Influence of the oxygen uptake slow component on the aerobic energy cost of high-intensity submaximal treadmill running in humans

The international health cooperation of Japan for developing countries has been mostly concentrated on matters such as improvement of hygienic environment, prevention of tropical infectious diseases, establishment of hospitals with modern medical instruments and devices, and dispatch of medical experts. PHC (Primary Health Care) activities based on voluntary participation of local inhabitants in developing countries have been largely neglected. In the field of health and medical care, sufficient effect may not be achieved unless the local health activity is based on voluntary participation of the inhabitants. The introduction of highly advanced modern medical techniques may be beneficial to some of the inhabitants, while most of the local inhabitants may not have the chance to receive such benefits, and additionally it is difficult to propagate modern medical care and technique widely to rural areas in Thailand. In Thailand, PHC activity based on community participation was started in 1985, with the following three items as main themes: (1) Training of Village Health Volunteers (VHV) and Village Health Communicators (VHC), and development of their activities. (2) Establishment and operation of Health Centers. (3) Establishment and operation of Drug Cooperative System (DC). Earlier, as one of PHC activities developed by Japan, "Thailand Local Health Activity Improvement Project" based on the program of Thailand-Japan Partnership was initiated in 1976 in rural areas of Chanthaburi Prefecture. From 1982, third country training programs have been carried out by Japan International Cooperation Agency (JICA). Since 10 years have elapsed the initiation of PHC activity in rural areas in Thailand under the cooperation of the Governments of Thailand and Japan, it seems to be time to reconsider and study again how PHC activity should be developed in future based on candid evaluation of achievements and results.     

Correlates of maximal oxygen consumption during treadmill exercise

According to the Balke treadmill protocol, 39 healthy male USAF volunteers were subjected to maximal exercise. The subjects as a group passed the anaerobic threshold by the end of exercise since average venous lactate concentrations increased from 11.2 +/- 1.6 mg% (95% confidence limits) to 93.0 +/- 8.5 mg% (95% confidence limits), and the average gas exchange ratio (R) at the end of the exercise was greater than unity (p less than 0.0005). Tests for correlations showed weak but statistically significant (p less than 0.05) relationships between change in venous lactic acid concentrations and R (r = 0.44) and maximal heart rate (r = 0.34). Maximal oxygen consumption was correlated with time of exercise (r = 0.70) and subject weight (r = 0.33). Subject age and initial plasma lactate concentrations were not significantly correlated with any other variables. Multiple linear regression yielded an equation for prediction of maximal oxygen consumption which included terms for time of exercise and subject weight. Although the multiple correlation coefficent (r = 0.75) was statistically significant (p less than 0.05), it was considered insufficient for accurate prediction of maximal oxygen consumption.     

Gender comparison of peak oxygen uptake: repetitive box lifting versus treadmill running

The gender differences in peak oxygen uptake (VO2peak) for various modes of exercise have been examined previously; however, no direct gender comparisons have been made during repetitive lifting (RL). In the present study the VO2peak between RL and treadmill running (TR) was compared between 20 men [mean (SD) age, height, body mass and body fat: 21 (3) years, 1.79 (0.06) m, 81 (9) kg, 19 (6)%, respectively] and 20 women [mean (SD) age, height, body mass and body fat: 21 (3) years, 1.63 (0.05) m, 60 (7) kg, 27 (6)%, respectively]. VO2peak (l x min[-1]), defined as the highest value obtained during exercise to volitional fatigue, was determined using discontinuous protocols with treadmill grade or box mass incremented to increase exercise intensity. For RL VO2peak, a pneumatically driven shelf was used to lower a loaded box to the floor, and subjects then lifted the box, at a rate of 15 lifts x min(-1). VO2peak (l x min(-1) and ml x kg(-1) x min[-1]) and minute ventilation (VE, l x min[-1]) were determined using an on-line gas analysis system. A two-way repeated measures analysis of variance revealed significant gender effects, with men having higher values for VO2peak (l x min(-1) and ml x kg(-1) x min[-1]) and VE, but women having higher values of the ventilatory equivalent for oxygen (VE/VO2). There were also mode of exercise effects, with TR values being higher for VO2peak (l x min(-1) and ml x kg(-1) x min[-1]) and VE and an interaction effect for VO2peak (l x min(-1) and ml x kg(-1) x min[-1]) and VE/VO2. The women obtained a greater percentage (approximately 84%) of their TR VO2peak during RL than did the men (approximately 79%). There was a marginal tendency for women to decrease and men to increase their VE/VO2 when comparing TR with RL. The magnitude of the gender differences between the two exercise modalities appeared to be similar for heart rate, VE and R, but differed for VO2peak (l x min(-1) and ml x kg(-1) x min[-1]). Lifting to an absolute height (1.32 m for the RL protocol) may present a different physical challenge to men and women with respect to the degree of involvement of the muscle groups used during lifting and ventilation.     

Augmented upper body contribution to oxygen uptake during upper body exercise with concurrent leg functional electrical stimulation in persons with spinal cord injury

The purpose of this pilot study was to compare the contribution of upper body musculature to VO2 with and without concurrent leg FES (LFES). Eight subjects with spinal cord injury, lesion levels range C6-T12, performed upper body exercise (UBE) during no LFES (NOS), LFES at 40 mA (LOS), and 80 mA (HIS), at rest, 60% and 80% of VO2peak. Resting VO2 values were obtained during NOS, LOS and HIS conditions and were then subtracted from their respective whole body VO2 values to give an estimate of upper body VO2. Small and non significant increases were found in the HIS vs NOS condition at 60% VO2peak. Larger differences of 7.8% were found in the HIS vs NOS condition at 80% VO2peak (11.35+/-3.8 ml kg(-1) min(-1) to 12.24+/-4.0 ml kg(-1) min(-1)), although this too was not significant, perhaps due to the small number of subjects in this study and the consequently low statistical power to detect a significant difference. We discuss the implications for these preliminary results in the context of the existing literature on this topic.     

Energy expenditure of a noncontact boxing training session compared with submaximal treadmill running

The aim of this study was to determine the energy expenditure of a 1-h noncontact boxing training session and to compare these results with the energy expenditure of a more conventional recreational activity such as running. Eight healthy males, accustomed to noncontact boxing training, were recruited for the study. Subjects underwent three tests: (i) a boxing training session in the laboratory during which energy expenditure was measured continuously using indirect calorimetry (BOXL), (ii) a boxing training session in a boxing studio during which heart rate was measured continuously (BOXS), and (iii) an incremental running test on the treadmill during which energy expenditure was measured continuously. The energy expenditure during 60 min of BOXL ranged between 2519 and 3079 kJ (2821 +/- 190 kJ). Seven of the 8 subjects had higher heart rates during BOXL compared with those during BOXS, suggesting that the subjects exercised at a slightly higher intensity during BOXL, possibly because of the "one on one" supervision. A typical boxing training session lasting 60 min causes a person to expend 2821 +/- 190 kJ x h(-1), the same amount of energy as someone running about 9 km in 60 min on the treadmill.     

Scaling of the limb long bones to body mass in terrestrial mammals

In their normal state, RPE cell are strongly adherent to Bruch's membrane. Certain pathological conditions such as retinal detachment cause an injury-type response (probably augmented or induced by the local accumulation of a variety of substances which modulate cell behaviour) in which RPE begin to dissociate from the membrane. This RPE-Bruch's membrane separation may be mediated by proteins with counter-adhesive properties and proteolytic enzymes, partly derived from the RPE themselves. Concomitant with the RPE disassociation, the cells begin to lose tertiary differentiation characteristics and gain macrophage-like features. When the "free" RPE arrive at the surface of the neuroretina, they may attach to or create a provisional matrix. Some of the cells adopt a fibroblast-like phenotype. This phenotype is similar to that of the dermal fibroblast during cutaneous wound repair and the fibroblastic RPE synthesise the types of matrix components found in healing skin wounds. Many of these molecules in turn further modulate the activities of the cells via several families of cell surface receptors, while the RPE continue to remodel the new matrix with a range of proteolytic enzymes. The resulting tissue (or membrane) has many of the features of a contractile scar and is the hallmark of the condition known as proliferative vitreoretinopathy (PVR). Thus the development of PVR, and the resulting tractional distortion of the neuroretina, appears to be dependent on RPE-matrix interactions. The interactions present a number of potential therapeutic targets for the management of the disorder.     

O2 extraction maintains O2 uptake during submaximal exercise with beta-adrenergic blockade at 4,300 m

Whole body O2 uptake (VO2) during maximal and submaximal exercise has been shown to be preserved in the setting of beta-adrenergic blockade at high altitude, despite marked reductions in heart rate during exercise. An increase in stroke volume at high altitude has been suggested as the mechanism that preserves systemic O2 delivery (blood flow x arterial O2 content) and thereby maintains VO2 at sea-level values. To test this hypothesis, we studied the effects of nonselective beta-adrenergic blockade on submaximal exercise performance in 11 normal men (26 +/- 1 yr) at sea level and on arrival and after 21 days at 4,300 m. Six subjects received propranolol (240 mg/day), and five subjects received placebo. At sea level, during submaximal exercise, cardiac output and O2 delivery were significantly lower in propranolol- than in placebo-treated subjects. Increases in stroke volume and O2 extraction were responsible for the maintenance of VO2. At 4,300 m, beta-adrenergic blockade had no significant effect on VO2, ventilation, alveolar PO2, and arterial blood gases during submaximal exercise. Despite increases in stroke volume, cardiac output and thereby O2 delivery were still reduced in propranolol-treated subjects compared with subjects treated with placebo. Further reductions in already low levels of mixed venous O2 saturation were responsible for the maintenance of VO2 on arrival and after 21 days at 4,300 m in propranolol-treated subjects. Despite similar workloads and VO2, propranolol-treated subjects exercised at greater perceived intensity than subjects given placebo at 4,300 m. The values for mixed venous O2 saturation during submaximal exercise in propranolol-treated subjects at 4,300 m approached those reported at simulated altitudes >8,000 m. Thus beta-adrenergic blockade at 4,300 m results in significant reduction in O2 delivery during submaximal exercise due to incomplete compensation by stroke volume for the reduction in exercise heart rate. Total body VO2 is maintained at a constant level by an interaction between mixed venous O2 saturation, the arterial O2-carrying capacity, and hemodynamics during exercise with acute and chronic hypoxia.     

Maximal oxygen uptake during exercise with various combinations of arm and leg work

Oxygen uptake (VO2) was determined in 10 males during the following types of maximal exercise (work time: about 5 min): uphill running, bicycling, arm work (cranking), and combined arm work and bicycling (A + L). The A + L exercise was performed in four different ways, the arms doing 10%, 20%, 30%, or 40% of the same total rate of work; and also with the maximal bicycle work load plus either maximal or submaximal arm work. VO2 was the same in running as in all types of A + L exercise, except when the arm work load was 10% and 40% of the total rate of work, where VO2 was 2.5% (P less than 0.05) and 9.4% (P less than 0.001) lower, respectively. Bicycle VO2 was lower than VO2 in running but equal to A + L VO2 when arm work intensity was 40% of the total rate of work. It is concluded that VO2 during maximal exercise a) to a certain extent depends on the exercising muscle mass, b) is lower than the oxygen-consuming potential of the muscles involved in A + L exercise, and c) in A + L exercise is influenced by the ratio of arm work to total rate of work and the subject's fitness for arm work and bicycling.     

Fraction of carbon-free body mass as oxygen is a constant body composition ratio in men

Although elements are the foundation of the human body, information concerning the atomic level of body composition is still limited. The aim of this study was to explore potentially constant relationships among elements found in vivo. Based on the known stoichiometries of relevant chemical components, a theoretical model was derived, suggesting the existence of a relatively constant ratio of total body oxygen to carbon-free body mass (TBO/CFM) in men. Eight elements (C, H, N, Ca, P, K, Na and Cl ) were measured in 22 healthy male subjects by using in vivo neutron activation-40K whole-body counting, and TBO was calculated as the difference between body mass and the sum of the eight measured elements. TBO (in kg) was significantly correlated with CFM (in kg): TBO = 0.829 x CFM - 1.8; r = 0.998, P < 0.001, standard error of estimate = 0.4 kg. The ratio of TBO to CFM was relatively constant, mean +/- SD at 0. 800 +/- 0.009 with a CV of 1.1%. Oxygen and carbon are the two most abundant elements in the human body. The discovery of a constant relationship between oxygen and carbon is not only helpful for understanding the atomic level of body composition, but also provides the possibility of estimating the content of specific elements in vivo.     

Validity of oxygen uptake measurements during exercise under moderate hyperoxia

PURPOSE: The validity of oxygen uptake in hyperoxia (FIO2 = 30%) measured by an automated system (MedGraphics, CPX/D system) was assessed during the simulation of gas exchanges during exercise with a mechanical system and during submaximal exercise by human subjects. METHODS: The simulation system reproduced a stable and accurate VO2 for 30 min (sim-test). This trial was repeated nine times in normoxia and nine times in hyperoxia. Ten subjects also performed two submaximal exercises (55% of normoxic VO2max) on a cycle ergometer at the same absolute power in normoxia and in hyperoxia (ex-test). RESULTS: There was a significant downward drift of the oxygen fraction measurement in hyperoxia (< or = 0.10% for FIO2 and FEO2) during sim-test, but VO2 measurement remained stable in the two conditions. There was also a downward drift of the oxygen fraction measurement in the two conditions (< or = 0.07% for FIO2) during ex-test. VO2 was significantly higher in hyperoxia (+4.6%), and this result was confirmed using a modified Douglas bag method. CONCLUSIONS: These findings show that the CPX/D system is stable and valid for assessing VO2 in moderate hyperoxia.     

The effect of sedation on oxygen uptake during spontaneous breathing

Sedation may be used in intensive care and emergency medicine to improve the oxygen demand/delivery ratio. The influence of sedation has most frequently been investigated in a dose-related manner. The aim of the present study was to determine the effect-related influence of different sedatives on oxygen uptake (VO2) in relation to defined resting conditions. METHODS. Forty ASA I patients who had to undergo a minor surgical procedure were investigated 1.5 h before surgery at basal energy-expenditure measurement conditions. One of the following substances was given with a preset bolus rate in a double-blind, randomised order until a defined level of sleep or side effects was encountered: propofol (n = 8), midazolam (n = 8), thiopentone (n = 8), sodium chloride (n = 8), and fentanyl (n = 8). The sleep level was defined as sluggish response to a loud voice or tapping on the forearm. The variables VO2, carbon dioxide elimination (VCO2), end tidal CO2 (p(et)CO2), oxygen saturation (SaO2), heart rate, systemic blood pressure, skin temperature, and skin resistance on the sole of the foot were documented on-line on a computer. All variables were compared using differences of averages from 10-min periods before and after sedation during which the VO2 was minimal. RESULTS. The mean VO2 before sedation was 264 +/- 60 ml/min, and the measured energy expenditure did differ by -0.2% (+/- 14%) from mean predicted values using the Harris-Benedict equation. The VO2 was reduced by 15 +/- 2% with propofol, by 12 +/- 8% with midazolam, and by 10 +/- 5% with thiopentone. This was statistically significant compared to placebo treatment, as was the difference between propofol and thiopentone effects. All patients in these groups reached the defined sleep level, which was not achieved by the placebo and fentanyl groups. Placebo treatment changed the VO2 by 0.1% (+/- 2%). Fentanyl increased the VO2 by 5% (+/- 8%), which did not reach significance. In the fentanyl group the bolus application had to be stopped at a p(et)CO2 of 50 mm Hg in all patients. In the propofol, midazolam, and thiopentone groups the phasic changes of skin resistance were reduced to zero and the skin temperature increased from 27 +/- 2 degrees C to 32 +/- 2 degrees C. The fentanyl group showed an increase in changes of skin resistance without changes in temperature. CONCLUSIONS. Sleep induced by propofol, midazolam, or thiopentone to a clinically maximal desirable level in spontaneously breathing patients reduced VO2 by 10% to 15%. This level of sedation did not induce a relevant change in P(et)CO2 or SaO2. The effect of propofol appeared to be the most pronounced and least variable. This may be attributable to a more pronounced reduction in single-organ VO2 or to an undetected difference in level of sedation. Fentanyl did, in contrast to most publications on opioid effects, seem to increase VO2. Underlying mechanisms may be sought in an increased rate-pressure product and sympathetic activity on the basis of hypercapnia and changes in muscle tension.     

Prediction of maximum oxygen uptake during physical exercise on bicycle ergometer

Possibilities to predict maximum oxygen uptake (VO2max) during exercising on bicycle ergometer using the Russian Rating Perceived Exertion (RPE) was studied. Results of examination of 13 athletes demonstrate the possibility of predicting individual and group average VO2max on the basis of data from submaximum testing and the empirical formulas from the value of VO2max registered at RPE numbers 13 and 15. These VO2max values can serve as markers for assessing the dynamics of physical performance.     

Physiological and biomechanical responses during treadmill walking with graded loads

Eleven healthy men [mean (SD) for age, height, body mass and maximum oxygen consumption: 25.1 (3.0) years, 1.79 (0.06) m, 78.2 (10.5) kg and 56.9 (7.1) ml x kg(-1) x min(-1), respectively) completed two treadmill walking tests at their self-selected velocity while bilaterally carrying 15-kg and 20-kg loads (in a boxed container) for 4 min in front of the body. Each handle of the boxed container was fitted with a load cell so as to allow quantification of the load supported by each hand during load carriage. During the tests, oxygen uptake (VO2), heart rate (HR), and blood pressure (BP) were monitored using standardized procedures, and cardiac output (Qc) was measured using the carbon dioxide rebreathing method. Stroke volume (SV), arterio-venous oxygen difference (C(a-v)O2), rate pressure product (RPP) and total peripheral resistance (TPR) were calculated from the above measurements. The results showed that the two extremities sustained approximately 60% to 70% of the total load, with the balance being supported by the body. Significant increases (P < 0.05) in VO2, HR, Qc, and mean BP were observed during both of the load carriage walks compared to unloaded walking. However, SV, C(a-v)O2, RPP and TPR were unchanged (P > 0.05) during load carriage. Although VO2 was significantly higher during the 20-kg load carriage walk, no significant differences were observed between the two loads for any of the cardiovascular responses monitored. Contrary to our hypothesis, these results suggest that increasing the load from 15 kg to 20 kg during treadmill walking does not significantly increase the cardiovascular stress that occurs in healthy subjects.     

Dependency of standardized uptake values of fluorine-18 fluorodeoxyglucose on body size: comparison of body surface area correction and lean body mass correction

In an attempt to minimize dependency of conventional standardized uptake values (SUVs) of F-18-fluorodeoxyglucose (FDG) normalized for the total body weight (TBW) on patient's body weight, the uses of SUV corrected for the lean body mass (LBM) and that corrected for the body surface area (BSA) have been proposed as alternatives. We compared the dependency of SUVLBM and SUVBSA on the overall body size. FDG-PET images were acquired on 44 patients. SUVLBM and SUVBSA for the liver were determined as previously described. Following normalization of the scales of the values obtained from these two approaches, the mean +/- S.D. was 2.86 +/- 0.52 (SUVLBM) and 2.86 +/- 0.50 (SUVBSA). A linear regression analysis was performed for correlating the liver SUVLBM and SUVBSA, with each of TBW, LBM, BSA and height. The dependency of the two values on TBW was similar. SUVLBM showed a moderate dependency on height (r = 0.56, P = 0.00007), LBM (r = 0.55, P = 0.0001) and BSA (r = 0.51, P = 0.0004), whereas SUVBSA showed no dependency on LBM (r = 0.18, P = 0.24) or height (r = 0.20, P = 0.19), and a minimal dependency on BSA (r = 0.38, P = 0.01). In conclusion, SUVBSA appears to be less dependent on overall body size, particularly height and lean body mass, than SUVLBM.     

Autonomic control of cardiovascular performance and whole body O2 delivery and utilization in swine during treadmill exercise

OBJECTIVE: The present study determined the role of the autonomic nervous system (ANS) in the regulation of systemic and pulmonary circulation and of O2 delivery and utilization in swine at rest and during graded treadmill exercise. METHODS: Instrumented swine (n = 12) were subjected to treadmill exercise (1-5 km/h) under control conditions and in the presence of single and combined beta-adrenergic, alpha-adrenergic and muscarinic (M) receptor blockade. RESULTS: Exercise produced a four-fold increase in body O2 consumption, due to a doubling of both cardiac output and the arterio-mixed-venous O2 content difference. The latter resulted from an increase in O2 extraction, from 45 +/- 1% at rest to 74 +/- 1% at 5 km/h, as the O2 carrying capacity [haemoglobin concentration (Hb)] increased by only approximately 10%. The increase in cardiac output resulted from a doubling of the heart rate and a small (< 10%) increase in stroke volume. The mean aortic pressure (MAP) was unchanged, implying a 50% decrease in systemic vascular resistance (P < or = 0.05). In contrast, exercise had no significant effect on pulmonary vascular resistance. The sympathetic division of the ANS controlled O2 delivery via beta-adrenoceptors (heart rate and contractility) and Hb concentration via alpha-adrenoceptor-mediated splenic contraction. In addition, the sympathetic division modulated systemic vascular tone via alpha- and beta-adrenoceptors, but also exerted a vasodilator influence on the pulmonary circulation via beta-adrenoceptors. The parasympathetic division controlled O2 delivery in part directly (heart rate) and in part indirectly via inhibition of beta-adrenoceptor activity (heart rate and contractility), even during heavy exercise. In addition, the parasympathetic division exerted a direct vasodilator influence on the pulmonary, but not on the systemic, circulation. CONCLUSIONS: Thus, in swine, in a manner similar to that in humans, both the sympathetic and parasympathetic division of the ANS contribute to cardiovascular homeostasis during exercise up to levels of high intensity.     

Plantar foot pressures during treadmill walking with high-heel and low-heel shoes

The effect of walking with high-heel shoes on plantar foot pressure distribution was investigated. Ten normal women walking in shoes with low heels were compared to women walking in high-heel shoes. It was shown that high-heel shoes increased the load on the forefoot and relieved it on the hindfoot. The load passed toward the medial forefoot and the hallux. The lateral side of the forefoot showed a decrease in contact area, reduced forces, and peak pressures. The medial side of the forefoot had a higher force-time and pressure-time integral. It is suggested that these higher loads on the medial forefoot may aggravate symptoms in patients with hallux valgus deformity.     

Relationship of premorbid mass and energy intake to increase of body mass during the treatment of anorexia nervosa

We studied 152 healthy pregnant women and their 156 newborns for markers of hepatitis B virus (HBV) infection in Dakar, Senegal. Of these, 120 mothers (79%) had antibodies to the hepatitis B core antigen (anti-HBc), 21 (13.8%) were hepatitis B surface antigen (HBs Ag) positive, including 2/21 (9.5%) hepatitis B core-associated antigen (HBe Ag) positive and 1/21 (4.7%) HBV DNA positive. At birth, 11 (7%) infants were HBs Ag positive; 9/11 had an HBs Ag positive mother. Ten of these HBs Ag positive-born infants were investigated at 6-7 months: 5 were strongly HBs Ag positive and developed antibodies to HBs Ag, HBc Ag or HBe Ag; these 5 (3.2% of the total) probably became chronic carriers of HBV. The 5 others were HBs Ag negative and 4/5 did not develop antibodies against HBV Ag; HBs Ag positivity at birth was likely due to contamination of the mother's blood. Thirty-one of the 145 HBs Ag negative-born infants were studied at 6-7 months and remained HBs Ag negative. However, 5 (16%) showed evidence of HBV infection occurring between 0 and 6 months, as shown by the development of antibodies to HBs Ag, HBc Ag, and/or HBe Ag. Despite the low prevalence of HBV DNA and HBe Ag in HBs Ag positive African mothers, this study shows the occurrence of perinatal transmission of HBV in West Africa, in contrast with previous studies. Perinatal HBV transmission could explain the HBV vaccination failure recently reported in children in Senegal.     

Blood pressure and body mass index of hypertensive patients before and during the medication

Machinable bioactive glass ceramics (MBGC) has been employed in maxillofacial augmentation as a substitute for bone grafts in 36 patients with satisfactory results. Two years' follow-up did not show inflammatory reaction and rejection of the implant. Clinical applications of MBGC proved its reliability.     

Biomechanical analysis of body mass transfer during stair ascent and descent of healthy subjects

The purposes of this study were to: 1) assess whole body center of mass (CM) motion in the frontal, sagittal, and transverse planes; 2) compare CM displacement with center of pressure (CP); and, 3) further define the stance and swing subphases of stair ascent (SA) and stair descent (SD) based on critical CM, CP, and ground reaction force (GRF) events. SA and SD were analyzed on a convenience sample of 11 subjects. Unpaced data were collected from 28 SA trials and 24 SD trials utilizing a bilateral SELSPOT II/TRACK data acquisition system and two Kistler force plates at a sampling frequency of 153 Hz. Twenty-six discrete data points were chosen from each trial for analysis. Each identified point detailed the intersection, separation, maximum or minimum value of CM, CP, or GRF in all three planes. Specific phases of SA and SD are presented and described. The actions of CM, CP, and GRF are presented during each phase. Results further refine the phases originally described by McFayden and Winter. Subtle differences in phases and duration of single and double support are demonstrated between SA and SD. Based on these results, it is apparent that SD is a more dynamic process with greater inherent instability. Knowledge of SA and SD phases and CM/CP dynamics in healthy, normal subjects will permit comparison with patients exhibiting various pathologies. Such comparison should facilitate the development of appropriate intervention strategies.     

Changes in maximum oxygen uptake during prolonged training, overtraining, and detraining in horses

Thirteen standardbred horses were trained as follows: phase 1 (endurance training, 7 wk), phase 2 (high-intensity training, 9 wk), phase 3 (overload training, 18 wk), and phase 4 (detraining, 12 wk). In phase 3, the horses were divided into two groups: overload training (OLT) and control (C). The OLT group exercised at greater intensities, frequencies, and durations than group C. Overtraining occurred after 31 wk of training and was defined as a significant decrease in treadmill run time in response to a standardized exercise test. In the OLT group, there was a significant decrease in body weight (P < 0.05). From pretraining values of 117 +/- 2 (SE) ml.kg-1.min-1, maximal O2 uptake (VO2max) increased by 15% at the end of phase 1, and when signs of overtraining were first seen in the OLT group, VO2max was 29% higher (151 +/- 2 ml.kg-1.min-1 in both C and OLT groups) than pretraining values. There was no significant reduction in VO2max until after 6 wk detraining when VO2max was 137 +/- 2 ml.kg-1.min-1. By 12 wk detraining, mean VO2max was 134 +/- 2 ml.kg-1.min-1, still 15% above pretraining values. When overtraining developed, VO2max was not different between C and OLT groups, but maximal values for CO2 production (147 vs. 159 ml.kg-1.min-1) and respiratory exchange ratio (1.04 vs. 1.11) were lower in the OLT group. Overtraining was not associated with a decrease in VO2max and, after prolonged training, decreases in VO2max occurred slowly during detraining.