness (P less than 0.05) and in stage 3 sleep (P less than 0.05). After partial sleep deprivation, there were statistically significant increases in heart rate (P less than 0.05) and ventilation (P less than 0.05) at submaximal exercise compared with results obtained after the baseline night. Both variables were also significantly enhanced at maximal exercise, while the peak oxygen consumption (VO2) dropped (P less than 0.05) even though the maximal sustained exercise intensity was not different.(ABSTRACT TRUNCATED AT 250 WORDS)     

Center of mass motion in swimming fish: effects of speed and locomotor mode during undulatory propulsion

Studies of center of mass (COM) motion are fundamental to understanding the dynamics of animal movement, and have been carried out extensively for terrestrial and aerial locomotion. But despite a large amount of literature describing different body movement patterns in fishes, analyses of how the center of mass moves during undulatory propulsion are not available. These data would be valuable for understanding the dynamics of different body movement patterns and the effect of differing body shapes on locomotor force production. In the present study, we analyzed the magnitude and frequency components of COM motion in three dimensions (x: surge, y: sway, z: heave) in three fish species (eel, bluegill sunfish, and clown knifefish) swimming with four locomotor modes at three speeds using high-speed video, and used an image cross-correlation technique to estimate COM motion, thus enabling untethered and unrestrained locomotion. Anguilliform swimming by eels shows reduced COM surge oscillation magnitude relative to carangiform swimming, but not compared to knifefish using a gymnotiform locomotor style. Labriform swimming (bluegill at 0.5 body lengths/s) displays reduced COM sway oscillation relative to swimming in a carangiform style at higher speeds. Oscillation frequency of the COM in the surge direction occurs at twice the tail beat frequency for carangiform and anguilliform swimming, but at the same frequency as the tail beat for gymnotiform locomotion in clown knifefish. Scaling analysis of COM heave oscillation for terrestrial locomotion suggests that COM heave motion scales with positive allometry, and that fish have relatively low COM oscillations for their body size.     

The timing of the electromyogram in the lateral myotomes of mackerel and saithe at different swimming speeds

Electromyogram (EMG) signals from two points at about 40% L and 65% L ( L = length) in the left latera1 muscle of mackerel ( Scomber scombrus L.) L = 28–33 cm a nd saithe ( Pollachius virens L.) L = 42–50 cm were recorded synchronously with films of steady straight swimming motions. In both species, the duration of EMG activity at both electrodes, remains a constant proportion of the tail cycle period Tat all the tail beat frequencies between 1–8 and 13 Hz. In mackerel and saithe respectively: onset of EMG activity at the front was 74% T and 77% T before the left-most tail blade position and fronl EMG-onset occurred 15% T and 18% T before rear onset. The duration of the EMG burst is longer at the front position (41% T and 47% T ) than at the rear (25% T and 27% T ), At all swimming speeds the wave of electrical activation of the muscle travelled between the two electrodes 25% L apart at a velocity between 1.5 and 1.6 L T ⁻¹. Frequencies of spikes within the burst of EMG activity rose from 30–40 Hz at 2 T s⁻¹ to 50–80 Hz at 8 T s⁻¹. In muscle at 40%L EMG-onset happens at phase 30° just after muscle strain at this point reaches its resting length while lengthening (360°). At 65% L EMG-onset occurs earlier in the strain cycle-350° just before the muscle reaches it resting length while lengthening (360°). This could represent within the length of the fish, a phase shift of up to 90° in the EMG-onset in relation to the muscle strain cycle. These timings are discussed in relation to optimized work output and a single instant of maximum bending moment all along the left side of the body.     

Energetics of under-water swimming in Adélie penguins (Pygoscelis adeliae)

Summary The energy consumption of Adélie penguins while at rest in water (8.4 W·kg^-1 at 4°C) or swimming below the surface was determined using a 21 m long canal fitted with respiration chambers at each end. Penguins chose to swim 86% of the time at speeds recorded in nature. Cost of transport was lowest (7.9 J·kg^-1·m^-1) at 1.7–2.3 m·s^-1, corresponding to a power input of 15.8 W·kg^-1, and only 50% as high as previously reported. Assuming a muscle efficiency of 0.25, propulsion efficiency is 0.4 and overall efficiency is 0.1. Calculated food requirements vary between 1060 g krill per adult and foraging trip at the beginning of the breeding season and 2500 g at the period of highest demand, prior to crèching of the chicks.Abbreviations BMR basal metabolic rate - COT cost of transport - DEE daily energy expenditure - DF daily food - M mass - P _i power input - P _o power output - PVC polyvinyl chloride - RMR resting metabolic rate - SE standard error - STPD Standard temperature, pressure and density - VO₂ oxygen consumption - t time     

Optimal pedalling velocity characteristics during maximal and submaximal cycling in humans

The aim of this study was to compare optimal pedalling velocities during maximal (OVM) and submaximal (OVSM) cycling in human, subjects with different training backgrounds. A group of 22 subjects [6 explosive (EX), 6 endurance (EN) and 10 non-specialised subjects] sprint cycled on a friction-loaded ergometer four maximal sprints lasting 6 s each followed by five 3-min periods of steady-state cycling at 150 W with pedalling frequencies varying from 40 to 120 rpm. The OVM and OVSM were defined as the velocities corresponding to the maximal power production and the lowest oxygen consumption, respectively. A significant linear relationship (r2 = 0.52, P < 0.001) was found between individual OVM [mean 123.1 (SD 11.2) rpm] and OVSM [mean 57.0 (SD 4.9) rpm, P < 0.001] values, suggesting that the same functional properties of leg extensor muscles influence both OVM and OVSM. Since EX was greater than EN in both OVM and OVSM (134.3 compared to 110.9 rpm and 60.8 compared to 54.0 rpm, P < 0.01 and P < 0.05, respectively) it could be hypothesised that the distribution of muscle fibre type plays an important role in optimising both maximal and submaximal cycling performance.     

Measurements of aerobic metabolism of a school of horse mackerel at different swimming speeds

Oxygen consumption rates were measured in a school of 56 horse mackerel Trachurus trachurus while at rest and while swimming at steady sustained speeds. Resting values of 38.76 and 42.10mg O₂ kg^?1 h^?1 were measured in a sealed cylindrical tank (535 l) while observing that the fish school remained neutrally buoyant and inactive with only gentle pectoral fin movements and no swimming motion. The same school was trained to swim with projected light patterns within a 10-m diameter annular doughnut respirometer. The oxygen consumption increased from the resting level through 51 mg O₂ kg^?1 h^?1 at the slowest swimming speeds of 0.29 m s^?1 (0.95 L s^?1) to around 259 mg O₂ kg^?1 h^?1 at the higher measured swimming speed of 0.87 m s^?1 (2.82 L s^?1). The data fitted a curve where oxygen consumption rose in proportion to velocity to the power of 2.56 with the intercept at the resting level. The maximum sustained speed (80 min) of 1.12 m s^?1 (3.63 Ls^?1) was not achieved within the respirometer but corresponded to an estimated oxygen consumption of 458.33 mg O₂ kg^?1 h^?1 giving a scope for aerobic activity of 419.02 mg O₂ kg^?1 h^?1. At a speed of 0.87 m s^?1, there was a lower bound on the aerobic efficiency of at least 38% and at 1.12 m s^?1, the highest aerobic speed, of 40%. Sustained speeds swum in a curved path as here should be increased by 5% for a straight path giving a maximum sustained 80 min speed of 1.18 m s^?1.