Effect of previous supramaximal work on lacticaemia during supra-anaerobic threshold exercise

Summary Twelve male and female subjects (eight trained, four untrained) exercised for 30 min on a treadmill at an intensity of maximal O₂ consumption (% O_2max) 90.0%, SD 4.7 greater than the anaerobic threshold of 4 mmol ·1^–1 (Th_an =83.6% O_2max, SD 8.9). Time-dependent changes in blood lactate concentration ([la_b]) during exercise occurred in two phases: the oxygen uptake ( O₂) transient phase (from 0 to 4 min) and the O₂ steady-state phase (4–30 min). During the transient phase, [la_b] increased markedly (l.30 mmol · l ^–1 · min ^–1, SD 0.13). During the steady-state phase, [la_b] increased slightly (0.02 mmol · 1^–1 · min^–1, SD 0.06) and when individual values were considered, it was seen that there were no time-dependent increases in [la_b] in half of the subjects. Following hyperlacticaemia (8.8 mmol -l^–1, SD 2.0) induced by a previous 2 min of supramaximal exercise (120% O_2max), [la_b] decreased during the O₂ transient (–0.118 mmol · 1^–1 · min^–1, SD 0.209) and steady-state (–0.088 mmol · 1^–1 · min ^–1, SD 0.103) phases of 30 min exercise (91.4% O_2max, SD 4.8). In conclusion, it was not possible from the Th_an to determine the maximal [la_b] steady state for each subject. In addition, lactate accumulated during previous supramaximal exercise was eliminated during the O₂ transient phase of exercise performed at an intensity above the Th_an. This effect is probably largely explained by the reduction in oxygen deficit during the transient phase. Under these conditions, the time-course of changes in [la_b] during the O₂ steady state was also affected.     

Dissociation between\dot V_{O_2 \max } and ventilatory threshold responses to endurance training

Summary The purpose of this investigation was to determine whether the ventilatory gas exchange threshold (T_vent) changes significantly during the first 1–3 weeks of endurance training. Six men were studied during 3 weeks of training, which consisted of pedaling on a cycle ergometer 6 d·wk 30 min per session at 70% of pretraining . At the end of each week, T_vent, and maximal and submaximal heart rates were determined during an incremental exercise test on the cycle ergometer. Constant-load submaximal exercise blood lactate concentrations were determined during training sessions on Monday, Wednesday, and Friday of each week of training. T_vent did not change significantly during the 3 weeks of training (+ 0.09 l·min^–1;P>0.05). In contrast, significant changes occurred in all other training indexes measured. increased by 0.36 l·min^–1 (P<0.05) after just 2 weeks of training and did not change further after 3 weeks. Significant reductions (40–45%;p<0.05) in blood lactate levels during training sessions occurred by the middle of the 2nd week of training. Decreases in maximal (~ 11 bt·min^–1) and submaximal (~ 14 bt·min^–1) exercise heart rates after 1 week of training were significant (P<0.05). The results demonstrate that changes in T_vent lag behind alterations in several other cardiovascular and metabolic parameters in response to endurance training. The dissociation between the significant improvement in and the lack of a significant increase in T_vent during the first 3 weeks of training indicates that the exercise-induced changes in these two parameters are regulated by different mechanisms.     

Comparison of mathematically determined blood lactate and heart rate “threshold” points and relationship with performance

Summary The purpose of this study was to investigate the relationship between threshold points for heart rate ( ) and blood lactate (Th_1a) as determined by two objective mathematical models. The models used were the mono-segmental exponential (EXP) model of Hughson et al. and the log-log (LOG) model of Beaver et al. Inter-correlations of these threshold points and correlations with performance were also studied. Seventeen elite runners (mean, SD = 27.5, 6.5 years; 1.73, 0.05 m; 63.8, 7.3 kg; and maximum oxygen consumption of 67.8, 3.7 ml · kg^–1 · min^–1) performed two maximal multistage running field tests on a 183.9-m indoor track with inclined turns. The initial speed of 9 km · h^–1 (2.5 m · s^–1) was increased by 0.5 km · h^–1 (0.14 m · s^–1) every lap for thef _c test and by 1 km · h^–1 (0.28 m · s^–1) every 4 min for the la test. After fitting the la or thef _c data to the two mathematical models, the threshold speed was assessed in the LOG model from the intersection of the two linear segments (LOG-1a; LOG-f _c) and in the EXP model from a tangent point (TI-1a; TI-f _c). Th_1a and speeds computed with the two models were significantly different (P<0.001) and poorly correlated (LOG-1a vs LOG-f _c:r=0.36, TI-1a vs TI-f _c:r=0.13). In general, were less well correlated with performance than Th_1a. With two different objective mathematical models, this study has shown significant differences and poor correlations between Th_1a and . Thus thef _c inflection point with Conconi's protocol is a poor indicator of the la breakpoint with a conventional multistage protocol and a weaker indicator of running performance.     

Influence of training on sleeping heart rate following daytime exercise

Summary The purpose of this investigation was to examine the influence of daytime exercise on heart rate during sleep. Nine, untrained male college students volunteered to participate. They cycled at 75% maximum oxygen uptake, ( O_2max) 30 min·day^–1 for 12 weeks. The exercise duration was increased by 5 min every 4 weeks from 30 to 40 min per session. Post-training O_2max[mean (SE): 48.9 (1.7) ml · kg^–1 · min^–1] values were significantly (P<0.01) higher than pre-training [45.5 (1.8) ml-kg^–1·min^–1] values. Before and after training, sleeping heart rate was assessed on two separate nights. Data were obtained during a night following 30 min of daytime cycling at 75 (6) % O_2maxand on a night in which no daytime exercise was performed. A three-way repeated measures ANOVA [training status (pre-/post-training) × activity (exercise day/nonexercise day) × sleep time (18 epochs of 20 min each)] revealed a significant main effect for sleep time (P < 0.001) as well as a sleep time × training status interaction (P<0.02). No significant difference in sleeping heart rate was noted when exercise and non-exercise days were compared both before and after training. It is concluded that endurance training in these young adult men: (1) hastens the achievement of baseline heart rate during sleep, and (2) does not moderate the relationship between an acute bout of daytime exercise and sleeping heart rate.     

Influence of ageing on aerobic parameters determined from a ramp test

Summary The purpose of this study was to examine the four parameters of aerobic function, the maximum oxygen uptake ( O_2max), ventilation threshold (Th _VE), efficiency, and the effective time constant for oxygen consumption ( 0₂), across age. In particular, the study was designed to observe whether there may be accelerated declines in aerobic function beyond 60 years of age. Seventy-nine sedentary men aged 30–84 years were studied. Each subject performed two maximal cycle ramp function tests, and data were collected on a breath-by-breath basis. The O_2max, from a plateau in 0₂, was achieved in 87% of the subjects using the ramp test. The O_2max showed a significant decrease with increasing age (from linear regression,r = –0.81) at a rate averaging 0.037 l·min^–1·year^–1. The Th _VE also declined with increasing age, but at a slower rate (0.013 l·min^–1·year^–1). The O₂ was significantly increased across the age groups from 69 s for those aged 30–40 years to 98s for those aged 60 years or more. There was no evidence of accelerated decline in these aerobic parameters beyond age 60 years, and there were no differences in efficiency (27.5–29.9%) across age. Although other forcing functions should be used to confirm this characterization of the oxygen kinetics, this slowed response with age would result in greater oxygen deficit and possibly earlier fatigue in response to even light exercise in older individuals.     

Oxygen uptake during running as related to body mass in circumpubertal boys: a longitudinal study

Summary To investigate the effect of endurance training on physiological characteristics during circumpubertal growth, eight young runners (mean starting age 12 years) were studied every 6 months for 8 years. Four other boys served as untrained controls. Oxygen uptake ( O ₂) and blood lactate concentrations were measured during submaximal and maximal treadmill running. The data were aligned with each individual's age of peak height velocity. The maximal oxygen uptake ( O _2max; ml · kg^–1 · min^–1) decreased with growth in the untrained group but remained almost constant in the training group. The oxygen cost of running at 15 km · h^–1 ( O ₂₁₅, ml · kg^–1 · min^–1) was persistently lower in the trained group but decreased similarly with age in both groups. The development of O _2max and O ₂₁₅ (1 · min^–1) was related to each individual's increase in body mass so that power functions were obtained. The mean body mass scaling factor was 0.78 (SEM 0.07) and 1.01 (SEM 0.04) for O _2max and 0.75 (SEM 0.09) and 0.75 (SEM 0.02) for O ₂₁₅ in the untrained and trained groups, respectively. Therefore, expressed as ml · kg^–0.75 · min^–1, O ₂₁₅ was unchanged in both groups and O _2max increased only in the trained group. The running velocity corresponding to 4 mmol · 1^–1 of blood lactate ( _la4) increased only in the trained group. Blood lactate concentration at exhaustion remained constant in both groups over the years studied. In conclusion, recent and the present findings would suggest that changes in the oxygen cost of running and O _2max (ml · kg^–1 · min^–1) during growth may mainly be due to an overestimation of the body mass dependency of O ₀₂ during running. The O ₂ determined during treadmill running may be better related to kg^0.75 than to kg¹.     

Maximal oxygen uptake,anaerobic threshold and running economy in women and men with similar performances level in marathons

Sex differences in running economy (gross oxygen cost of running, C_R), maximal oxygen uptake (VO_2max), anaerobic threshold (Th_an), percentage utilization of aerobic power (% VO_2max), and Th_an during running were investigated. There were six men and six women aged 20–30 years with a performance time of 2 h 40 min over the marathon distance. The VO_2max, Th_an, and CR were measured during controlled running on a treadmill at 1° and 3° gradient. From each subject's recorded time of running in the marathon, the average speed (v _M) was calculated and maintained during the treadmill running for 11 min. The VO_{2 max} was inversely related to body mass (m _b), there were no sex differences, and the mean values of the reduced exponent were 0.65 for women and 0.81 for men. These results indicate that for running the unit ml·kg^–0.75·min^–1 is convenient when comparing individuals with different m _b. The VO_2max was about 10% (23 ml·kg^–0.75·min^–1) higher in the men than in the women. The women had on the average 10–12 ml·kg^–0.75·min^–1 lower VO₂ than the men when running at comparable velocities. Disregarding sex, the mean value of C_R was 0.211 (SEM 0.005) ml·kg^–1·m^–1 (resting included), and was independent of treadmill speed. No sex differences in Th_an expressed as % VO_2max or percentage maximal heart rate were found, but Than expressed as VO₂ in ml·kg^–0.75·min^–1 was significantly higher in the men compared to the women. The percentage utilization of f _emax and concentration of blood lactate at v _M was higher for the female runners. The women ran 2 days more each week than the men over the first 4 months during the half year preceding the marathon race. It was concluded that the higher VO_2max and Th_an in the men was compensated for by more running, superior C_R, and a higher exercise intensity during the race in the performance-matched female marathon runners.     

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.     

The ventilatory threshold gives maximal lactate steady state

Summary The purpose of this study was to examine whether the ventilatory threshold (Th _v) would give the maximal lactate steady state ([1a]_{ss, max}), which was defined as the highest work rate (W) attained by a subject without a progressive increase in blood lactate concentration [1a]_b at constant intensity exercise. Firstly, 8 healthy men repeated ramp-work tests (20 W·min^–1) on an electrically braked cycle ergometer on different days. During the tests, alveolar gas exchange was measured breath-by-breath, and theW atTh _v (W _{Th v}) was determined. The results of two-way ANOVA showed that the coefficient of variation of a singleW _{Th v} determination was 2.6%. Secondly, 13 men performed 30-min exercise atW _{Th v} (Th _v trial) and at 4.9% aboveW _{Th v} (Th _v + trial), which corresponded to the 95% confidence interval of the single determination. The [1a]_b was measured at 15 and 30 min from the onset of exercise. The [1a]_b at 15 min (3.15 mmol·1^–1, SEM 0.14) and at 30 min (2.95 mmol·1^–1, SEM 0.18) were not significantly different inTh _v trial. However, the [1a]_b ofTh _v+ trial significantly increased (P<0.05) from 15 min (3.62 mmol·1^–1, SEM 0.36) to 30 min (3.91 mmol·1^–1, SEM 0.40). These results indicate thatTh _v gives the [1a]_ss,max, at which one can perform sustained exercise without continuous [1a]_b accumulation.     

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.     

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.     

Bio-energetic profile in 144 boys aged from 6 to 15 years with special reference to sexual maturation

Summary The effects of growth and pubertal development on bio-energetic characteristics were studied in boys aged 6–15 years (n = 144; transverse study). Maximal oxygen consumption (VO_2max, direct method), mechanical power at (VO_2max ( ), maximal anaerobic power (P_max; force-velocity test), mean power in 30-s sprint (P _30s; Wingate test) were evaluated and the ratios between P_max,P _30s and were calculated. Sexual maturation was determined using salivary testosterone as an objective indicator. Normalized for body massVO_2max remained constant from 6 to 15 years (49 ml· min^–1 · kg^–1, SD 6), whilst P_max andP _30s increased from 6–8 to 14–15 years, from 6.2 W · kg^–1, SD 1.1 to 10.8 W · kg^–1, SD 1.4 and from 4.7 W · kg^–1, SD 1.0 to 7.6 W · kg^–1, SD 1.0, respectively, (P < 0.001). The ratio P_max: was 1.7 SD 3.0 at 6–8 years and reached 2.8 SD 0.5 at 14–15 years and the ratioP _30s: changed similarly from 1.3 SD 0.3 to 1.9 SD 0.3. In contrast, the ratio P_max:P _30s remained unchanged (1.4 SD 0.2). Significant relationships (P < 0.001) were observed between P_max (W · kg^–1),P _30s (W · kg^–1), blood lactate concentrations after the Wingate test, and age, height, mass and salivary testosterone concentration. This indicates that growth and maturation have together an important role in the development of anaerobic metabolism.     

Relationships of the anaerobic threshold with the 5 km, 10 km,and 10 mile races

Summary The purpose of present study was to assess the relationship between anaerobic threshold (AT) and performances in three different distance races (i.e., 5 km, 10 km, and 10 mile). AT, O₂ max, and related parameters for 17 young endurance runners aged 16–18 years tested on a treadmill with a discontinuous method. The determination of AT was based upon both gas exchange and blood lactate methods. Performances in the distance races were measured within nearly the same month as the time of experiment. Mean AT- O₂ was 51.0 ml·kg^–1·min^–1 (2.837 l·min^–1), while O₂ max averaged 64.1 ml·kg^–1·min^–1 (3.568 l·min^–1). AT-HR and %AT (AT- O₂/ O₂ max) were 174.7 beats·min^–1 and 79.6%, respectively. The correlations between O₂ max (ml·kg^–1·min^–1) and performances in the three distance races were not high (r=–0.645, r=–0.674, r=–0.574), while those between AT- O₂ and performances was r=–0.945, r=–0.839, and r=–0.835, respectively. The latter results indicate that AT- O₂ alone would account for 83.9%, 70.4%, and 69.7% of the variance in the 5 km, 10 km, and 10 mile performances, respectively. Since r=–0.945 (5 km versus AT- O₂) is significantly different from r=–0.645 (5 km versus O₂ max), the 5 km performance appears to be more related to AT- O₂ than VO₂ max. It is concluded that individual variance in the middle and long distance races (particularly the 5 km race) is better accounted for by the variance in AT- O₂ expressed as milliliters of oxygen per kilogram of body weight than by differences in O₂ max.     

The relative influence of body characteristics on humid heat stress response

The present study was designed to determine the relative importance of individual characteristics such as maximal oxygen uptake ( O_2max), adiposity, DuBois body surface area (A _D), surface to mass ratio (A _D: mass) and body mass, for the individual's reaction to humid heat stress. For this purpose 27 subjects (19 men, 8 women), with heterogeneous characteristics ( O_2max 1.86–5.28 1 · min^–1; fat% 8.0%–31.9%; mass 49.8–102.1 kg; A _D 1.52–2.33 m²) first rested (30 min) and then exercised (60 W for 1 h) on a cycle ergometer in a warm humid climate (35°C, 80% relative humidity). Their physiological responses at the end of exercise were analysed to assess their relationship with individual characteristics using a stepwise multiple regression technique. Dependent variables (with ranges) included final values of rectal temperature (T _re 37.5–39.0°C), mean skin temperature (T _sk 35.7–37.5°C), body heat storage (S 3.2–8.1 J · g^–1), heart rate (HR 100–172 beat · min^–1), sweat loss (397–1403g), mean arterial blood pressure (BP_a, 68–96 mmHg), forearm blood flow (FBF, 10.1–33.9 ml · 100ml^–1 · min^–1) and forearm vascular conductance (FVC = FBF/BP_a, 0.11–0.49 ml · 100 ml^–1 · min^–1 · mmHg^–1). The T _re, T _sk and S were (34%–65%) determined in the: main by ( O_2max), or by exercise intensity expressed as a percent age of O_2max (% O_2max). For T _re, A _D: mass ratio also contributed to the variance explained, with about half the effect of ( O_2max), For T _sk, fat% contributed to the variance explained with about two-third the effect of O_2max. Total body sweat loss was highly dependent (50%) on body size (A _D or mass) with regular activity level having a quarter of the effect of body size on sweat loss. The HR, similar to T _re, was determined by O_2max (48%–51%), with less than half the effect of A _D or A _D :mass (20%). Other circulatory parameters (FBF, BP_a, FVC) showed little relationship with individual characteristics ( < 36% of variance explained). In general, the higher the ( O_2max), and/or the bigger the subject, the lower the heat strain observed. The widely accepted concept, that body core temperature is determined by exercise intensity expressed as % O_2max and sweat loss by absolute heat load, was only partially supported by the results. For both variables, other individual characteristics were also shown to contribute.     

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.     

Relationship of middle cerebral artery blood flow velocity to intensity during dynamic exercise in normal subjects

Summary Cerebral blood flow has been reported to increase during dynamic exercise, but whether this occurs in proportion to the intensity remains unsettled. We measured middle cerebral artery blood flow velocity (m) by transcranial Doppler ultrasound in 14 healthy young adults, at rest and during dynamic exercise performed on a cycle ergometer at a intensity progressively increasing, by 50 W every 4 min until exhaustion. Arterial blood pressure, heart rate, end-tidal, partial pressure of carbon dioxide (P _ETCO₂), oxygen uptake ( O₂) and carbon dioxide output were determined at exercise intensity. Mean vM increased from 53 (SEM 2) cm · s^–1 at rest to a maximum of 75 (SEM 4) cm · s^–1 at 57% of the maximal attained O₂( O_2max), and thereafter progressively decreased to 59 (SEM 4) cm · s^–1 at O_2max. The respiratory exchange ratio (R) was 0.97 (SEM 0.01) at 57% of O_2maxand 1.10 (SEM 0.01) at O_2max. The P _ETCO₂ increased from 5.9 (SEM 0.2) kPa at rest to 7.4 (SEM 0.2) kPa at 57% of O_2maxand thereafter decreased to 5.9 (SEM 0.2) kPa at O_2max. Mean arterial pressure increased from 98 (SEM 1) mmHg (13.1 kPa) at rest to 116 (SEM 1) mmHg (15.5 kPa) at 90% of O_2max, and decreased slightly to 108 (SEM 1) mmHg (14.4 kPa) at O_2max. In all the subjects, the maximal value of v _m was recorded at the highest attained exercise intensity below the anaerobic threshold (defined by R greater than 1). We concluded that cerebral blood flow as evaluated by middle cerebral artery flow velocity increased during dynamic exercise as a function of exercise intensity below the anaerobic threshold. At higher intensities, cerebral blood flow decreased, without however a complete return to baseline values, and it is suggested that this may have been at least in part explained by concomitant changes in arterial PCO₂.     

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.     

Adaptations to training at the individual anaerobic threshold

Summary The individual anaerobic threshold (Th_an) is the highest metabolic rate at which blood lactate concentrations can be maintained at a steady-state during prolonged exercise. The purpose of this study was to test the hypothesis that training at the Th_an would cause a greater change in indicators of training adaptation than would training around the Th_an. Three groups of subjects were evaluated before, and again after 4 and 8 weeks of training: a control group, a group which trained continuously for 30 min at the Th_an intensity (SS), and a group (NSS) which divided the 30 min of training into 7.5-min blocks at intensities which alternated between being below the Th_an [Th_an–30% of the difference between Th_an and maximal oxygen consumption ( )] and above the Than (Th_an + 30% of the difference between Th_an and ). The increased significantly from 4.06 to 4.271 · min^–1 in SS and from 3.89 to 4.061-min^–1 in NSS. The power output (W) at Th_an increased from 70.5 to 79.8% in SS and from 71.1 to 80.7% in NSS. The magnitude of change in ,W at Th_an, % at Th_an and in exercise time to exhaustion at the pretraining Th_an was similar in both trained groups. Vastus lateralis citrate synthase and 3-hydroxyacyl-CoA-dehydrogenase activities increased to the same extent in both trained groups. While all of these training-induced adaptations were statistically significant (P<0.05), there were no significant changes in any of these variables for the control subjects. These results suggest that the relative stimulus for physiological adaptation to training was similar in SS and NSS. These results also demonstrate that, when training intensity is set relative to the Th_an, it is the mean intensity during training that determines the extent of adaptation regardless of whether the exercise is performed intermittently or continuously.     

Cardiorespiratory adaptation with short term training in older men

Summary The purpose of this study was to assess the rate of training-induced cardiorespiratory adaptations in older men [mean (SD), 66.5 (1.2) years]. The eight subjects trained an average of 4.3 (0.3) times each week. The walk/jog training was in two phases with 4 weeks (phase 1) at a speed to elicit 70% of pre-training maximal oxygen consumption ( ), and 5 weeks (phase 2) at 80%. Maximal exercise treadmill tests and a standardized submaximal protocol were performed prior to training, at weekly intervals during the training programme, and after training. (ml·kg^–1·min^–1) increased significantly over both phases: 6.6% after the first 4 weeks, and an additional 5.2% after the final 5 weeks. The weekly changes in over phase 1 were well fitted by an exponential association curve (r=0.75). The half-time for the rate of adaptation was 13.8 days, or 8.3 training sessions. Over phase 2, the change in did not plateau and a time course could not be determined. Submaximal exercise heart rate (f _c ) was reduced a significant 10 beats · min^–1 after the first 4 weeks, and a further 6 beats · min^–1 over the final 5 weeks. Thef _c reductions showed half-times of 9.1 days (phase 1) and 9.8 days (phase 2) (or 5-6 training sessions). The anaerobic ventilation threshold was increased 13.9% over the 9 weeks of training and the respiratory exchange ratio during constant load heavy exercise was significantly reduced; however, these changes could not be described by an exponential time course. Thus, short-term exercise training of older men resulted in significant and rapid cardiorespiratory improvements.     

Effect of physical training on the responses of serum adrenocorticotropic hormone during prolonged exhausting exercise

Summary The purpose of this study was to investigate the effects of physical training on the responses of serum adrenocorticotropic hormone (ACTH) and cortisol concentration during low-intensity prolonged exercise. Five subjects who had fasted for 12 h cycled at the same absolute intensity that elicited 50% of pre-training maximal oxygen uptake ( O_2max), either until exhaustion or for up to 3 h, before and after 7 weeks of vigorous physical training [mean daily energy consumption during training exercise, 531 kcal (2230 kJ)]. In the pre-training test, serum ACTH and cortisol concentrations did not increase during the early part of the exercise. Increases in concentrations of both hormones occurred in all subjects when blood glucose concentration decreased during the later phase of the exercise. The mean values and SEM of serum ACTH and cortisol concentrations at the end of the exercise were 356 ng · l^–1, SEM 79 and 438 g · l^–1, SEM 36, respectively. After the physical training, O_2max of the subjects improved significantly from the mean value of 50.2 ml · kg^–1 · min^–1, SEM 2.5 to 57.3 ml · kg^–1 · min^–1, SEM 2.0 (P < 0.05). In the post-training test, exercise time to exhaustion was prolonged in three subjects. Comparing the pre- and post training values observed after the same length of time that the subjects had exercised in the pre-training test, the post-training values of serum ACTH (44 ng · l^–1, SEM 3) and cortisol (167 g · l^–1, SEM 30) concentration were less than the pre-training value (P < 0.05). However, after the subjects stopped exercising in the post-training test, the serum ACTH (214 ng · l^–1, SEM 49) and cortisol (275 g · l^–1, SEM 50) concentrations were not significantly different from those measured after the subjects stopped exercising in the pre-training test (P > 0.10). In conclusion, high-intensity physical training reduced the responses of both hormones during prolonged exercise, propbably because of a delayed decrease of blood glucose concentration after physical training, while the level of the blood glucose concentration which induces ACTH and cortisol secretion did not change.