A study was conducted to elucidate the changes in circulatory responses to sudden strenuous exercise (SSE) using beat-by-beat analysis of heart rate (HR), stroke volume (SV) and blood pressure (BP) . The effects of warming-up on these responses were also studied.
Six healthy male students volunteered for the study. A bicycle ergometer was prepared for SSE. The intensity and duration of SSE were 100% VO₂max and 1 min, respectively. Warming-up of 80% VO₂max for 5 min followed by SSE. The interval between SSE and warming-up varied from 5 to 30 min. A control experiment was also performed without warming-up.
The main results obtained were as follows :
1) BP decreased in the initial stage of SSE, followed by a steep increase. This temporary drop in BP was prevented by warming-up. This might contribute to the prevention of myocardial ischemia which is occasionally observed in the initial stage of SSE without warming-up.
2) Time constants of HR and SV during SSE were shortened by warming-up with long intervals, while the time constant of BP was shortened when the interval was short.
3) The recovery response of each parameter was accelerated by warming-up, but the effect of warming-up had almost disappeared after a 30 min interval.
These results suggest the following conclusions :
Warming-up accelerates the up-stroke and recovery of circulatory responses to SSE, but these effects of warming-up are strongly influenced by interval time. In particular, the effect of recovery acceleration is almost abolished by a 30 min interval.

The purpose of the present study was to investigate the relationships between the peak running velocity, and aerobic and anaerobic capacity in incremental running in pre- and post-competitive season using eight long distance runners. Measurements were peak running velocity, VO_2max, running velocity and VO₂ at respiratory exchange ratio (RER) 1.0, and blood lactate after exhaustion in the incremental running test. Correlation analysis revealed that pre-season velocity at RER 1.0 and post-season blood lactate were both related to peak running velocity. Furthermore, change in peak running velocity was related to change in blood lactate between pre-and post-season. These results suggest that factors that probably influenced running performance change from aerobic capacity in the pre-season to anaerobic capacity in the post-season, and that running performance during the competitive season may be highly dependent upon anaerobic capacity.

To obtain a viewpoint concerning evaluation of endurance type of athletes, we investigated the difference in physiological responses between middle- and long-distance runners in an incremental running test. Measurements were VO₂max and time of its appearance, change of VO₂ from 1.5 min before exhaustion to exhaustion (ΔVO₂), heart rate (HR), and blood lactate after exhaustion.
Results were as follows.
(1) The time of VO₂ max appearance in the middle distance runners was earlier than in the long distance runners.
(2) VO₂max was significantly higher in the long distance runners than in the middle distance runners.
(3) Blood lactate after exhaustion and HRmax were significantly higher in the middle distance runners than in the long distance runners.
(4) Blood lactate after exhaustion was significantly related to ΔVO₂ (r =-0.660, P<0.05) .
These findings suggest that the endurance type of athletes could be evaluated from the time of VO₂max appearance, blood lactate after exhaustion and HRmax in incremental running, and that VO₂max appearance may be effected by high blood lactate accumulation.

The purpose of this study was to investigate the relationship between 2-min kayak ergometer performance (KEP) and energy supply capacity. Seventeen (male : 9, female : 8) kayak paddlers completed a maximal incremental test to determine aerobic capacity{maximal oxygen uptake (VO_2max) and lactate threshold (LT)}, and a 2-min all-out test to measure performance and anaerobic capacity{maximal accumulated oxygen deficit (MAOD)}. In addition, total energy supply capacity was estimated by these variables [{(T-score of VO_2max+T-score of LT)/2+T-score of MAOD}/2]. Oxygen uptake and blood lactate concentrations were continuously measured during the incremental test and at the completion of both tests. These tests were conducted on an air-braked kayak ergometer. Unlike the previous research, no significant relationships were found between KEP and VO_2max and LT in either male or female. MAOD correlated with KEP in female (r=0.75, p<0.05), but not in male. On the other hand, there was a significant correlation between KEP and total energy supply capacity (r=0.89, p<0.05, both male and female). In conclusion, total energy supply capacity accounted for a large part of KEP. These results indicate that flat-water kayak paddlers need to develop both aerobic and anaerobic capacities.

The purposes of this study were to investigate the characteristics of physiological responses during flat-water kayaking events, and to quantify the contribution of aerobic and anaerobic energy systems. Eight male kayak paddlers participated in the study. The subjects performed an incremental test and five all-out tests (20, 40, 120, 240 and 600 sec) on a kayak ergometer. Peak oxygen uptake (VO₂peak ; 3790 ml · min^-1) in the incremental test was significantly lower than maximal oxygen uptake (VO₂max ; 3944 ml · min^-1) in the all-out test. In contrast, power at VO₂peak (154.0 W) was significantly higher than power at VO₂max (144.1 W). The contributions of energy systems were calculated by measurements of the accumulated oxygen uptake and accumulated oxygen deficit. The relative anaerobic energy system contributions for 200 m(40 sec), 500 m (120 sec), and1000 m (240 sec) averaged 71%, 43%, and 26%, respectively. These higher relative anaerobic energy system contributions, due to higher anaerobic capacity in kayak athletes, and the smaller muscle mass involved in kayak paddling limit oxygen uptake when exercise intensity is high. Furthermore, slower exercise cadence in kayak paddling leads to higher muscular tension, and thus may enhance the limiting of oxygen uptake.

The purpose of this study was to determine the difference in the attainment rate of maximal oxygen uptake in cycling and running (%cycVO_2max). Seven healthy male subjects (22.9±1.3 yrs, 171.9±4.7 cm, 61.0±5.2 kg) participated in a maximal incremental exercise test for running and cycling. During the exercise testing, oxygen uptake, carbon dioxide output, respiratory exchange rate, minute ventilation, tidal volume, respiratory rate, and heart rate were measured. Attainment rates of each physiological measurement for cycling and running were shown as %cycVO_2max, %cycVCO_2max, %cycRER_max, %cycVE_max, %cycVt, %cycRR and %cycHR_max. Transverse relaxation time (T2)-weighted spin echo images were acquired before and after the exercise periods. Exercise-induced T2 values of each muscle and muscle-group are indices of muscular activity level, so the difference between the T2 value of cycling and running in each muscle or muscle group was shown as ΔT2_%. VO_2max in cycling was 92.2% of VO_2max in running. Significant correlations were observed between %cycVO_2max and %cycVCO_2max, %cycVO_2max and %cycRR. Furthermore, significant correlations were recognized between %cycVO_2max and ΔT2_% of the m. quadriceps femoris, %cycVCO_2max and ΔT2_% of the m. quadriceps femoris, %cycVCO_2max and the m. triceps surae, as well. These results show that the higher muscular activity level of the thigh in cycling increases the uptake of oxygen in the muscle. The T2 value shows that the uptake or redistribution of fluid within muscle is driven by the accumulation of lactate and inorganic phosphate. Therefore, the T2 value of maximal incremental exercise would reflect the anaerobic capacity of the muscle. Judging from the significant correlations between %cycVO_2max and %cycVCO_2max or %cycRR, the anaerobic capacity of each subject would also affect the difference between the maximal oxygen uptake of cycling and running.

The purpose of this study was to investigate the effects of contraction force and the pooled blood volume in the calf on the pumping action of calf muscle contraction. Calf blood volume was controlled by lower body negative pressure (LBNP) and isometric contraction of calf extensor muscle was performed using a handmade dynamometer in recumbent position. The relative volume changes (ΔV/V%) of calf were determined using rubber straingage, when isometric contractions (5, 10, 20, 40 and 60 kg) of the calf muscle were repeated under LBNP of 0, -20, -40, and -60 mmHg.
During resting condition, Δ V/V was increased by 1.04% under -20 mmHg LBNP, 1.88% under -40 mmHg, and 2.54% under -60 mmHg. These increases of ΔV/V were due to the increased blood pooling in the calf. It was shown that the increased blood volume was almost expelled by several bouts of muscle contractions of proper force. The optimum force of contractions for expelling pooled blood was 20 kg under -20mmHg LBNP, and 40 kg under -40 and -60 mmHg LBNP. And it was apparent that the effectiveness of muscle pump was accumulated with repeating contractions, arriving to a plateau after several bouts.
It was shown that the effect of muscle pump in the given contraction force was more effective under the condition with more amount of blood contained in the calf, but the muscle pumping action by light contraction forces couldn't overcome the effect of severe LBNP.

The purpose of this study was to elucidate the changes in systolic and diastolic time intervals which accrue along with increase of HR during a prolonged exercise.
Fifteen male collegiate distance runners performed bicycle ergometer exercise of 70% maximal oxygen intake for 60 minutes. Electrocardiogram, phonocardiogram, pulse wave using ear densitogram and its derivative were recorded throughout the exercise, and then HR, STI, DT (diastolic time) and QS₂/DT were caluculated from the tracings.
The results obtained are as follows:
1. At the initial phase of the exercise, DT decreased markedly to result in rapid increase of QS₂/DT. When HR was between 130-150 beats/min, however, the rate of decrease of QS₂ was greater than that of DT, so QS₂/DT showed a tendency to decrease. When HR was more than 150, QS₂ reached a plateau but DT still continued to decrease, and QS₂/DT turned to increase again.
2. LVET decreased slowly throughout the exercise, whereas PEP decreased rapidly within initial two minutes and kept a steady state thereafter. The change in QS₂ after two minutes of exercise seemed to depend on LVET.
3. LVETi and QS₂i showed a similar change as that in QS₂/DT but the change in QS₂i was less obvious than that in LVETi.
4. PEN and PEP/LVET decreased rapidly in the initial two minutes, thereafter they continued to increase more slowly with increase of HR until the end of exercise.
Conclusively, HR continued to increase monotonously during prolonged exercise of a constant intensity, while systolic and diastolic time intervals varied the directions and patterns of their changes during the exercise.

A study was performed to investigate the validity of the derivative of the ear densitogram for measurement of left ventricular ejection time (LVET) .
Nine male college students performed bicycle exercise at an initial work load of 0 watt (W), subsequently increasing by 60W every 3 min up to 240W. The LVET derived from the derivative of the ear densitogram (LVETe) was compared with that derived from the carotid pulse wave (LVETc) obtained at the same time.
The results were as follows:
1. There was a high correlation coefficient, r=0.987 (P<0.01), between LVETe and LVETc.
2. At rest, LVETe showed a tendency to coincide with LVETc. In contrast, LVETe became longer than LVETc during exercise, and the higher HR became, the larger the difference between the two.
3. In the individual regression equations between LVETe and LVETc, the slopes and the intercepts were nearly identical.
4. The following equation was proposed for the correction of LVETe during exercise. LVET=-0.147⋅HR+ LVETe+ 8.3
From these findings, it was concluded that the validity of the derivative of the ear densitogram for estimation of LVET is sufficiently high. LVETe at rest is valid for the estimation of LVET without correction. During exercise, however, LVETe shows a tendency to be longer than LVETc, and thus it is desirable to correct LVETe using the above equation.

A study was undertaken to determine whether the specific change in the ratio of systolic to diastolic time (QS₂/DT) observed during prolonged exercise¹⁷⁾ is dependent on HR or elapsed time, and also to elucidate the possible relationship between change in QS₂/DT and distance-running performance. Twelve male distance runners were divided into two groups, a high- (HP Group) and a low-performance (LP Group) group, according to their 10, 000-meter running performance. They performed 60-min exercise on a bicycle ergometer at a work load controlled so as to keep the HR at 150 bpm. HR, systolic time intervals (STIs) and DT were calculated from electrocardiogram, phonocardiogram and the derivative of ear densitogram.
In the time course of QS₂/DT, two crests were formed at 2 and 15 min after the start of exercise, and also two troughs were formed at 10 and 20 min. Some of these troughs and crests formed even when HR was kept constant. Patterns of change in QS₂, DT, QS₂/DT and other parameters were similar in the two groups. However, the absolute values of the parameters differed. QS₂, left ventricular ejection time (LVET) and QS₂/DT in the HP Group were lower than those in the LP Group, whereas DT in the HP Group was longer than that in the LP Group.
From these findings, it was concluded that the specific change seen in QS₂/DT during prolonged exercise is dependent not on the HR level but on elapsed time. The changes in STIs and DT during prolonged exercise are thus influenced by the distance-running performance of the subjects.