Ira Jacobs - Academia.edu (original) (raw)

Papers by Ira Jacobs

Research paper thumbnail of Energy Balance of Canadian Armed Forces Personnel during an Arctic-Like Field Training Exercise

Nutrients

Operating in temperature extremes frequently leads to a discrepancy in energy balance. Investigat... more Operating in temperature extremes frequently leads to a discrepancy in energy balance. Investigating the effects of operating in extreme cold temperatures on metabolic requirements has not been well described in Canadian Armed Forces (CAF) personnel. The objective was to accurately assess energy deficits using the “gold standard” methodology for measuring energy intake (EI) and energy expenditure (EE). Nutritional intake of a convenience sample of 10 CAF Class A Reservists, completing a basic military qualification (land) course under winter weather conditions, was assessed using the daily measured food intake/food waste collections. EE was measured by the doubly-labelled water method. Average EI was 2377 ± 1144 kcal/day, which was below the EE (4917 ± 693 kcal/day), despite having ~5685 kcal available in the field rations. A significant body weight loss of 2.7% was associated with the average daily energy deficit of 2539 ± 1396 kcal. As a result, participants demonstrated voluntary...

Research paper thumbnail of Comparison of dietary intakes of Canadian Armed Forces personnel consuming field rations in acute hot, cold, and temperate conditions with standardized infantry activities

Military Medical Research

Research paper thumbnail of The effects of exercise and ambient temperature on dietary intake, appetite sensation, and appetite regulating hormone concentrations

Research paper thumbnail of The Effects of Thermal Dehydration on Performance of the Wingate Anaerobic Test

International Journal of Sports Medicine

Research paper thumbnail of Energy Metabolism in Cold-Stressed Females: Implications for Predictive Modeling

Research paper thumbnail of Rate dependent influence of arterial desaturation on self-selected exercise intensity during cycling

PloS one, 2017

The purpose of this study was to clarify if Ratings of Perceived Exertion (RPE) and self-selected... more The purpose of this study was to clarify if Ratings of Perceived Exertion (RPE) and self-selected exercise intensity are sensitive not only to alterations in the absolute level of arterial saturation (SPO2) but also the rate of change in SPO2. Twelve healthy participants (31.6 ± 3.9 y, 175.5 ± 7.7 cm, 73.3 ± 10.3 kg, 51 ± 7 mL·kg-1·min-1 [Formula: see text]) exercised four times on a cycle ergometer, freely adjusting power output (PO) to maintain RPE at 5 on Borg's 10-point scale with no external feedback to indicate their exercise intensity. The fraction of inspired oxygen (FIO2) was reduced during three of those trials such that SPO2 decreased during exercise from starting values (>98%) to 70%. These trials were differentiated by the time over which the desaturation occurred: 3.9 ± 1.4 min, -8.7 ± 4.2%•min-1 (FAST), 11.0 ± 3.7 min, -2.8 ± 1.3%•min-1 (MED), and 19.5 ± 5.8 min, -1.5 ± 0.8%•min-1 (SLOW) (P < 0.001). Compared to stable PO throughout the control condition (no...

Research paper thumbnail of Modafinil Prolongs Time to Exhaustion During High Intensity Submaximal Exercise 224

Med Sci Sport Exercise, 1997

Research paper thumbnail of Blood Lactate: Its Use in the Evaluation of Exercise Performance and Training

Med Sci Sport Exercise, 1984

Research paper thumbnail of Blood Lactate: Implications for Training and Sports Performance

Sports Medicine, 1986

The blood lactate response to exercise has interested physiologists for over fifty years, but has... more The blood lactate response to exercise has interested physiologists for over fifty years, but has more recently become as routine a variable to measure in many exercise laboratories as is heart rate. This rising popularity is probably due to: the ease of sampling and improved accuracy afforded by recently developed micro-assay methods and/or automated lactate analysers; and the predictive and evaluative power associated with the lactate response to exercise. Several studies suggest that the strong relationship between exercise performance and lactate-related variables can be attributed to a reflection by lactate during exercise of not only the functional capacity of the central circulatory apparati to transport oxygen to exercising muscles, but also the peripheral capacity of the musculature to utilise this oxygen. For example, several studies contrast the relationship between VO2max and endurance running performance with that between a lactate variable and the same running performance. In every study, the lactate variable is more highly correlated with performance. Similarly, prescribing training intensity as a function of the lactate concentration elicited by the training may prove to be a means of obtaining a more homogeneous adaptation to training in a group of athletes or subjects than is obtained by setting intensity as a function of maximal heart rate or % VO2max. A review of the recent literature shows that the lactate response to supramaximal exercise is a sensitive indicator of adaptation to 'sprint training' and is correlated with supramaximal exercise performance. This review also describes the possible applications of lactate measurements to enhance the rate of recovery from high intensity exercise. Although the lactate response to exercise is reproducible under standardised conditions it can be influenced by the site of blood sampling, ambient temperature, changes in the body's acid-base balance prior to exercise, prior exercise, dietary manipulations, or pharmacological interpretation.

Research paper thumbnail of Perspectives on Retaining a DRDC Human Sciences Centre...in Toronto

Research paper thumbnail of Electro-mechanical response times and rate of force development in males and females

Medicine Amp Science in Sports Amp Exercise, Mar 1, 1986

Muscle force development is influenced by both central (pre-motor end plate) and peripheral (post... more Muscle force development is influenced by both central (pre-motor end plate) and peripheral (post-motor end plate) components. Conflicting results are available concerning gender-related differences in the central component. This study compared males and females with regard to the following electro-mechanical response variables: total reaction time, pre-motor time, electro-mechanical delay, and the rate of force development during a maximal voluntary isometric contraction (MVC) of the elbow flexors. Forty-six males and 40 females performed MVCs against a bar attached to a force transducer. Subjects were instructed to attempt to flex the elbow with maximal force as rapidly as possible after perceiving a visual stimulus. Surface electromyographic activity was recorded from the biceps brachii and was sampled simultaneously with the force transducer data at 2 kHz and stored digitally. For data analyses the subjects were separated into four groups based on the force generated during the MVC: weak females, weak males, strong females, and strong males. Neither total reaction time nor pre-motor time was significantly different across groups. The electro-mechanical delay for both male groups was significantly shorter than for both female groups. Electro-mechanical delay was weakly, but significantly, correlated with rate of force development and maximum force. During a single MVC the times required to attain 25, 50, 75, and 100% MVC were similar in all groups. The results suggest that at least part of the gender difference in maximum strength may be due to differences in electro-mechanical response times.

Research paper thumbnail of Effects of prior exercise or ammonium chloride ingestion on muscular strength and endurance

Med Sci Sport Exercise, 1993

Previous studies linked muscular fatigue with a decrease in blood pH. This study investigated if ... more Previous studies linked muscular fatigue with a decrease in blood pH. This study investigated if the means of altering pH affected the extent of muscular fatigue. Drug-induced and exercise-induced acidosis were compared to test the hypothesis that exercise-induced acidosis impairs subsequent muscular performance more than chemically induced acidosis. In eight male subjects acidosis was induced by ingesting 0.3 g.kg-1 ammonium chloride (AC) for one trial, by upper body exercise (UBE) for another trial, and after placebo (PL) treatment. They then completed a performance test (PT) of 50 maximal, bilateral isokinetic knee extensions. Whole blood pH before (pHpre) and after (pHpost) the PT was 7.412, 7.264, and 7.261 for PL, UBE, and AC, respectively; both AC and UBE decreased pH similarly compared with PL. Peak torque and total work during the PT were similar for PL and AC, and were significantly greater than after UBE. Six subjects performed a fourth trial after combined AC and UBE treatments causing a pHpre of 7.081, but there was no greater performance impairment than that caused by UBE alone. The results dissociate the extent of the impairment from the magnitude of the disruption in blood pH.

Research paper thumbnail of Reducing the dose of combined caffeine and ephedrine preserves the ergogenic effect

Aviation Space and Environmental Medicine, Apr 1, 2000

Background: Ingestion of a combination of 5 mg x kg(-1) caffeine (C), and 1 mg x kg(-1) ephedrine... more Background: Ingestion of a combination of 5 mg x kg(-1) caffeine (C), and 1 mg x kg(-1) ephedrine (E) was reported to have an ergogenic effect on high intensity aerobic exercise performance, but 25% of the subjects experienced vomiting and nausea while engaging in hard exercise after the treatment. The present study was undertaken to investigate whether reduced levels of C+E would alleviate the problem and maintain the ergogenic effect. Methods: Twelve healthy untrained male subjects completed four randomized and double-blind, cycle ergometer trials to exhaustion at a power output equivalent to approximately 85% Vo2peak 1.5-2 hours after ingesting a placebo (P) or a mixture of C+E in the following doses: 5 mg x kg(-1) of C plus 0.8 mg x kg(-1) of E (CLE); 4 mg x kg(-1) of C plus 1 mg x kg(-1) of E (LCE); or 4 mg x kg of C plus 0.8 mg x kg(-1) of E (LCLE). Trials were separated by 1 wk. Venous blood samples were obtained and analyzed for caffeine and ephedrine levels 1.5 h post-drug ingestion. Vo2, Vco2, VE, and RQ were measured every minute throughout the exhaustion ride. Heart rate and perceived exertion (RPE) were also recorded every 5 min and at the end of the exercise session. Results: Plasma levels of C and E immediately before the exhaustion ride were (mean +/- SD): 38.7+/-5.2 micromol x L(-1) C, 1.285+/-0.275 micromol x L(-1) E in the CLE trial; 33.2+/-5.8 micromol x L(-1) C, 1.462+/-0.283 micromol x L(-1) E in the LCE trial; 33.0+/-2.9 micromol x L(-1) C, 1.229+/-0.202 micromol x L(-1) E in the LCLE trial. The times to exhaustion for the treatment trials (CLE = 27.5+/-12.4 min, LCE = 27.6+/-10.9 min, LCLE = 28.2+/-9.3 min) were similar and were significantly greater than placebo (p = 17.0+/-3.0 min). The drugs did not affect Vo2, Vco2, or VE. Heart rates were significantly higher for the drug trials while RPE was lower compared with P. No incidents of nausea or vomiting occurred with the lowest dose of the C+E, LCLE. Conclusions: A lower dose of C+E resulted in an ergogenic effect similar in magnitude to that reported previously with a higher dose, and with a reduced incidence of negative side effects.

Research paper thumbnail of Combined caffeine and ephedrine ingestion improves run times of Canadian Forces Warrior Test

Aviation Space and Environmental Medicine, Apr 1, 1999

The ingestion of a combination of caffeine (C) and ephedrine (E) has been reported to prolong exe... more The ingestion of a combination of caffeine (C) and ephedrine (E) has been reported to prolong exercise time to exhaustion during cycle ergometry at 85% VO2max. The present study was undertaken to investigate whether this enhancement would occur in a field setting and if drug ingestion on 1 d would affect performance 1 d later. Two hours after ingesting either a combination of 375 mg of C and 75 mg E (C+E), or a placebo (P), 9 healthy male recreational runners completed six balanced and double-blind trials of the Canadian Forces Warrior Test (WT), a 3.2 km run wearing &quot;fighting order&quot; which weighed about 11 kg. The trials were performed in sets of two runs, i.e., two runs were done 24 h apart, and these sets were separated by a minimum of 7 d. The sets were: C+E trial on day 1 (D1), placebo on day 2 (P2); placebo first (P1), C+E second (D2); and placebo first (P3), placebo second (P4). In addition, 1 wk before the treatment trials the subjects performed a control trial WT. During the WT, heart rates (HR) were recorded every minute. Plasma C and E levels immediately before the WT were similar for both C+E trials, but were undetectable for all P trials. Run times (mean+/-SD) were 15.3+/-0.6, 15.4+/-0.9, 15.5+/-1.2, 15.4+/-0.9, 15.4+/-0.9, 14.8+/-0.7, and 14.6+/-0.8 min for control, P1, P2, P3, P4, D1, D2 trials, respectively. The two C+E trial run times were similar and both were significantly faster (p &lt; 0.05) than control and all placebo trials. HR during the WT was significantly higher (p &lt; 0.05) for the C+E trials compared with the other trials. WT performance was not impaired by C+E ingestion 24 h earlier. In conclusion, performance of the WT was improved by ingestion of C+E.

Research paper thumbnail of High-intensity exercise performance is not impaired by low intramuscular glycogen

Med Sci Sport Exercise, 1989

The purpose of this study was to evaluate the effects of glycogen availability on short-term, hig... more The purpose of this study was to evaluate the effects of glycogen availability on short-term, high-intensity exercise performance. Eight males completed performance evaluation tasks (PET) consisting of maximum isokinetic strength and endurance, isometric strength, and electrically evoked force of the leg extensors, twice during each of two conditions. On day 1 (D1) of the control condition (C) subjects performed the PET, followed by strenuous exercise designed to deplete glycogen stores of the leg extensors. After consuming a mixed diet for 48h (days 2 and 3) they performed the PET again on day 4 (D4). The experimental condition (E) was identical to C, except that a strictly controlled low carbohydrate diet was consumed during Days 2 and 3. Biopsies from the vastus lateralis before the PET on D4 confirmed differences between conditions in intramuscular glycogen (426 +/- 43 vs 153 +/- 60 mmol glucose units.kg-1 d.w. for C and E respectively, P less than 0.001). Results obtained from the PET were not different between conditions on D4, nor within conditions when D1 and D4 were compared. Resting blood glucose, hematological variables indicative of hydration and acid-base status, and post PET blood lactate were similar for all trials. It is concluded that short-term, high-intensity exercise performance of glycogen depleted leg extensors is not impaired.

Research paper thumbnail of Clamping end-tidal carbon dioxide during graded exercise with control of inspired oxygen

Respiratory physiology & neurobiology, Sep 25, 2016

Exercise- and hypoxia-induced hyperventilation decreases the partial pressure of end-tidal carbon... more Exercise- and hypoxia-induced hyperventilation decreases the partial pressure of end-tidal carbon dioxide (PETCO2), which in turn exerts many physiological effects. Several breathing circuits that control PETCO2 have been previously described, but their designs are not satisfactory for exercise studies where changes in inspired oxygen (FIO2) may be desired. This study is the first report of a breathing system that can maintain PETCO2 constant within a single session of graded submaximal exercise and graded hypoxia. Thirteen fit and healthy subjects completed two bouts of exercise consisting of three 3min stages on a cycle ergometer with increasing exercise intensity in normoxia (Part A; 142±14, 167±14, 192±14W) or with decreasing FIO2 at a constant exercise intensity (Part B; 21, 18, and 14%). One bout was a control (CON) where PETCO2 was not manipulated, while during the other bout the investigator clamped PETCO2 within 2mm Hg in the other (CO2Clamp) using sequential gas delivery (...

Research paper thumbnail of Exploiting Human Science Advances for Military Operations: Past Challenges & Future Vision

Research paper thumbnail of STRENGTH TRAINING MODALITIES: A computerized system for muscle strength evaluation: measurement reproducibility, validity and some normative data

National Strength Conditioning Association Journal, 1986

Research paper thumbnail of Acute altitude exposure and altered acid-base states. II. Effects on exercise performance and muscle and blood lactate

European Journal of Applied Physiology and Occupational Physiology, Feb 1, 1988

Research paper thumbnail of Blood lactate response to the Canadian Aerobic Fitness Test (CAFT)

Canadian Journal of Sport Sciences Journal Canadien Des Sciences Du Sport, Apr 1, 1992

ABSTRACT This study evaluated the blood lactate concentration ([LA-]) response to the Canadian Ae... more ABSTRACT This study evaluated the blood lactate concentration ([LA-]) response to the Canadian Aerobic Fitness Test (CAFT) in female subjects and compared the strength of prediction of VO2max determined by [LA-] and heart rate (HR). The sample was composed of 98 Canadian Forces females between the ages of 18 and 45 years. The [LA-] after each stage of the step-test was measured in all subjects by sampling blood from the fingertip. VO2max was measured directly during a maximal treadmill run in 66 of these subjects. The results showed that increasing stages of the step-test were associated with increasing [LA-]. The correlation between [LA-] after Stage 5 of the step-test and the directly determined VO2max was r = -0.72 and did not differ significantly from the correlation between HR and VO2max (r = -0.66). The relationship between [LA-] and VO2max for these females was similar to the one established earlier for males; however, the correlation between HR and VO2max for females was different from that observed in males. The present data for the females suggest that [LA-] and HR after Stage 5 of the CAFT predict VO2max equally well for females under age 40.

Research paper thumbnail of Energy Balance of Canadian Armed Forces Personnel during an Arctic-Like Field Training Exercise

Nutrients

Operating in temperature extremes frequently leads to a discrepancy in energy balance. Investigat... more Operating in temperature extremes frequently leads to a discrepancy in energy balance. Investigating the effects of operating in extreme cold temperatures on metabolic requirements has not been well described in Canadian Armed Forces (CAF) personnel. The objective was to accurately assess energy deficits using the “gold standard” methodology for measuring energy intake (EI) and energy expenditure (EE). Nutritional intake of a convenience sample of 10 CAF Class A Reservists, completing a basic military qualification (land) course under winter weather conditions, was assessed using the daily measured food intake/food waste collections. EE was measured by the doubly-labelled water method. Average EI was 2377 ± 1144 kcal/day, which was below the EE (4917 ± 693 kcal/day), despite having ~5685 kcal available in the field rations. A significant body weight loss of 2.7% was associated with the average daily energy deficit of 2539 ± 1396 kcal. As a result, participants demonstrated voluntary...

Research paper thumbnail of Comparison of dietary intakes of Canadian Armed Forces personnel consuming field rations in acute hot, cold, and temperate conditions with standardized infantry activities

Military Medical Research

Research paper thumbnail of The effects of exercise and ambient temperature on dietary intake, appetite sensation, and appetite regulating hormone concentrations

Research paper thumbnail of The Effects of Thermal Dehydration on Performance of the Wingate Anaerobic Test

International Journal of Sports Medicine

Research paper thumbnail of Energy Metabolism in Cold-Stressed Females: Implications for Predictive Modeling

Research paper thumbnail of Rate dependent influence of arterial desaturation on self-selected exercise intensity during cycling

PloS one, 2017

The purpose of this study was to clarify if Ratings of Perceived Exertion (RPE) and self-selected... more The purpose of this study was to clarify if Ratings of Perceived Exertion (RPE) and self-selected exercise intensity are sensitive not only to alterations in the absolute level of arterial saturation (SPO2) but also the rate of change in SPO2. Twelve healthy participants (31.6 ± 3.9 y, 175.5 ± 7.7 cm, 73.3 ± 10.3 kg, 51 ± 7 mL·kg-1·min-1 [Formula: see text]) exercised four times on a cycle ergometer, freely adjusting power output (PO) to maintain RPE at 5 on Borg's 10-point scale with no external feedback to indicate their exercise intensity. The fraction of inspired oxygen (FIO2) was reduced during three of those trials such that SPO2 decreased during exercise from starting values (>98%) to 70%. These trials were differentiated by the time over which the desaturation occurred: 3.9 ± 1.4 min, -8.7 ± 4.2%•min-1 (FAST), 11.0 ± 3.7 min, -2.8 ± 1.3%•min-1 (MED), and 19.5 ± 5.8 min, -1.5 ± 0.8%•min-1 (SLOW) (P < 0.001). Compared to stable PO throughout the control condition (no...

Research paper thumbnail of Modafinil Prolongs Time to Exhaustion During High Intensity Submaximal Exercise 224

Med Sci Sport Exercise, 1997

Research paper thumbnail of Blood Lactate: Its Use in the Evaluation of Exercise Performance and Training

Med Sci Sport Exercise, 1984

Research paper thumbnail of Blood Lactate: Implications for Training and Sports Performance

Sports Medicine, 1986

The blood lactate response to exercise has interested physiologists for over fifty years, but has... more The blood lactate response to exercise has interested physiologists for over fifty years, but has more recently become as routine a variable to measure in many exercise laboratories as is heart rate. This rising popularity is probably due to: the ease of sampling and improved accuracy afforded by recently developed micro-assay methods and/or automated lactate analysers; and the predictive and evaluative power associated with the lactate response to exercise. Several studies suggest that the strong relationship between exercise performance and lactate-related variables can be attributed to a reflection by lactate during exercise of not only the functional capacity of the central circulatory apparati to transport oxygen to exercising muscles, but also the peripheral capacity of the musculature to utilise this oxygen. For example, several studies contrast the relationship between VO2max and endurance running performance with that between a lactate variable and the same running performance. In every study, the lactate variable is more highly correlated with performance. Similarly, prescribing training intensity as a function of the lactate concentration elicited by the training may prove to be a means of obtaining a more homogeneous adaptation to training in a group of athletes or subjects than is obtained by setting intensity as a function of maximal heart rate or % VO2max. A review of the recent literature shows that the lactate response to supramaximal exercise is a sensitive indicator of adaptation to 'sprint training' and is correlated with supramaximal exercise performance. This review also describes the possible applications of lactate measurements to enhance the rate of recovery from high intensity exercise. Although the lactate response to exercise is reproducible under standardised conditions it can be influenced by the site of blood sampling, ambient temperature, changes in the body's acid-base balance prior to exercise, prior exercise, dietary manipulations, or pharmacological interpretation.

Research paper thumbnail of Perspectives on Retaining a DRDC Human Sciences Centre...in Toronto

Research paper thumbnail of Electro-mechanical response times and rate of force development in males and females

Medicine Amp Science in Sports Amp Exercise, Mar 1, 1986

Muscle force development is influenced by both central (pre-motor end plate) and peripheral (post... more Muscle force development is influenced by both central (pre-motor end plate) and peripheral (post-motor end plate) components. Conflicting results are available concerning gender-related differences in the central component. This study compared males and females with regard to the following electro-mechanical response variables: total reaction time, pre-motor time, electro-mechanical delay, and the rate of force development during a maximal voluntary isometric contraction (MVC) of the elbow flexors. Forty-six males and 40 females performed MVCs against a bar attached to a force transducer. Subjects were instructed to attempt to flex the elbow with maximal force as rapidly as possible after perceiving a visual stimulus. Surface electromyographic activity was recorded from the biceps brachii and was sampled simultaneously with the force transducer data at 2 kHz and stored digitally. For data analyses the subjects were separated into four groups based on the force generated during the MVC: weak females, weak males, strong females, and strong males. Neither total reaction time nor pre-motor time was significantly different across groups. The electro-mechanical delay for both male groups was significantly shorter than for both female groups. Electro-mechanical delay was weakly, but significantly, correlated with rate of force development and maximum force. During a single MVC the times required to attain 25, 50, 75, and 100% MVC were similar in all groups. The results suggest that at least part of the gender difference in maximum strength may be due to differences in electro-mechanical response times.

Research paper thumbnail of Effects of prior exercise or ammonium chloride ingestion on muscular strength and endurance

Med Sci Sport Exercise, 1993

Previous studies linked muscular fatigue with a decrease in blood pH. This study investigated if ... more Previous studies linked muscular fatigue with a decrease in blood pH. This study investigated if the means of altering pH affected the extent of muscular fatigue. Drug-induced and exercise-induced acidosis were compared to test the hypothesis that exercise-induced acidosis impairs subsequent muscular performance more than chemically induced acidosis. In eight male subjects acidosis was induced by ingesting 0.3 g.kg-1 ammonium chloride (AC) for one trial, by upper body exercise (UBE) for another trial, and after placebo (PL) treatment. They then completed a performance test (PT) of 50 maximal, bilateral isokinetic knee extensions. Whole blood pH before (pHpre) and after (pHpost) the PT was 7.412, 7.264, and 7.261 for PL, UBE, and AC, respectively; both AC and UBE decreased pH similarly compared with PL. Peak torque and total work during the PT were similar for PL and AC, and were significantly greater than after UBE. Six subjects performed a fourth trial after combined AC and UBE treatments causing a pHpre of 7.081, but there was no greater performance impairment than that caused by UBE alone. The results dissociate the extent of the impairment from the magnitude of the disruption in blood pH.

Research paper thumbnail of Reducing the dose of combined caffeine and ephedrine preserves the ergogenic effect

Aviation Space and Environmental Medicine, Apr 1, 2000

Background: Ingestion of a combination of 5 mg x kg(-1) caffeine (C), and 1 mg x kg(-1) ephedrine... more Background: Ingestion of a combination of 5 mg x kg(-1) caffeine (C), and 1 mg x kg(-1) ephedrine (E) was reported to have an ergogenic effect on high intensity aerobic exercise performance, but 25% of the subjects experienced vomiting and nausea while engaging in hard exercise after the treatment. The present study was undertaken to investigate whether reduced levels of C+E would alleviate the problem and maintain the ergogenic effect. Methods: Twelve healthy untrained male subjects completed four randomized and double-blind, cycle ergometer trials to exhaustion at a power output equivalent to approximately 85% Vo2peak 1.5-2 hours after ingesting a placebo (P) or a mixture of C+E in the following doses: 5 mg x kg(-1) of C plus 0.8 mg x kg(-1) of E (CLE); 4 mg x kg(-1) of C plus 1 mg x kg(-1) of E (LCE); or 4 mg x kg of C plus 0.8 mg x kg(-1) of E (LCLE). Trials were separated by 1 wk. Venous blood samples were obtained and analyzed for caffeine and ephedrine levels 1.5 h post-drug ingestion. Vo2, Vco2, VE, and RQ were measured every minute throughout the exhaustion ride. Heart rate and perceived exertion (RPE) were also recorded every 5 min and at the end of the exercise session. Results: Plasma levels of C and E immediately before the exhaustion ride were (mean +/- SD): 38.7+/-5.2 micromol x L(-1) C, 1.285+/-0.275 micromol x L(-1) E in the CLE trial; 33.2+/-5.8 micromol x L(-1) C, 1.462+/-0.283 micromol x L(-1) E in the LCE trial; 33.0+/-2.9 micromol x L(-1) C, 1.229+/-0.202 micromol x L(-1) E in the LCLE trial. The times to exhaustion for the treatment trials (CLE = 27.5+/-12.4 min, LCE = 27.6+/-10.9 min, LCLE = 28.2+/-9.3 min) were similar and were significantly greater than placebo (p = 17.0+/-3.0 min). The drugs did not affect Vo2, Vco2, or VE. Heart rates were significantly higher for the drug trials while RPE was lower compared with P. No incidents of nausea or vomiting occurred with the lowest dose of the C+E, LCLE. Conclusions: A lower dose of C+E resulted in an ergogenic effect similar in magnitude to that reported previously with a higher dose, and with a reduced incidence of negative side effects.

Research paper thumbnail of Combined caffeine and ephedrine ingestion improves run times of Canadian Forces Warrior Test

Aviation Space and Environmental Medicine, Apr 1, 1999

The ingestion of a combination of caffeine (C) and ephedrine (E) has been reported to prolong exe... more The ingestion of a combination of caffeine (C) and ephedrine (E) has been reported to prolong exercise time to exhaustion during cycle ergometry at 85% VO2max. The present study was undertaken to investigate whether this enhancement would occur in a field setting and if drug ingestion on 1 d would affect performance 1 d later. Two hours after ingesting either a combination of 375 mg of C and 75 mg E (C+E), or a placebo (P), 9 healthy male recreational runners completed six balanced and double-blind trials of the Canadian Forces Warrior Test (WT), a 3.2 km run wearing &quot;fighting order&quot; which weighed about 11 kg. The trials were performed in sets of two runs, i.e., two runs were done 24 h apart, and these sets were separated by a minimum of 7 d. The sets were: C+E trial on day 1 (D1), placebo on day 2 (P2); placebo first (P1), C+E second (D2); and placebo first (P3), placebo second (P4). In addition, 1 wk before the treatment trials the subjects performed a control trial WT. During the WT, heart rates (HR) were recorded every minute. Plasma C and E levels immediately before the WT were similar for both C+E trials, but were undetectable for all P trials. Run times (mean+/-SD) were 15.3+/-0.6, 15.4+/-0.9, 15.5+/-1.2, 15.4+/-0.9, 15.4+/-0.9, 14.8+/-0.7, and 14.6+/-0.8 min for control, P1, P2, P3, P4, D1, D2 trials, respectively. The two C+E trial run times were similar and both were significantly faster (p &lt; 0.05) than control and all placebo trials. HR during the WT was significantly higher (p &lt; 0.05) for the C+E trials compared with the other trials. WT performance was not impaired by C+E ingestion 24 h earlier. In conclusion, performance of the WT was improved by ingestion of C+E.

Research paper thumbnail of High-intensity exercise performance is not impaired by low intramuscular glycogen

Med Sci Sport Exercise, 1989

The purpose of this study was to evaluate the effects of glycogen availability on short-term, hig... more The purpose of this study was to evaluate the effects of glycogen availability on short-term, high-intensity exercise performance. Eight males completed performance evaluation tasks (PET) consisting of maximum isokinetic strength and endurance, isometric strength, and electrically evoked force of the leg extensors, twice during each of two conditions. On day 1 (D1) of the control condition (C) subjects performed the PET, followed by strenuous exercise designed to deplete glycogen stores of the leg extensors. After consuming a mixed diet for 48h (days 2 and 3) they performed the PET again on day 4 (D4). The experimental condition (E) was identical to C, except that a strictly controlled low carbohydrate diet was consumed during Days 2 and 3. Biopsies from the vastus lateralis before the PET on D4 confirmed differences between conditions in intramuscular glycogen (426 +/- 43 vs 153 +/- 60 mmol glucose units.kg-1 d.w. for C and E respectively, P less than 0.001). Results obtained from the PET were not different between conditions on D4, nor within conditions when D1 and D4 were compared. Resting blood glucose, hematological variables indicative of hydration and acid-base status, and post PET blood lactate were similar for all trials. It is concluded that short-term, high-intensity exercise performance of glycogen depleted leg extensors is not impaired.

Research paper thumbnail of Clamping end-tidal carbon dioxide during graded exercise with control of inspired oxygen

Respiratory physiology & neurobiology, Sep 25, 2016

Exercise- and hypoxia-induced hyperventilation decreases the partial pressure of end-tidal carbon... more Exercise- and hypoxia-induced hyperventilation decreases the partial pressure of end-tidal carbon dioxide (PETCO2), which in turn exerts many physiological effects. Several breathing circuits that control PETCO2 have been previously described, but their designs are not satisfactory for exercise studies where changes in inspired oxygen (FIO2) may be desired. This study is the first report of a breathing system that can maintain PETCO2 constant within a single session of graded submaximal exercise and graded hypoxia. Thirteen fit and healthy subjects completed two bouts of exercise consisting of three 3min stages on a cycle ergometer with increasing exercise intensity in normoxia (Part A; 142±14, 167±14, 192±14W) or with decreasing FIO2 at a constant exercise intensity (Part B; 21, 18, and 14%). One bout was a control (CON) where PETCO2 was not manipulated, while during the other bout the investigator clamped PETCO2 within 2mm Hg in the other (CO2Clamp) using sequential gas delivery (...

Research paper thumbnail of Exploiting Human Science Advances for Military Operations: Past Challenges & Future Vision

Research paper thumbnail of STRENGTH TRAINING MODALITIES: A computerized system for muscle strength evaluation: measurement reproducibility, validity and some normative data

National Strength Conditioning Association Journal, 1986

Research paper thumbnail of Acute altitude exposure and altered acid-base states. II. Effects on exercise performance and muscle and blood lactate

European Journal of Applied Physiology and Occupational Physiology, Feb 1, 1988

Research paper thumbnail of Blood lactate response to the Canadian Aerobic Fitness Test (CAFT)

Canadian Journal of Sport Sciences Journal Canadien Des Sciences Du Sport, Apr 1, 1992

ABSTRACT This study evaluated the blood lactate concentration ([LA-]) response to the Canadian Ae... more ABSTRACT This study evaluated the blood lactate concentration ([LA-]) response to the Canadian Aerobic Fitness Test (CAFT) in female subjects and compared the strength of prediction of VO2max determined by [LA-] and heart rate (HR). The sample was composed of 98 Canadian Forces females between the ages of 18 and 45 years. The [LA-] after each stage of the step-test was measured in all subjects by sampling blood from the fingertip. VO2max was measured directly during a maximal treadmill run in 66 of these subjects. The results showed that increasing stages of the step-test were associated with increasing [LA-]. The correlation between [LA-] after Stage 5 of the step-test and the directly determined VO2max was r = -0.72 and did not differ significantly from the correlation between HR and VO2max (r = -0.66). The relationship between [LA-] and VO2max for these females was similar to the one established earlier for males; however, the correlation between HR and VO2max for females was different from that observed in males. The present data for the females suggest that [LA-] and HR after Stage 5 of the CAFT predict VO2max equally well for females under age 40.