Biomedical subjects

M Udo

Publications and source records attributed to M Udo.

At least 19 recordsLinked to original sources

PubMed1994

Climbing fiber responses in cerebellar vermal Purkinje cells during perturbed locomotion in decerebrate cats.

We recorded spike potentials from Purkinje cells in the lateral vermis of lobule V in cat cerebellum, and found significant enhancement in climbing fiber discharges during perturbed locomotion. Five adult cats were decerebrated at a precollicular level, and 4-5 days thereafter, they were mounted on a treadmill. During stable locomotion at 36 cm/s belt velocity, climbing fiber responses were slightly modulated with a weak increment at the swing phase of the ipsilateral forelimb. When the left contralateral forelimb alone was suddenly imposed with a faster belt velocity of 61 cm/s, the occurrence of the climbing fiber discharges was significantly enhanced during the late swing phase of the ipsilateral forelimb. This observation is in accordance with the general notion that climbing fiber responses represent error signals in control of movements.

Animals↗

PubMed1993

Does critical swimming velocity represent exercise intensity at maximal lactate steady state?

The purpose of this investigation was to determine whether the critical swimming velocity (vcrit), which is employed in competitive swimming, corresponds to the exercise intensity at maximal lactate steady state. vcrit is defined as the swimming velocity which could theoretically be maintained forever without exhaustion and expression as the slope of a regression line between swimming distances covered and the corresponding times. A total of eight swimmers were instructed to swim two different distances (200 m and 400 m) at maximal effort and the time taken to swim each distance was measured. In the present study, vcrit is calculated as the slope of the line connecting the two times required to swim 200 m and 400 m. vcrit determined by this new simple method was correlated significantly with swimming velocity at 4 mmol.l-1 of blood lactate concentration (r = 0.914, P < 0.01) and mean velocity in the 400 m freestyle (r = 0.977, P < 0.01). In the maximal lactate steady-state test, the subjects were instructed to swim 1600 m (4 x 400 m) freestyle at three constant velocities (98%, 100% and 102% of vcrit). At 100% vcrit blood lactate concentration showed a steady-state level of approximately 3.2 mmol.l-1 from the first to the third stage and at 98% of vcrit lactate concentration had a tendency to decrease significantly at the fourth stage. On the other hand, at 102% of vcrit, blood lactate concentration increased progressively and those of the third and fourth stages were significantly higher than those at 100% of vcrit (P < 0.05). These data suggest that vcrit, which can be calculated by performing two timed, maximal effort swimming tests, may correspond to the exercise intensity at maximal lactate steady state.

Adolescent↗

PubMed1993

Relationship between cardiac output and oxygen uptake at the onset of exercise.

The purpose of the present study was to assess the relationship between the rapidity of increased gas exchange (i.e. oxygen uptake VO2) and increased cardiac output (Qc) during the transient phase following the onset of exercise. Five healthy male subjects performed multiple rest-exercise or light exercise (25 W)-exercise transitions on an electrically braked ergometer at exercise intensities of 50, 75, or 100 W for 6 min, respectively. Each transition was performed at least eight times for each load in random order. The VO2 was obtained by a breath-by-breath method, and Qc was measured by an impedance method during normal breathing, using an ensemble average. On transitions from rest to exercise, VO2 rapidly increased during phase I with time constants of 6.8-7.3 s. The Qc also showed a similar rapid increment with time constants of 6.0-6.8 s with an apparent increase in stroke volume (SV). In this phase I, VO2 increased to about 29.7%-34.1% of the steady-state value and Qc increased to about 58.3%-87.0%. Thereafter, some 20 s after the onset of exercise a mono-exponential increase to steady-state occurred both in VO2 and Qc with time constants of 26.7-32.3 and 23.7-34.4 s, respectively. The insignificant difference between Qc and VO2 time constants in phase I and the abrupt increase in both Qc and SV at the onset of exercise from rest provided further evidence for a "cardiodynamic" contribution to VO2 following the onset of exercise from rest.

Adult↗

PubMed1993

A new learning paradigm: adaptive changes in interlimb coordination during perturbed locomotion in decerebrate cats.

Adaptive interlimb coordination was studied during perturbed locomotion in experimental chronically decerebrate cats. Perturbations were applied to the stance phases of the left forelimb using a newly developed treadmill which consisted of three compartments, one each for the left forelimb, the left hindlimb and both right limbs. During the perturbed locomotion, the treadmill belt for the left forelimb was driven at about twice the speed for the other limbs. During the first 1-50 perturbed steps, the step cycles of both forelimbs showed marked fluctuations; thereafter, the animals achieved stable locomotion by slightly shortening step cycle durations, and also by adjusting durations of bisupport phases asymmetrically in the left and right forelimbs. The present method provides a new test paradigm for adaptive interlimb coordination in locomotion, which will be useful in studying neural mechanisms of motor learning involving cerebellar synaptic plasticity.

Adaptation, Psychological↗

PubMed1993

Physiological characteristics related to endurance running performance in female distance runners.

The purpose of the present study was to determine the relationships between running velocity (v) in a 3000-m race and various physiological parameters. The parameters measured among 57 female distance runners during a treadmill running test were v at the lactate threshold (v-Tlac), oxygen uptake (VO2) at the lactate threshold (VO2 at Tlac), v at the onset of blood lactate accumulation (v-OBLA), VO2 at OBLA, running economy (steady-state VO2 at a standard v of 4 m s-1), maximal oxygen uptake (VO2 max) and v at VO2 max (v-VO2 max). The v-OBLA was the blood lactate variable with the strongest correlation with v in a 3000-m race (r = 0.78, P < 0.001). The second strongest correlation was with v-Tlac (r = 0.77, P < 0.001). Although v-VO2 max was strongly correlated with v over 3000 m (r = 0.75, P < 0.001), further analysis by stepwise multiple regression indicated that a combination of v-OBLA, VO2 at Tlac and v-Tlac could account for 73.2% of the variability in v over 3000 m, whereas v-OBLA on its own explained 61.5%. Blood lactate variables can account for a reasonably large part of the variance in v over 3000 m. Also, v-VO2 max can be used as a non-invasive predictor of distance running performance.

Adolescent↗

PubMed1992

Day-to-day changes in oxygen uptake kinetics at the onset of exercise during strenuous endurance training.

The aim of this study was to assess the effect of strenuous endurance training on day-to-day changes in oxygen uptake (VO2) on-kinetics (time constant) at the onset of exercise. Four healthy men participated in strenuous training for 30 min.day-1, 6 days.week-1 for 3 weeks. The VO2 was measured breath-by-breath every day except Sunday at exercise intensities corresponding to the lactate threshold (LT) and the onset of blood lactate accumulation (OBLA) which were obtained before training. Furthermore, an incremental exercise test was performed to determine LT, OBLA and maximal oxygen uptake (VO2max) before and after the training period and every weekend. The 30-min heavy endurance training was performed on a cycle ergometer 5 days.week-1 for 3 weeks. Another six men served as the control group. After training, significant reductions of the VO2 time constant for exercise at the pretraining LT exercise intensity (P less than 0.05) and at OBLA exercise intensity (P less than 0.01) were observed, whereas the VO2 time constants in the control group did not change significantly. A high correlation between the decrease in the VO2 time constant and training day was observed in exercise at the pretraining LT exercise intensity (r = -0.76; P less than 0.001) as well as in the OBLA exercise intensity (r = -0.91; P less than 0.001). A significant reduction in the blood lactate concentration during submaximal exercise and in the heart rate on-kinetics was observed in the training group.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1992

Determination and validity of critical velocity as an index of swimming performance in the competitive swimmer.

The purpose of this investigation was to test whether the concept of critical power used in previous studies could be applied to the field of competitive swimming as critical swimming velocity (vcrit). The vcrit, defined as the swimming velocity over a very long period of time without exhaustion, was expressed as the slope of a straight line between swimming distance (dlim) at each speed (with six predetermined speeds) and the duration (tlim). Nine trained college swimmers underwent tests in a swimming flume to measure vcrit at those velocities until the onset of fatigue. A regression analysis of dlim on tlim calculated for each swimmer showed linear relationships (r2 greater than 0.998, P less than 0.01), and the slope coefficient signifying vcrit ranged from 1.062 to 1.262 m.s-1 with a mean of 1.166 (SD 0.052) m.s-1. Maximal oxygen consumption (VO2max), oxygen consumption (VO2) at anaerobic threshold, and the swimming also velocity at the onset of blood lactate accumulation (vOBLA) were also determined during the incremental swimming test. The vcrit showed significant positive correlations with VO2 at anaerobic threshold (r = 0.818, P less than 0.01), vOBLA (r = 0.949, P less than 0.01) and mean velocity of 400 m freestyle (r = 0.864, P less than 0.01). These data suggested that vcrit could be adopted as an index of endurance performance in competitive swimmers.

Adolescent↗

PubMed1992

A simple method for determining critical speed as swimming fatigue threshold in competitive swimming.

The purpose of this investigation was to determine whether the concept of the critical power could be applied to competitive swimming by using critical swimming speed (CS) as determined both in the swimming flume (CS-flume) and in the normal swimming pool (CS-pool) and whether CS could be utilized as a practical index for assessing a swimmer's endurance performance. CS defined as the swimming speed which could be theoretically maintained continuously without exhaustion was expressed as the slope of a regression line between swimming distance (D) and its duration (T) obtained at various swimming speeds. Eight highly trained swimmers were instructed to swim until onset of fatigue at four predetermined swimming speed levels in the swimming flume and at maximal effort over four different swimming distances in the swimming pool. In the results of CS-flume and CS-pool, the regression relations between D and T were expressed in the general form, D = a+b x T, with r2 being higher than 0.998 (p less than 0.01), respectively. These results both from the flume and the pool indicated extremely good linearity. Furthermore, maximal oxygen uptake (VO2max) during the incremental exercise test, swimming speed corresponding 4 mM of blood lactate concentration (V-OBLA) and mean velocity in the 400 m freestyle (V-400) were measured on each subject.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1992

[Estimation of energy expenditure and the validity of pitch counting during walking and jogging by piezoelectric materials].

The purpose of the present study was to assess the validity of Piezo-electric accelerometer for estimating energy expenditure in walking and jogging. Energy consumption by oxygen uptake was determined during steady state level of treadmill walking at the speed of 60, 80 and 100 m/min and jogging at the speed of 100, 120, 140, and 160 m/min for 10 subjects. There was a highly significant correlation between the energy consumption and the estimated energy expenditure by an accelerometer despite the attached position (r = 0.912 at the waist, r = 0.915 at the chest, P < 0.001), which suggests accurate estimating energy expenditure in the field.

Adult↗

PubMed1991

Ventilatory response and arterial potassium concentration during incremental exercise in patients with chronic airways obstruction.

The relationship of ventilation response (VE) to arterial potassium concentration (K+) during ramp incremental exercise was assessed in nine patients with chronic obstructive pulmonary disease (COPD), and in 10 healthy subjects. For COPD patients the maximum oxygen uptake (VOmax) was 19.6 +/- 3.8 ml kg-1 min-1 (+/- SD), and percentage of forced expired volume at 1 s (% FEV1) was 47.8 +/- 10.4%. In healthy subjects, VO2max was 44.4 +/- 7.0 ml kg-1 min-1 and FEV1 was 89.7 +/- 7.4%. Breath-by-breath determinations for VE, oxygen uptake (VO2) and carbon dioxide output (VCO2), as well as determinations for K+, partial pressure of oxygen (PO2), partial pressure of carbon dioxide (PCO2), pH and lactate in arterial blood were performed during a workout on an exercise bicycle at a ramp function work rate of 20 W min-1, preceded by a 40 min warm-up period. The major findings in the present study are: (1) that there is a linear relation between ventilation and arterial K+ concentration during ramp exercise in both healthy subjects and COPD patients; (2) that the slope of the VE-K+ relationship is significantly lower in COPD patients (16.2 +/- 7.3 l min-1 mM-1) than in normal subjects (37.4 +/- 6.9 l min-1 mM-1, P less than 0.01); and, (3) that the slope of the VE-K+ relationship is significantly related to the ability to ventilate during maximal exercise in both healthy subjects and COPD patients (P less than 0.05). It is thought that the significantly reduced slope of the VE-K+ relationship in the COPD patients could be interpreted as a reduced sensitivity to the stimulus and/or as a mechanical impairment of the ventilation.

Adolescent↗

PubMed1990

Relationship between ventilation and arterial potassium concentration during incremental exercise and recovery.

The purpose of this study was to compare the relationship of ventilation (VE) with pH, arterial concentrations of potassium [( K+]a), bicarbonate [( HCO3-]a), lactate [( la]a), and acid-base parameters which would affect hyperpnoea during exercise and recovery. To assess this relationship, ten healthy male subjects exercised with intensity increasing as a ramp function of 20 W.min-1 until voluntary exhaustion and they were then allowed a 5-min recovery period. Breath-by-breath gas exchange data, [HCO3-]a, pH, [la]a, [K+]a and blood gases were determined during both exercise and recovery. Using a linear regression method, the VE/[K+]a relationship was analysed during both exercise and recovery. Several interesting results were obtained: a significant relationship between [K+]a and VE was observed during recovery as well as during exercise; the VE at any given values of [K+]a was significantly higher during recovery than during exercise and out of those factors affecting exercise hyperpnoea, only [K+]a had a similar time-course to VE during recovery. Changes in [K+]a during recovery were shown to occur significantly faster than VE with an [K+]a time constant of 70.0 s, SD 16.2 as opposed to 105.5 s, SD 10.0 for VE (P less than 0.01). These results provided further evidence that [K+]a might play an important role as a substance which can stimulate exercise hyperpnoea as has been suggested by other workers. The present study also showed that during recovery [K+]a contributed significantly to the control of VE.

Adult↗

PubMed1990

Specificity of physiological adaptation to endurance training in distance runners and competitive walkers.

The present study was designed to evaluate the specificity of physiological adaptation to extra endurance training in five female competitive walkers and six female distance runners. The mean velocity (v) during training, corresponding to 4 mM blood lactate [onset of blood lactate accumulation (OBLA)] during treadmill incremental exercise (training v was 2.86 m.s-1, SD 0.21 in walkers and 4.02 m.s-1, SD 0.11 in runners) was added to their normal training programme and was performed for 20 min, 6 days a week for 8 weeks, and was called extra training. An additional six female distance runners performed only their normal training programme every day for about 120 min at an exercise intensity equivalent to their lactate threshold (LT) (i.e. a running v of about 3.33 m.s-1). After the extra training, there were statistically significant increases in blood lactate variables (i.e. oxygen uptake (VO2) at LT, v at LT, VO2 at OBLA, v at OBLA; P less than 0.05), and running v for 3,000 m (P less than 0.01) in the running training group. In the walking training group, there were significant increases in blood lactate variables (i.e., v at LT, v at OBLA; P less than 0.05), and walking economy. In contrast, there were no significant changes in lactate variables, running v and economy in the group of runners which carried out only the normal training programme. It is suggested that the changes in blood lactate variables such as LT and OBLA played a role in improving v of both the distance runners and the competitive walkers.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗

PubMed1990

Significance of the contribution of aerobic and anaerobic components to several distance running performances in female athletes.

To assess the most important determinant for successful distance running (800 m, 1500 m and 3000 m events) in female athletes, measurements of several anaerobic indices were made (peak power, mean power) using the Wingate anaerobic test (WAnT), and aerobic indices such as oxygen uptake (VO2) or running velocity (v) at lactate threshold (LT), VO2 or v at onset of blood lactate accumulation (OBLA), running economy (RE), and maximal oxygen uptake were determined using the incremental treadmill test. The RE was represented by a VO2 value measured at 240 m.min-1 of a standard treadmill velocity. A stepwise multiple regression analysis (SAS stepwise procedure) combined the best features of forward inclusion and backward elimination to determine the most important factors in predicting the performance of running these distances as dependent variables. The stepwise procedure showed that the blood lactate variables such as LT and/or OBLA are highly correlated with, and contributed to predicting performance running 800 m-3000 m, whereas the anaerobic component was related only to running 800 m. In conclusion, blood lactate variables account for a large part of the variation in distance running performance in female as in male runners. The component of the anaerobic system which can be measured by the WAnT was shown to contribute to performance in running 800 m, but not in longer distances.

Adult↗

PubMed1990

[Estimation of energy expenditure during walking and jogging by using an electro-pedometer].

Using an electro-pedometer which is commercially available, energy expenditure during walking and/or jogging was assessed, and was compared with that obtained by oxygen uptake (VO2). Thirteen male students and 12 female students exercised on 6 minutes duration treadmill tests which velocities were 40, 60, 80, 100, and 120m/min for walking and 100, 120, 140, 160, and 180m/min for jogging, respectively. During exercise, energy expenditure was calculated by VO2 value and respiratory exchange ratio, and was estimated by an electro-pedometer. There was a significant linear relationship between energy expenditures estimated by the pedometer and calculated by VO2 during walking and jogging. To predict energy expenditure more precisely by the electro-pedometer, it is suggested that more precise value of stride should be inputted into the pedometer. In conclusion, the present study showed that commercially available electro-pedometer is able to use for the estimation of energy expenditure with precise validity during walking and/or jogging.

Adult↗

PubMed1989

Effect of hypoxia on arterial and venous blood levels of oxygen, carbon dioxide, hydrogen ions and lactate during incremental forearm exercise.

The purpose of the present study was to investigate whether, in humans, hypoxia results in an elevated lactate production from exercising skeletal muscle. Under conditions of both hypoxia [inspired oxygen fraction (F1O2): 11.10%] and normoxia (F1O2: 20.94%), incremental exercise of a forearm was performed. The exercise intensity was increased every minute by 1.6 kg.m.min-1 until exhaustion. During the incremental exercise the partial pressure of oxygen (PO2) and carbon dioxide (PCO2), oxygen saturation (SO2), pH and lactate concentration [HLa] of five subjects, were measured repeatedly in blood from the brachial artery and deep veins from muscles in the forearm of both the active and inactive sides. The hypoxia (arterial SO2 approximately 70%) resulted in (1) the difference in [HLa] in venous blood from active muscle (values during exercise-resting value) often being more than twice that for normoxia, (2) a significantly greater difference in venous-arterial (v-a) [HLa] for the exercising muscle compared to normoxia, and (3) a difference in v-a [HLa] for non-exercising muscle that was slightly negative during normoxia and more so with hypoxia. These studies suggest that lower O2 availability to the exercising muscle results in increased lactate production.

Adult↗

PubMed1989

Caudato-nigral transmission in the substantia nigra pars reticulata neurons changes with recovery from circling movements induced by microinfusion of ibotenic acid. I. Behavioral study.

Following creation of a unilateral circumscribed lesion in a portion of a cat substantia nigra pars reticulata by microinfusion of ibotenic acid, circling movements toward the contralateral side of the lesion appeared within 2 days and disappeared a few days later. After recovery, the circling movements reappeared when the cats were decerebrated at the premammillary and precollicular level, suggesting that brain centers rostral to the decerebration participate in compensating the circling movements.

Animals↗

PubMed1989

Caudato-nigral transmission in the substantia nigra pars reticulata neurons changes with recovery from circling movements induced by microinfusion of ibotenic acid. II. Electrophysiological study on synaptic transmission.

Caudato-nigral synaptic transmission was examined by stimulation of the caudate nucleus while recording from nigral neurons in cats recovering from circling movements induced by a unilateral circumscribed lesion in the substantia nigra pars reticulata after microinfusion of ibotenic acid. Extra- and intracellular recording from neurons in lesion-spared areas of the substantia nigra pars reticulata indicated that the caudato-nigral synaptic action on the side ipsilateral to the lesion exhibited a shorter duration of inhibition and a larger amplitude of excitation as a means of compensating for the circling movements.

Action Potentials↗

PubMed1989

Arterial blood gases, acid-base balance, and lactate and gas exchange variables during hypoxic exercise.

To determine the effect of hypoxia on lactate threshold (LT), onset of blood lactate accumulation (OBLA), and gas exchange threshold (GET), the lactate level together with VO2, VCO2, VE, and acid-base status in arterial blood from 12 female distance runners performing a progressive incremental treadmill test under the condition of hypoxic gas inhalation (HC: FIO2 is 16.0% in N2) compared with normoxic conditions (NC: FIO2 is 20.9%; i.e., air) were examined. During exercise, HC shifted LT, GET, and OBLA to a lower VO2 by 12.5%, 12.9%, and 9.3%, respectively. The GET during hypoxic exercise was well correlated with LT (GET = 0.973LT + 0.04; expressed in VO2 l.min-1). The close reciprocal changes in arterial blood lactate and bicarbonate (HCO3-) were observed during hypoxic as well as normoxic exercise. These findings provide evidence for the cause and effect relationship between LT and GET, even in hypoxic exercise. During submaximal exercise below the LT, PaCO2 and HCO3- slightly increased both in NC and HC with pH remaining unchanged. However, during exercise above the LT, the PaCO2, HCO3-, and pH all decreased with pH decreasing more markedly during hypoxia. In conclusion, this study demonstrated a clear increase in arterial lactate during hypoxic exercise above the LT. Both the LT and GET are shifted to a lower work rate by hypoxia in the same manner with the correlation between them remaining high, supporting the cause and effect relationship of these two parameters.

Acid-Base Equilibrium↗