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Biomedical subjects

G C Gass

Publications and source records attributed to G C Gass.

At least 19 recordsLinked to original sources
PubMed1995

Maximal physiological responses during arm cranking and treadmill wheelchair propulsion in T4-T6 paraplegic men.

The aim of the study was to compare the exercise responses during maximum wheelchair propulsion on a motor driven treadmill (TM) and maximum arm cranking (AC) in a homogenous group of nine paraplegic men with clinically complete spinal cord lesions between T4 and T6. The test order for each ergometer was random and time between the two ergometer tests was 3-7 days. All experiments were conducted in an air conditioned environment (23 degrees C DB, 18 degrees C WB). The highest VO2 recorded during the final minute of arm cranking (1.65 +/- 0.14 l min-1) and wheelchair propulsion on the treadmill (1.72 +/- 0.10 l min-1) was not significantly different. There were no significant differences in heart rate during the final minute of arm cranking (177 +/- 3 b min-1), and wheelchair propulsion on a motor driven treadmill (177 +/- 4 b min-1), nor were there any significant differences in minute ventilation (STPD) between AC (52 +/- 6.6 l min-1) and TM (56.1 +/- 4.8 l min-1). The VCO2 l min-1 for AC (2.00 +/- 0.20 l min-1) and TM (2.00 +/- 0.12 l min-1) was also not significantly different. The present study found that, unlike previous studies, no significant differences in VO2 (l min-1, ml kg-1 min-1) VE (l min-1), VCO2 (l min-1) or heart rate (b min-1) were found between the two modes of ergometry during the last minute of incremental exercise to exhaustion in a homogenous group of T4-T6 paraplegic men.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

The effects of sauna on tetraplegic and paraplegic subjects.

Six tetraplegic (T) and 4 paraplegic (P) subjects underwent a 20-minute pre sauna phase (30 degrees C DB; 65% RH), and an up to 15-minute sauna (85 degrees C DB; less than 10% RH), followed by a 15 minute post sauna phase (30 degrees C DB; 65% RH). During all phases subjects wore a bathing suit and remained supine on a hospital trolley. Heart rate (HR) and blood pressure (BP) were recorded during all phases. Rectal temperature (Trec) was measured by a probe (AD590) inserted approximately 14 cm into the rectum. Oral temperature (Toral) also utilising (AD590) circuitry was recorded simultaneously with Trec. Skin temperature (Tsk) (AD590) was measured on the head, chest, right thigh and right calf. Forehead sweat rate (SR) was determined from dew point temperature (Tdp). A catheter was inserted into a dorsal hand or foot vein and venous blood was withdrawn at selected times and analysed for haemoglobin (Hb) and haematocrit (Hct), and the separated plasma was analysed for glucose (Glu), sodium (Na+), potassium (K+) and chloride (C1-). Venous blood sampled just prior to entering and just prior to leaving the sauna, was analysed for adrenalin (A) and noradrenalin (NA) using high performance liquid chromatography. For both groups HR rose significantly during the sauna with a significant decline in HR for the P group during the post sauna phase. There were no significant changes in systolic BP for either group. A significant decline in diastolic BP was found for the T group during the post sauna phase. There were no episodes of syncope.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Pressure↗
PubMed1991

Effects of prolonged exercise at a similar percentage of maximal oxygen consumption in trained and untrained subjects.

Six trained male cyclists and six untrained but physically active men participated in this study to test the hypothesis that the use of percentage maximal oxygen consumption (%VO2max) as a normalising independent variable is valid despite significant differences in the absolute VO2max of trained and untrained subjects. The subjects underwent an exercise test to exhaustion on a cycle ergometer to determine VO2max and lactate threshold. The subjects were grouped as trained (T) if their VO2max exceeded 60 ml.kg-1.min-1, and untrained (UT) if their VO2max was less than 50 ml.kg-1.min-1. The subjects were required to exercise on the ergometer for up to 40 min at power outputs that corresponded to approximately 50% and 70% VO2max. The allocation of each exercise session (50% or 70% VO2max) was random and each session was separated by at least 5 days. During these tests venous blood was taken 10 min before exercise (- 10 min), just prior to the commencement of exercise (0 min), after 20 min of exercise (20 min), at the end of exercise and 10 min postexercise (+ 10 min) and analysed for concentrations of cortisol, [Na+], [K+], [Cl-], glucose, free fatty acid, lactate [la-], [NH3], haemoglobin [Hb] and for packed cell volume. The oxygen consumption (VO2) and related variables were measured at two time intervals (14-15 and 34-35 min) during the prolonged exercise tests. Rectal temperature was measured throughout both exercise sessions. There was a significant interaction effect between the level of training and exercise time at 50% VO2max for heart rate (fc) and venous [la-].(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

The relationship between the ventilation and lactate thresholds following normal, low and high carbohydrate diets.

Five men performed an incremental exercise test following a normal, low and high carbohydrate dietary regimen over a 7-day period, to examine the influence of an altered carbohydrate energy intake on the relationship between the ventilation (VET) and lactate (LaT) thresholds. VET and LaT were determined from the ventilatory equivalents for O2 (VE.VO2(-1) and CO2 (VE.VCO2(-1) and the log-log transformation of the lactate (La) to power output relationship, respectively. The total duration of the incremental exercise test, carbon dioxide output (VCO2), respiratory exchange ratio, blood La values and arterialized venous partial pressure of CO2 (PCO2) were reduced, and VE.VCO2(-1), the slope of the VE-VCO2 relationship, blood beta-hydroxybutyrate and pH were increased during the low carbohydrate trial compared with the other conditions. Total plasma protein and Na+, K+, and Cl- were similar across conditions. LaT and VET were unaffected by the altered proportions of carbohydrate in the diets and occurred at a similar oxygen consumption (mean VO2 across trials was 1.98 L.min-1 for VET and 2.01 L.min-1 for LaT). A significant relationship (r = 0.86) was observed for the VO2 that represented individual VET and LaT values. The increased VE.VCO2(-1) and slope of the VE-VCO2 relationship could be accounted for by the lower PCO2. It is concluded that alterations in carbohydrate energy intake do not produce an uncoupling of VET and LaT as has been reported previously.

Adult↗
PubMed1989

Metabolic and cardiorespiratory responses relative to the anaerobic threshold.

The present study has compared the metabolic and cardiorespiratory responses for two groups of male subjects during 20 min of exercise at the anaerobic threshold (AT), at AT + 1/3, and at AT + 2/3 of the difference (delta) between AT and VO2max. A log-log transformation of the lactate (LA)-power output relationship was used to define AT and divide subjects into a high (N = 7, AT = 51.9 +/- 1.5% VO2max) and low (N = 5; AT = 41.9 +/- 1.8% VO2max) AT group. No differences were observed between groups during exercise at AT for VE.VO2-(1), VE.VCO2(-1), pH, pCO2, blood LA, and plasma strong ions Na+, K+, and Cl-. Although blood LA values were significantly elevated for the low AT subjects (2.3 +/- 0.6 mmol.l-1) compared with the high AT group (1.0 +/- 0.1 mmol.l-1) during exercise at AT + 1/3 delta, no other differences between groups were noted. In contrast, marked differences were observed between groups during exercise at AT + 2/3 delta. The high AT group showed no change in VE (79.1 +/- 4.8 l.min-1), pH (7.367 +/- 0.01), pCO2 (37.3 +/- 1.2 mm Hg), and blood LA (2.9 +/- 0.3 mmol.l-1) during the final 10 min of the 20 min exercise test.(ABSTRACT TRUNCATED AT 250 WORDS)

Acid-Base Equilibrium↗
PubMed1988

Rectal and rectal vs. esophageal temperatures in paraplegic men during prolonged exercise.

This study investigated the rectal (Tre), esophageal (Tes), and skin (Tsk) temperature changes in a group of trained traumatic paraplegic men pushing their own wheelchairs on a motor-driven treadmill for a prolonged period in a neutral environment. There were two experiments. The first experiment (Tre and Tsk) involved a homogeneous group (T10-T12/L3) of highly trained paraplegic men [maximum O2 uptake (VO2max) 47.5 +/- 1.8 ml.kg-1.min-1] exercising for 80 min at 60-65% VO2max.Tre and Tsk (head, arm, thigh, and calf) and heart rate (HR) were recorded throughout. O2 uptake (VO2), minute ventilation (VE), CO2 production (VCO2), and heart rate (HR) were recorded at four intervals. During experiment 1 significant changes in HR and insignificant changes in VCO2, VE, and VO2 occurred throughout prolonged exercise. Tre increased significantly from 37.1 +/- 0.1 degrees C (rest) to 37.8 +/- 0.1 degrees C after 80 min of exercise. There were only significant changes in arm Tsk. Experiment 2 involved a nonhomogeneous group (T5-T10/T11) of active paraplegics (VO2max 39.9 +/- 4.3 ml.kg-1.min-1) exercising at 60-65% VO2max for up to 45 min on the treadmill while Tre and Tes were simultaneously recorded. Tes rose significantly faster than Tre during exercise (dT/dt 20 min: Tes 0.050 +/- 0.003 degrees C/min and Tre 0.019 +/- 0.005 degrees C/min), and Tes declined significantly faster than Tre at the end of exercise. Tes was significantly higher than Tre at the end of exercise. Our results suggest that during wheelchair propulsion by paraplegics, Tes may be a better estimate of core temperature than Tre.

Body Temperature↗
PubMed1987

A systems model approach to the ventilatory anaerobic threshold.

An analogue systems model of whole-body human bioenergetics predicts a change in kinetics of VO2 time series values as a result of exercise levels above an anaerobic threshold. Plotted VO2 results from exercising subjects appear to confirm this change. The purpose of this study is to describe the background to the systems model analogue of the anaerobic threshold and a test procedure devised to estimate this threshold. The estimate so obtained has the dual advantages of being based on model theory and of not being subject to the sort of ambient variations inherent in a single-test determination. A non-homogeneous group of eight subjects comprising a full replicate of a 2(3) factorial experimental design, with factors age, sex and training status, took part in the study. On one hand the results indicate acceptance of the systems model theory. On the other, the analogue threshold measure possesses corresponding properties to the conventional anaerobic threshold. It is higher for trained (155-214 W) than for untrained subjects (108-158 W), higher for males (149-214 W) than for females (108-170 W), and displays no evident interaction effects. Results for the VO2 time constant and for the work efficiency, display similar effects except for an interaction in the latter between age and training status. These experimental findings are regarded as confirmatory of the nature of the analogue threshold measure.

Adult↗
PubMed1987

Effects of prolonged exercise in highly trained traumatic paraplegic men.

This study investigated the cardiovascular and metabolic responses to prolonged wheelchair exercise in a group of highly trained, traumatic paraplegic men. Six endurance-trained subjects with spinal cord lesions from T10 to T12/L3 underwent a maximal incremental exercise test in which they propelled their own track wheelchairs on a motor-driven treadmill to exhaustion to determine maximal O2 uptake (VO2max) and related variables. One week later each subject exercised in the same wheelchair on a motorized treadmill at 60-65% of VO2max for 80 min in a thermoneutral environment (dry bulb 22 degrees C, wet bulb 17 degrees C). Approximately 10 ml of venous blood were withdrawn both 20 min and immediately before exercise (0 min), after 40 and 80 min of exercise, and 20 min postexercise. Venous blood was analyzed for hematocrit (Hct), hemoglobin (Hb), and lactate, and the separated plasma was analyzed for glucose, K+, Na+, Cl-, free fatty acid (FFA), and osmolality. VO2, CO2 production (VCO2), minute ventilation (VE), respiratory exchange ratio (R), net efficiency, and wheelchair strike rate were determined at four intervals throughout the exercise period. Data were analyzed with an analysis of variance repeated-measures design and a Scheffé post hoc test. VO2max was 47.5 +/- 1.8 (SE) ml.min-1.kg-1 with maximal VE BTPS and maximal heart rate (HR) being 100.1 +/- 3.8 l/min and 190 +/- 1 beats/min, respectively. During prolonged exercise there were no significant changes in VO2, VCO2, VE, R, net efficiency, wheelchair strike rate, and lactate, glucose, and Na+ concentrations. Significant increases occurred in HR, FFA, K+, Cl-, osmolality, Hb, and Hct throughout exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1984

Intermittent claudication. The effect of physical training on walking tolerance and venous lactate concentration.

Twenty-one patients with intermittent claudication underwent a physical exercise program lasting 8 weeks. The patients were classified on the basis of maximal walking tolerance (MWT) and diagnosis at the initial examination. Seven of the patients had a MWT less than 1,000 m and no symptoms of chronic obstructive airways disease (COAD) or angina (group A), seven had a MWT less than 1,000 m plus angina and/or COAD (group B) and seven had an unlimited (greater than 1,250 m) MWT (group C). At the completion of the training program all three groups showed a significant improvement in walking distance to pain and stress test capacity. During the post-training walking tolerance test, the venous lactate concentrations in group A were lower after 2 min and 4 min of exercise, and at exhaustion (P less than 0.05). Group A patients showed a significant correlation between an increase in MWT after training and a decrease in maximum lactate concentration measured during walking. Although the patients in group B had a significant increase in MWT, blood lactate concentrations in this group were not always decreased by physical training. Group C lactate concentrations were lower after 8 min, 15 min, and 30 min of walking (P less than 0.05). It is concluded that a physical training program increases walking tolerance in different categories of claudicants, and possible mechanisms for the improvement are discussed.

Aged↗
PubMed1984

The effect of a single sauna exposure on spermatozoa.

Semen was collected at weekly intervals for 3 wk before and 10 wk after the sauna exposure at 85 degrees C for 20 minutes. The numbers, morphology, ultrastructure, motility, viability and metabolism of the sperm was assessed. Sperm numbers fell within one wk and slowly returned to normal in 5 wk. The earliest ultrastructural change was swelling of the plasma membrane, followed by an increase in the number of immature forms and disorganization of the arrangement of the mitochondria. Motility, glucose utilization and lactic acid accumulation of the sperm rose temporarily immediately after sauna.

Glucose↗
PubMed1984

The maximum physiological responses during incremental wheelchair and arm cranking exercise in male paraplegics.

Ten physically active male paraplegics (means = 30 +/- 1 yr), with lesion levels ranging from T5 to L4/S2, underwent two incremental exercise tests to exhaustion. The exercise tests were arm cranking, utilizing an electronically-braked arm cranker, and wheelchair propulsion on a motor-driven treadmill. The subjects were randomly assigned to groups, and the exercise tests were separated by 1 wk. For the first six subjects, during both modes of exercise, VO2, VCO2, R, VE, and heart rates were recorded throughout; for the remaining four subjects the same variables were recorded after the heart rate reached 160 b X min-1. The VO2 (l X min-1 and ml X min-1 X kg-1), VCO2 (l X min-1), HR, and VE BTPS (l X min-1) were significantly higher at the termination of the wheelchair exercise than at the termination of the arm cranking exercise. The minute ventilation, when recorded throughout both exercise tests, showed a relatively linear phase at first, followed by a curvilinear phase. The findings of this study indicate that in the present group of paraplegics, the highest VO2 was obtained during maximum wheelchair exercise.

Adult↗
PubMed1983

Anaerobic threshold and lactate turnpoint.

Venous lactate concentration and ventilatory responses to progressively increased work rates were studied in 16 men who performed an incremental exercise test to exhaustion on an electrically braked cycle ergometer. In this test the characteristic curvilinear increase in venous lactate concentrations was observed. In addition to the anaerobic threshold (AT), a second breakpoint was observed and named the lactate turnpoint (LTP). Eight of the 16 subjects performed a second incremental exercise test initiated during lactic acidosis. In this test the direction of change in venous lactate concentrations was different. The work rate at which lactate concentrations again increased, after a steady decline (previously described as the AT2), was similar to the work rate established for the LTP in the first test. In the second test removal of lactate was demonstrated at work rates exceeding the AT. Although the lactate response to the two tests was different the pattern of change was similar, with the two breakpoints occurring at the same work rates. Collectively these results lend a measure of support to the hypothesis of a positive relationship between the AT, LTP, and a pattern of recruitment of motor units with different enzyme profiles. Both the AT and LTP were predictable from the ventilatory response to incremental exercise.

Acidosis↗
PubMed1983

Prolonged exercise in highly trained female endurance runners.

The effects of prolonged exercise in a 21 degree C dry bulb and 15 degree C wet bulb environment at 65%-70% VO2max were examined in seven highly trained females. The subjects, aged 22-35 years, underwent an initial incremental treadmill test to exhaustion, with assessment of VO2max and related cardiorespiratory variables. One week later, under similar environmental conditions, subjects ran at approximately 65% VO2max for 80 min on a motor-driven treadmill. Approximately 10 ml of venous blood was withdrawn 10 min prior and immediately prior to the onset of prolonged exercise, and at 20, 40, 60, and 80 min, and 20 min post-exercise. Venous blood was analyzed for glucose, lactate, osmolality, Na+, K+, protein, and hemoglobin (Hb). Hematocrit was measured and changes in plasma volume calculated. VO2, VE, respiratory exchange ratio, and heart rate were recorded at 17, 37, and 77 min. The percent body fat estimated from skinfold thicknesses was 19 +/- 1%. The mean VO2max was 59.3 +/- 1.0 ml . kg-1 . min-1, with a mean max VE STPD and heart rate of 78.75 +/- 3.10 1 . min-1 and 175 +/- 4 beats . min-1, respectively. No significant changes occurred in VO2, VE, % VO2max, heart rate, venous lactate, plasma glucose, or plasma protein during the prolonged exercise. A significant decrease in respiratory exchange ratio was noted. Significant changes also occurred in hematocrit, Hb, Na+, K+, and osmolality. An interesting finding was the pre-exercise expansion of the plasma volume.

Adipose Tissue↗
PubMed1981

Oxygen deficit during incremental exercise.

The oxygen deficit and debt have conventionally been determined during exercise at constant work rates. During this study these were calculated during and after exercise at progressively incremented work rates. Five men performed two successive incremental exercise tests to exhaustion on an electronically braked cycle ergometer. The two tests were separated by a 5 min rest period. The oxygen deficit was defined as the sum of the minute differences between the measured oxygen uptake and the oxygen uptake occurring during steady state work at that same rate. The oxygen deficit was quantified for the work periods before and after the anaerobic threshold (AT) as determined from respiratory gas analysis (ATR). The measured deficit for the period before the ATR was smaller than the deficit measured in the same subjects during steady state work at low intensity (below the ATR) and was also less than the rapid component of the oxygen repayment as determined after the second incremental test. It was concluded that this test could be used for the determination of anaerobic capacity as represented by the total oxygen deficit (within motivational limits), but that the lactacid and alactacid components of the deficit could not be differentiated. A considerable portion of the alactacid component of the deficit was incurred after the onset of the ATR.

Adolescent↗
PubMed1981

Serum cortisol response to incremental work in experienced and naive subjects.

Twelve experienced and seven naive male subjects with a similar Vo2max, performed an incremental work test on an electronically braked bicycle until exhaustion. High venous lactate concentrations were recorded in both groups (naive-11.74 +/- 2.43, experienced-13.96 +/- 2.36 mmol/liter). No significant relationship could be demonstrated between Vo2max, venous lactate concentration, Borg ratings of perceived exertion, and the serum cortisol response. The postexercise increase in serum cortisol was significant in both experienced (59%) and naive (138%) groups, and was significantly greater in the naive as compared to the experienced subjects. The present results indicate that the psychoendocrine response to a novel situation was a major determinant of the serum cortisol response to maximum work.

Humans↗
PubMed1981

Blood lactate concentration following maximum exercise in trained subjects.

The time when blood lactate reaches peak concentration following maximum exercise is unclear. The post exercise venous blood lactate concentration was determined serially for 30 minutes in 13 trained men following maximum exercise on a motor driven treadmill. Lactates were determined enzymatically in duplicate. The VO2 max and percent body fat was 65.1 +/- 4.8 ml.kg-1.min-1 and 11.4 +/- 1.4, respectively. The venous lactate reached a peak concentration at the 6th minute (14.2 mmol.L-1) of an inactive recovery, and declined linearly thereafter to reach a concentration of 7.43 +/- 0.60 mmol.L-1 at the 30th minute. The net rate of lactate removal was .30 mmol.L-1.min-1. Statistical analysis found no significant difference in lactate concentration during the 4th, 5th and 6th minute post exercise, indicating that these post exercise times may be appropriate to sample venous blood for peak lactate concentration.

Adult↗
PubMed1981

The effects of prolonged exercise on spinally injured subjects.

The effects of prolonged exercise on paraplegics have not been reported. Seven male paraplegic subjects with spinal lesions from T4 - T12 - L1 underwent an incremental wheelchair treadmill test to exhaustion. Heart rate (HR), VO2max, and VESTPD were recorded and calculated. One week later, subjects exercised in their wheelchairs at approximately 50% (mean = 52 +/- 2%) of VO2max for 60 min on a motorized treadmill. Approximately 10 ml venous blood was withdrawn both 10 min and immediately prior to the prolonged exercise, at 20, 40, and 60 min of the exercise period, and at 10 min post-exercise. Venous blood was analyzed for glucose, hemoglobin, lactate, Na+, K+, Cl-, and plasma protein. Hematocrit was recorded and plasma volume changes calculated VO2, VE, and HR were recorded at 17, 37, and 57 min of the prolonged exercise. The mean VO2max was 29.5 +/- 2.7 ml.kg-1.min-1, with a mean max VESTPD and HR of 61.86 +/- 4.98 1.min-1 and 174 +/- 4 b.min-1, respectively. The changes in VO2 and VE during the prolonged wheelchair exercise were not significant. Significant changes occurred in venous lactate and plasma glucose concentrations during prolonged wheelchair exercise. Plasma volume changes were similar to those seen in able-bodied subjects. A notable finding was the pre-exercise hemodilution. Present data indicate that paraplegics can exercise at approximately 50% VO2 for 60 min, producing responses similar to those in able-bodied subjects.

Adult↗