Changes in muscle strength and speed of an unloaded movement after various training programmes

Summary The effect of three different training programmes on the maximal speed of an unloaded movement (a karate punch) was studied. Three movement variables were selected: maximal speed of the hand (_h,max), maximal speed of the shoulder (_s,max) and elbow extension speed simultaneous with _h,max. The programmes were: training group 1 (TG 1,n = 8) -karate students, dynamic heavy progressive resistance exercise (incline situp and incline bench press) + punch bag exercise; training group 2 (TG 2,n = 8) - karate students, punch bag training; training group 3 (TG 3,n = 5) - no karate experience, dynamic heavy progressive resistance exercise (as in TG 1). The movement variables were calculated from chrono-cyclo photographic recordings of the punches (100 Hz). The level of significance was set at 5%. Sixteen weeks of training gave the following results: significant increases in dynamic strength in all the training groups (14%–53%). In TG 1 the _{h, max} increased significantly from 8.49 m·s^–1, SD 1.19 to 9.35 m·s^–1, SD 1.29 (10%); _s,max increased significantly in TG 1 by 32% (2.18 m·s^–1, SD 0.56 to 2.87 m·s^–1, SD 0.98) and in TG 2 by 14% (2.40 m·s^–1, SD 0.61 to 2.74 m·s^–1, SD 0.52), and in TG 3 at _{h, max} increased significantly from 28.6 rad · s^–1, SD 4.3 to 32.2 rad·s^–1, SD 4.5 (13%). No significant relationships between the changes in maximal muscle strength and the changes in movement speed were found. The significant changes in _h and _s among the karate trained subjects (TG 1 and TG 2) are ascribed to a change in the kinematics of the segmental motions induced by the karate training, to a movement pattern that takes advantage of the potentiating effect of a stretch-shortening cycle on muscle power output in flexor muscles of the shoulder and the extensor muscles of the elbow.     

Energy cost of front-crawl swimming in women

Summary The purpose of this study was to examine the relationship between the energy cost of swimming per unit distance (C_S) at different velocities () 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, C_s,1.1 was reduced by 7% when directly compared to level B. The C_s,1.1 was reduced by 10% when calculated per unit of height (h) and by 37% when calculated per unit ofh and hydrostatic lift (HL). For the whole group of swimmers, the equation regression was C_{s, 1.1} = 0.27h –2.38 HL–7.5 (r=0.53,P<0.01). To evaluate the specific influence of arm length two groups of long- and short-armed swimmers were selected among swimmers of similarh and performance. The C_s was significantly higher (P<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 C_s was significantly higher (P<0.05) by 12%, SD 4.5% for swimmers using for preference their legs rather than their arms. The C_s of the sprinters was 15.7%, SD 2% higher than that of the long-distance swimmers. For all groups, CS increased withv on average by 8% to 11% every 0.1 m · s^–1. These findings showed that C_s variations of these women were close to those previously demonstrated for men. The C_s depends on performance level, body size, buoyancy, swimming technique and .     

Relationships between postcompetition blood lactate concentration and average running velocity over 100-m and 200-m races

The relationships between anaerobic glycolysis and average velocity () sustained during sprint running were studied in 12 national level male sprinters. A blood sample was obtained within 3 min of the completion of semi-finals and finals in the 100-m and 200-m Cameroon national championships and blood lactate concentration ([la^–]_b) was measured. The 35-m times were video-recorded. The 100-m and 200-m [la^–]_b were 8.5 (SD 0.8) and 10.3 (SD 0.8) mmol·l^–1, respectively. These were not correlated with the performances. Over 200 m [la^–]_b was correlated with the sustained over the last 165 m (r=0.65,P<0.05). In the 9 athletes who participated in both the 100-m and 200-m races, the difference between the [la^–]_b measured at the end of the two races was negatively correlated to the difference in v sustained over the two races (r=0.76,P>0.02). Energy expenditure during sprint running was estimated from the [la^–]_b values. This estimate was mainly based on the assumption that a 1 mmol·l^–1 increase in [la^–]_b corresponds to the energy produced by the utilization of 3.30 ml O₂·kg^–1. The energy cost of running was estimated at 0.275 (SD 0.02) ml O₂·kg^–1·m^–1 over 200-m and 0.433 (SD 0.03) ml O₂·kg^–1·m^–1 over 100-m races. These results would suggest that at the velocities studied anaerobic glycolysis contributes to at least 55% of the energy expenditure related to sprint running. However, the influence of both mechanical factors and the contribution of other energy processes obscure the relationship between [la^–]_b and performance.     

The energy cost of walking or running on sand

Summary Oxygen uptake ( O₂) at steady state, heart rate and perceived exertion were determined on nine subjects (six men and three women) while walking (3–7 km · h^–1) or running (7–14 km · h^–1) on sand or on a firm surface. The women performed the walking tests only. The energy cost of locomotion per unit of distance (C) was then calculated from the ratio of O₂ to speed and expressed in J · kg^–1 · m^–1 assuming an energy equivalent of 20.9 J · ml O₂ ^–1. At the highest speedsC was adjusted for the measured lactate contribution (which ranged from approximately 2% to approximately 11% of the total). It was found that, when walking on sand,C increased linearly with speed from 3.1 J · kg^–1 · m^–1 at 3 km · h^–1 to 5.5 J · kg^–1 · m^–1 at 7 km · h^–1, whereas on a firm surfaceC attained a minimum of 2.3 J · kg^–1 · m^–1 at 4.5 km · h^–1 being greater at lower or higher speeds. On average, when walking at speeds greater than 3 km · h^–1,C was about 1.8 times greater on sand than on compact terrain. When running on sandC was approximately independent of the speed, amounting to 5.3 J · kg^–1 · m^–1, i.e. about 1.2 times greater than on compact terrain. These findings could be attributed to a reduced recovery of potential and kinetic energy at each stride when walking on sand (approximately 45% to be compared to approximately 65% on a firm surface) and to a reduced recovery of elastic energy when running on sand.     

Cardiac output during exercise in paraplegic subjects

Summary The purpose of this study was to measure the cardiac output using the CO₂ rebreathing method during submaximal and maximal arm cranking exercise in six male paraplegic subjects with a high level of spinal cord injury (HP). They were compared with eight able bodied subjects (AB) who were not trained in arm exercise. Maximal O₂ consumption ( O_2max) was lower in HP (1.1 1·min^–1, SD 0.1; 17.5 ml·min^–·kg, SD 4) than in AB (2.5 1·min^–1, SD 0.6; 36.7 ml·min^–1·kg, SD 10.7). Maximal cardiac output was similar in the groups (HP, 141·min^–1 SD 2.6; AB, 16.81·min^–1 SD 4). The same result was obtained for maximal heart rate (f _c,max (HP, 175 beats·min^–1, SD 18; AB, 187 beats·min^–, SD 16) and the maximal stroke volume (HP, 82 ml, SD 13; AB, 91 ml, SD 27). The slopes of the relationshipf _c/ O₂ were higher in HP than AB (P<0.025) but when expressed as a % O_2max there were no differences. The results suggests a major alteration of oxygen transport capacity to active muscle mass in paraplegics due to changes in vasomotor regulation below the level of the lesion.     

Energy cost and efficiency of riding aerodynamic bicycles

Summary Traction resistance (R _t) was determined by towing two cyclists in fully dropped posture on bicycles with an aerodynamic frame with lenticular wheels (AL), an aerodynamic frame with traditional wheels (AT), or a traditional frame with lenticular wheels (TL) in calm air on a flat wooden track at constant speed (8.6–14.6 m·s^–1). Under all experimental conditions, R _t increased linearly with the square of air velocity (_a ²); r ² equal to greater than 0.89. The constant k = R _t/_a ² was about 15% lower for AL and AT (0.157 and 0.155 N·²·m^–2) than for TL bicycles (0.184 N·²·^–2). These data show firstly, that in terms of mechanical energy savings, the role of lenticular wheels is negligible and, secondly, that for TL bicycles, the value of k was essentially equal to that found by others for bicycles with a traditional frame and traditional wheels (TT). The energy cost of cycling per unit distance (C _c, J·m^–1) was also measured for AT and TT bicycles from the ratio of the O₂ consumption above resting to speed, in the speed range from 4.7 to 11.1 m·s^–1. The C _c also increased linearly with _a ², as described by: C _c = 30.8 + 0.558 _a ² and C _c = 29.6 + 0.606 _a ² for AT and TT bicycles. Thus from our study it would seem that AT bicycles are only about 5% more economical than TT at 12.5 m·s^– the economy tending to increase slightly with the speed. Assuming a rolling coefficient equal to that observed by others in similar conditions, the mechanical efficiency was about 10% lower for aerodynamic than for conventional bicycles, amounting to about 22% and 25% at a speed of 12.5 m·s^–1. From these data it was possible to calculate that the performance improvement when riding aerodynamic bicycles, all other things being equal, ought to be about 3%. This compares favourably with the increase of about 4% observed in world record speeds (over distances from 1 to 20 km) after the adoption of the new bicycles.     

Kinematic and electromyography analysis of submaximal differences running on a firm surface compared with soft, dry sand.

Kinematic and electromyography (EMG) aspects of running on a firm surface and on soft, dry sand were studied to elucidate mechanisms contributing to the higher energy cost (EC) of sand running. Eight well-trained males (mean 64.3±8.6 ml·kg^–1·min^–1) performed barefoot running trials on a firm surface (wooden floor) and on a soft, dry sand surface (track dimensions 8.8 m×60 cm; depth 13 cm) at 8 and 11 km·h^–1. Kinematic and EMG data were collected simultaneously using an integrated six-camera 50 Hz VICON motion analysis system, an AMTI force-plate and a 10-channel EMG system. Running at 8 km·h^–1 on sand resulted in a greater (P<0.05) stance time (t_s) compared with the firm surface. At 11 km·h^–1, sand running resulted in a greater stance-to-stride ratio (P<0.005), a shorter stride length (SL) (P<0.05), and a greater cadence (P<0.001) compared with the firm surface values. Hip and knee flexion at initial foot contact (IFC), mid-support (MS) and flexion maximum were greater (P<0.001) running on sand compared with firm surface values at 8 and 11 km·h^–1. Over duration of stride, Hamstring (semimembranosus and biceps femoris) EMG was greater running on sand compared with the firm surface at 8 (P<0.001) and 11 (P<0.05) km·h^–1. During the stance phase in the 8-km·h^–1 trials, EMG in the Hamstrings (P<0.001), Vastii (Vastus lateralis and Vastus Medialis) (P<0.02), Rectus femoris (Rec Fem) (P<0.01) and Tensor Fascia Latae (Tfl) (P<0.0001) were greater than the firm surface measures. During stance in the 11-km·h^–1 trials, Tfl EMG was greater (P<0.02) running on sand compared with the firm surface. At IFC and MS, Hamstrings EMG was greater on sand at both running speeds (P<0.001). For the Vastii (P<0.02), Rec Fem (P<0.0001) and Tfl (P<0.0001) muscles, the EMG at MS running on sand at both speeds was greater than the firm surface values. The increased EC of running on sand can be attributed in part to the increased EMG activation associated with greater hip and knee range of motion compared with firm surface running.     

Validity and reliability of pedometers in habitual activity research

Summary In 12–18 year old boys actual steprate on a treadmill was compared to the scores of two types of mechanical pedometers (Russian and German), attached to the waist. Both types show deviations from actual steprate in running at speeds of 8 and 10 km·h^–1 of ca. 5% (±9%). In walking or running at 6 km·h^–1 and in running at 14 km·h^–1 both types give an overestimation of ca. 8.5% (±8%). In walking at a speed of 2 and 4 km·h^–1 the scores are not reliable because of the big standard deviation of ca. 34%. Oxygen uptake (ml·kg^–1) and heart rate (beats·min^–1) increase more in running than in walking, actual steprate (steps·min^–1) however increases less in running compared to walking. If pedometers register only during running they reflect actual steprate fairly good and give a good estimation of the change in oxygen uptake as speed gathers.     

Neuromuscular characteristics and fatigue in endurance and sprint athletes during a new anaerobic power test

The purpose of this study was to investigate neuromuscular and energy performance characteristics of anaerobic power and capacity and the development of fatigue. Ten endurance and ten sprint athletes performed a new maximal anaerobic running power test (MARP), which consisted ofn x 20-s runs on a treadmill with 100-s recovery between the runs. Blood lactate concentration [la^–]_b was measured after each run to determine submaximal and maximal indices of anaerobic power (P _3mmol·1 ^–1,P_5mmol·1 ^–1,P_10mmol·1 ^–1andP _max) which was expressed as the oxygen demand of the runs according to the American College of Sports Medicine equation: the oxygen uptake (ml·kg^–1·min^–1)=0.2·velocity (m·min^–1) +0.9·slope of treadmill (frac)·velocity (m·min^–1)+3.5. The height of rise of the centre of gravity of the counter movement jumps before (CMJ_rest) and during (CMJ) the MARP test, as well as the time of force production (t _F) and electromyographic (EMG) activity of the leg muscles of CMJ performed after each run were used to describe the neuromuscular performance characteristics. The maximal oxygen uptake ( _max), anaerobic and aerobic thresholds were determined in the _max test, which consisted ofn x 3-min runs on the treadmill. In the MARP-testP _max did not differ significantly between the endurance [116 (SD 6) ml·kg^–1·min^–1] and sprint [120 (SD 4) ml·kg^–1·min^–1] groups, even though CMJ_rest and peak [la^–]_b were significantly higher and _max was significantly lower in the sprint group than in the endurance group and CMJ_rest height correlated withP _max (r=0.50,P<0.05). The endurance athletes had significantly higher mean values ofP _3mmol·1 ^–1andP _5mmol·1 ^–1[89 (SD 7) vs 76 (SD 8) ml·kg^–1·min^–,P<0.001 and 101 (SD 5) vs 90 (SD 8) ml·kg^–1·min^–1,P<0.01. Significant positive correlations were observed between theP _3mmol·l ^–1and _max, anaerobic and aerobic thresholds. In the sprint group CMJ and the averaged integrated iEMG decreased andt _F increased significantly during the MARP test, while no significant changes occurred in the endurance group. The present findings would suggest thatP _max reflected in the main the lactacid power and capacity and to a smaller extent alactacid power and capacity. The duration of the MARP test and the large number of CMJ may have induced considerable energy and neuromuscular fatigue in the sprint athletes preventing them from producing their highest alactacidP _max at the end of the MARP test. Due to lower submaximal [la^–]_b (anaerobic sprinting economy) the endurance athletes were able to reach almost the sameP _max as the sprint athletes.     

Estimation of<Emphasis Type="Italic"> V̇</Emphasis>O<Subscript>2max</Subscript> from the ratio between HR<Subscript>max </Subscript>and HR<Subscript>rest</Subscript> – the Heart Rate Ratio Method

The effects of ̇raining and/or ageing upon maximal oxygen uptake (O_2max) and heart rate values at rest (HR_rest) and maximal exercise (HR_max), respectively, suggest a relationship between O_2max and the HR_max-to-HR_rest ratio which may be of use for indirect testing of O_2max. Fick principle calculations supplemented by literature data on maximum-to-rest ratios for stroke volume and the arterio-venous O₂ difference suggest that the conversion factor between mass-specific O_2max (ml·min^–1·kg^–1) and HR_max·HR_rest ^–1 is ~15. In the study we experimentally examined this relationship and evaluated its potential for prediction of O_2max. O_2max was measured in 46 well-trained men (age 21–51 years) during a treadmill protocol. A subgroup (n=10) demonstrated that the proportionality factor between HR_max·HR_rest ^–1 and mass-specific O_2max was 15.3 (0.7) ml·min^–1·kg^–1. Using this value, O_2max in the remaining 36 individuals could be estimated with an SEE of 0.21 l·min^–1 or 2.7 ml·min^–1·kg^–1 (~4.5%). This compares favourably with other common indirect tests. When replacing measured HR_max with an age-predicted one, SEE was 0.37 l·min^–1 and 4.7 ml·min^–1·kg^–1 (~7.8%), which is still comparable with other indirect tests. We conclude that the HR_max-to-HR_rest ratio may provide a tool for estimation of O_2max in well-trained men. The applicability of the test principle in relation to other groups will have to await direct validation. O_2max can be estimated indirectly from the measured HR_max-to-HR_rest ratio with an accuracy that compares favourably with that of other common indirect tests. The results also suggest that the test may be of use for O_2max estimation based on resting measurements alone.An erratum to this article can be found at     

Effects of age and physical performance capacity on distribution and composition of high-density lipoprotein subfractions in men

Summary The influences of age and maximal aerobic capacity ( ) on serum lipoproteins with special regard to the concentration, composition and distribution of high density lipoprotein (HDL) subfractions were investigated in 51 healthy males of different characteristics: younger than 35 years, untrained (n = 14, mean age 28.2 years, SD 6.0; , 47.9 ml·kg^–1 min^–1, SD 5.8) and trained (n = 11, mean age 27.9 years, SD 4.3; , 61.1 ml·kg^–1·min^–1, SD 5.1), older than 50 years untrained (n = 14, mean age 58.9 years, SD 5.9, , 29.3 ml·kg^–1 · min^–1, SD 5.3) and trained (n = 12, mean age 59.3 years, SD 7.2, , 45.7 ml·kg^–1 · min^–, SD 7.7). The fasting-state serum concentrations of total cholesterol, tri-acylglycerol and lipoprotein-cholesterol were measured. The HDL-subfractions were separated by density () gradient ultracentrifugation. Concentrations of cholesterol, cholesterylester, tri-acylglycerol, phospholipids, apolipoprotein (apo) A-I and A-II were measured in the subfractions HDI_2b: = 1.063–1.100 g·ml^–1; HDL_2a: = 1.001–1.110 g · ml^–1; HDL_2a2: = 1.110-1.150 g · ml^–1; HDL₃ = 1.150–1.210 g · ml^–1. Elderly untrained subjects showed increased serum concentrations of total-, very low- and low density lipoprotein-cholesterol and elevated tri-acylglycerol levels. The HDL-cholesterol concentration was decreased, due to reduced concentrations of HDL₂-subfractions. Significant changes in the composition of HDL₂-subfractions were found in elderly untrained subjects. The HDL₂-subfractions had more protein, a decreased apoA-I:A-II ratio and less phospholipids in comparison to HDL₂-subfractions from younger untrained and trained, and elderly trained subjects. The results indicate a modified HDL-metabolism within the elderly untrained subjects. The fact that the elderly trained, in contrast to the elderly untrained subjects did not show any changes in HDL-metabolism compared to the younger groups suggests that physical activity may be an important factor in influencing HDL-metabolism, especially in subjects of advanced age.     

The energy cost of running increases with the distance covered

Summary The net energy cost of running per unit of body mass and distance (C_r, ml O₂·kg^–1·km^–1) was determined on ten amateur runners before and immediately after running 15, 32 or 42 km on an indoor track at a constant speed. The C_r was determined on a treadmill at the same speed and each run was performed twice. The average value of C_r, as determined before the runs, amounted to 174.9 ml O₂·kg^–1·km^–1 SD 13.7. After 15 km, C_r was not significantly different, whereas it had increased significantly after 32 or 42 km, the increase ranging from 0.20 to 0.31 ml O₂·kg^–1·km^–1 per km of distance (D). However, C_r before the runs decreased, albeit at a progressively smaller rate, with the number of trials (N), indicating an habituation effect (H) to treadmill running. The effects of D alone were determined assuming that C_r increased linearly with D, whereas H decreased exponentially with increasing N, i.e.C _r =C _r0+aD+He^–bN. The C_ro, the true energy cost of running in nonfatigued subjects accustomed to treadmill running, was assumed to be equal to the average value of C_r before the run for N equal to or greater than 7 (171.1 ml O₂·kg^–1·km^–1, SD 12.7;n = 30). A multiple regression of C_r on N and D in the form of the above equation showed firstly that Cr increased with the D covered by 0.123%·km^–1, SEM 0.006 (i.e. about 0.22 ml O₂·kg^–1·km^–1 per km,P<0.001); secondly, that in terms of energy consumption (obtained from oxygen consumption and the respiratory quotient), the increase of C_r with D was smaller, amounting on average to 0.08%·km^–1 (0.0029 J·kg^–1·m^–1,P<0.001) and thirdly that the effects of H amounted to about 16% of C_r0 for the first trial and became negligible after three to four trials.     

Comparison of haemodynamic effects during venous air infusion and after decompression in pigs

We have compared haemodynamic effects of venous gas emboli during continuous air infusion into the right atrium and after rapid decompression in pigs. Eight anaesthetized and spontaneously breathing pigs received continuous air infusion at a rate of either 0.05 ml·kg^–1 · min^–1 (six pigs, air infusion group) or 0.10 ml·kg^–1 · min^–1 (two pigs). Another eight pigs (decompression group) underwent a 30-min compression to 5 bar (500 kPa, absolute pressure), followed by a rapid decompression (2 bar·min^–1). Haemodynamic variables were measured or calculated, and bubbles in the pulmonary artery were monitored using transoesophageal echocardiography. The results showed less variation in the maximal increase in mean pulmonary arterial pressure ( _{a, pulm}) during air infusion (0.05 ml·kg^–1 · min^–1) than after decompression, although the mean maximal increase did not differ between the two groups [28.0 mmHg (3.73 kPa), 95% confidence interval (CI) 23.5–32.5, vs 32.0 mmHg (4.27 kPa), 95% CI 25.3-38.7, P=0.3]. The _a,pulm stabilized or decreased very slowly after peak values were reached in the air infusion group, whereas the _a,pulm decreased rapidly during the same period in the decompression group. No significant changes in mean arterial pressure were observed during air infusion (0.05 ml· kg^–1 · min^–1), in contrast to the rapid increase and the subsequent decrease, that appeared after decompression. Finally, the maximal bubble count was much lower in the air infusion group than in most of the pigs in the decompression group. The two pigs that received 0.10 ml·kg^–1 · min^–1 stopped breathing after 5-min infusion, developed arterial hypotension and died.     

Energy cost and efficiency of sculling a Venetian gondola

Summary Oxygen uptake was measured on four male subjects during sculling gondolas at constant speeds from 1 to 3 m · s^–1. The number of scullers on board in the different trials was one, two or four. Tractional water resistance (drag,D, N) was also measured in the same range of speeds. Energy cost of locomotion per unit of distance (C, J·m^–1), as calculated from the ratio of O₂ uptake above resting to, increased with v according to a power function (C=155.2· ^1.67;r=0.88). AlsoD could be described as a power function of the speed:D=12.3· ^2.21;r= 0.94). The overall efficiency of motion, as obtained from the ratio ofD toC increased with speed from 9.2% at 1.41 m· s^–1 to 14.5% at 3.08 m·s^–1. It is concluded that, in spite of this relatively low efficiency of motion, the gondola is a very economic means. Indeed, at low speeds ( 1 m·s^–1), the absolute amount of energy for propelling a gondola is the same as that for waking on the level at the same speed for a subject of 70 kg body mass.     

Sweat lactate response between males with high and low aerobic fitness

Sweat lactate indirectly reflects eccrine gland metabolism. However the potential influence of aerobic fitness on sweat lactate is not well-understood. Six males with high aerobic fitness [peak oxygen consumption (O₂peak): 61.6 (2.5) ml·kg^–1·min^–1] and seven males with low aerobic fitness [O₂peak: 41.8 (6.4) ml·kg^–1·min^–1] completed a maximal exertion cycling trial followed on a different day by 60 min of cycling (60 rev·min^–1) in a 30°C wet bulb globe temperature environment. Intensity was individualized at 90% of the ventilatory threshold ( _E/O₂ increase with no concurrent _E/CO₂ increase). Sweat samples were collected from the lumbar region every 10 min and analyzed for lactate concentration. Sweat rate (SR) was significantly greater (p<0.05) for subjects with a high [1445 (254) ml·h^–1] versus a low [1056 (261) ml·h^–1] fitness level. Also, estimated total lactate excretion (SR×mean sweat lactate concentration) was marginally greater (p=0.2) in highly fit males. However, repeated measures ANOVA showed no significant differences (p>0.05) between groups for sweat lactate concentration at any time point. Current results show highly fit (vs. low fitness level) males have a greater sweat rate which is consistent with previous literature. However aerobic fitness and subsequent variations in SR do not appear to influence sweat lactate concentrations in males.     

Endurance training slows down the kinetics of heart rate increase in the transition from moderate to heavier submaximal exercise intensities

Summary To find out whether endurance training influences the kinetics of the increases in heart rate (f _c) during exercise driven by the sympathetic nervous system, the changes in the rate off _c adjustment to step increments in exercise intensities from 100 to 150 W were followed in seven healthy, previously sedentary men, subjected to 10-week training. The training programme consisted of 30-min cycle exercise at 50%–70% of maximal oxygen uptake ( O_2max) three times a week. Every week during the first 5 weeks of training, and then after the 10th week the subjects underwent the submaximal three-stage exercise test (50, 100 and 150 W) with continuousf _c recording. At the completion of the training programme, the subjects' O_2max had increased significantly(39.2 ml·min^–1·kg^–1, SD 4.7 vs 46 ml·min^–1·kg^–1, SD 5.6) and the steady-statef _c at rest and at all submaximal intensities were significantly reduced. The greatest decrease in steady-statef _c was found at 150 W (146 beats·min^–1, SD 10 vs 169 beats·min^–1, SD 9) but the difference between the steady-statef _c at 150 W and that at 100 W (f _c) did not decrease significantly (26 beats·min^–1, SD 7 vs 32 beats·min^–1, SD 6). The time constant () of thef _c increase from the steady-state at 100 W to steady-state at 150 W increased during training from 99.4 s, SD 6.6 to 123.7 s, SD 22.7 (P<0.01) and the acceleration index (A=0.63·f _c·^–1) decreased from 0.20 beats·min^–1·s^–1, SD 0.05 to 0.14 beats·min^–1·s^–1, SD 0.04 (P<0.02). The major part of the changes in and A occurred during the first 4 weeks of training. It was concluded that heart acceleration following incremental exercise intensities slowed down in the early phase of endurance training, most probably due to diminished sympathetic activation.     

Verification of the heart rate threshold

Among the methods for determining anaerobic threshold (AT), the heart rate (HR) method seems to be the simplest. On the other hand, many conflicting results from comparing this method with others have been presented over the last 10 years. Therefore, the aim of this study was to compare the heart rate threshold (HRT) with the lactate turn point (LTP) —second break point of dependence of lactate (LA) to power output, ventilatory threshold (VT) and threshold determined by electromyography (EMG_AT), all determined by the same exercise test and evaluated by the same computer algorithm. A group of 24 female students [mean age 20.5 (SD 1.6) years, maximal oxygen consumption 48.8 (SD 4.7) ml · kg^–1 · min^–1 performed an incremental exercise test on a cycle ergometer (modified Conconi test) starting with an initial power output (PO) of 40 W with intensity increments of 10 W · min^–1 until the subjects were exhausted. The HRT, LTP and EMG_AT determination was done by computer-aided break-point regression analysis from dependence of functional measures on PO. The same computer algorithm was used for VT determination from the relationship between ventilation (V) and oxygen uptake ( O₂) or carbon dioxide output ( CO₂). Nonsignificant differences were found between HRT [ O₂ 35.2 (SD 4.2) ml · kg^–1 · min^–1; HR 170.8 (SD 5.5) beats min^–1; LA 4.01 (SD 1.03) mmol · l^–1; PO 2.27 (SD 0.33) W · kg^–1 VT [ O₂ 35.1 (SD 3.7) ml · kg^–1 · min^–1 HR 168.3 (SD 4.8) beats · min^–1; LA 3.87 (SD 1:17) mmol · l^–1; PO 2.22 (SD 0.27) W · kg^–1 EMG_AT [ O₂35.6 (SD 4.1) ml · kg^–1 · min^–1 HR 171.0 (SD 5.4) beats · min^–1; LA 4.11 (SD 0.98) mmol · l^–1; PO 2.30 (SD 0.31) W · kg^–1] and LTP [ O₂) 35.3 (SD 4.1) ml · kg^–1 · min^–1; HR 170.1 (SD 6.0) beats · min^–1; LA 3.99 (SD 0.76) mmol · l^–1; PO 2.27 (SD 0.29) W · kg^–1]. Highly significant correlations (P < 0.01 in all cases) were found among all measurements made at threshold level in all the thresholds investigated. Correlation coefficients ranged in selected variables at different threshold levels from 0.842 to 0.872 in O₂ measured in ml · kg^–1 · min^–1, from 0.784 to 0.912 for LA, from 0.648 to 0.857 for HR, and from 0.895 to 0.936 for PO measured in W · kg^–1. These findings have led us to conclude that HRT could be used as an alternative method of determining anaerobic threshold in untrained subjects.     

Effect of endurance training on excessive CO2 expiration due to lactate production in exercise

Summary We attempted to determine the change in total excess volume of CO₂ Output (CO₂ excess) due to bicarbonate buffering of lactic acid produced in exercise due to endurance training for approximately 2 months and to assess the relationship between the changes of CO₂ excess and distance-running performance. Six male endurance runners, aged 19–22 years, were subjects. Maximal oxygen uptake (VO_2max), oxygen uptake (VO₂) at anaerobic threshold (AT), CO₂ excess and blood lactate concentration were measured during incremental exercise on a cycle ergometer and 12-min exhausting running performance (12-min ERP) was also measured on the track before and after endurance training. The absolute magnitudes in the improvement due to training for C02 excess per unit of body mass per unit of blood lactate accumulation (Ala^–) in exercise (CO₂ excess·mass^–1·la^–), 12-min ERP, VO₂ at AT (AT-VO₂) and VO_2max on average were 0.8 ml·kg^–1·l^–1·mmol^–1, 97.8m, 4.4 ml·kg^–1· min^–1 and 7.3 ml·kg^–1·min^–1, respectively. The percentage change in CO₂ excess·mass^–1·la^– (15.7%) was almost same as those of VO_2max (13.7%) and AT-VO₂ (13.2%). It was found to be a high correlation between the absolute amount of change in CO₂ excess·mass^–1·la^– and the absolute amount of change in AT-VO₂ (r=0.94, P<0.01). Furthermore, the absolute amount of change in C02 excess·mass^–1·la^–, as well as that in AT-VO₂ (r=0.92, P<0.01), was significantly related to the absolute amount of change in 12-min ERP (r=0.81, P<0.05). It was concluded that a large CO₂ excess·mass^–1·la^–1 of endurance runners could be an important factor for success in performance related to comparatively intense endurance exercise such as 3000–4000 m races.     

Comparison of treadmill exercise testing protocols for wheelchair users

Summary The reduced early mortality and the increased life span of persons with spinal cord injury (SCI) and other chronically disabling conditions which result in loss of use of the legs places them at increased risk of coronary heart disease, diabetes, and hypertension. Exercise testing in this population is becoming more common, but there is a need for assessment of protocols in order to determine the best method to elicita maximal response in a reasonable time without endangering the patient. Three wheelchair treadmill protocols were compared in seven men with paraplegia aged 21–44 years (five SCI, two post-polio). Subjects repeated each protocol to estimate reliability. Protocol G consisted of increasing treadmill grade at a constant speed (4.8 km·h^–1); in protocol S, the speed was increased at a constant grade (0%), and in protocol C, speed and grade were increased. Two-minute stages were used in all protocols. Peak oxygen uptake [ O_2max; mean (SD): 23.6 (5.8) ml·kg^–1·min^–1; 1.66 (0.37) l·min^–1], CO₂ production [1.98 (0.46) l·min^–1], ventilation volume [83.0 (25.6) l·min^–1], respiratory exchange ratio [1.2 (0.12)], and heart rate [173 (18)] were determined. Over all trials none of the variables was significantly different among the three protocols, but all were highest in C and lowest in S. Reliability coefficients for absolute and relative O_2max ranged from 0.76 and 0.81 in G to 0.95 and 0.98 in C (all P<0.05). These data suggest that an incremental treadmill test similar to the C protocol may be the optimal method to use when evaluating the exercise capacity of wheelchair users.     

Influence of acute maximal exercise on lecithin: cholesterol acyltransferase activity in healthy adults of differing aerobic performance

Summary To document the possible influence of a single episode of maximal aerobic stress on the serum lecithin: cholesterol acyltransferase (LCAT) activity in subjects with differing histories of training, two groups of healthy male adults [controls (C),n = 18, 28.6 years, SD 5.2, 50.1 ml · kg^–1 · min^–1 maximal O₂ uptake (VO_2max), SD 5.3; endurance trained athletes (T),n = 18, 31.4 years, SD 8.8, 65.0 ml · kg^–1 · min^–1 VO_2max, SD 2.8] were examined in a maximal aerobic stress test. In addition to the routine assessment of lipid status, LCAT activity was measured immediately before and after exercise. At rest nearly identical LCAT activity values were found in both groups: C 64.4 nmol · ml^–1 · h^–1, SD 16.7 vs T 65.0 nmol · ml^–1 · h^–1, SD 20.9. The post-exercise LCAT values induced by the maximal stress test increased significantly to (C) 95.7 nmol · ml^–1 · h^–1, SD 23.5, +48.6%,P<0.001; (T) 83.5 nmol · ml^–1 · h^–1, SD 24.3, +29.1%,P<0.01. Neither the pre nor the post-exercise individual LCAT activity values showed any significant correlation to the corresponding data on physical performance.