Stanley P. Brown

Pathological versus physiological left ventricular hypertrophy: a review.

Left ventricular hypertrophy is recognized as an independent risk factor for cardiovascular morbid events. The primary mechanisms responsible for stimulating it are unknown. Epidemiological theories suggest that left ventricular hypertrophy is a continuous variable with no threshold, while morphological studies argue that it is the structure, or quality, and function of the myocardium (and therefore non-continuous), not the quantity of the myocardial mass, that poses the cardiovascular risk. Although left ventricular hypertrophy has been classically viewed as an adaptive response of the cardiovascular system to an imposed load, it has been demonstrated that haemodynamic overloading in selected hypertensive patients is not the sole determinant of left ventricular structure and function. Pathological and physiological states of left ventricular hypertrophy have been described primarily using criteria focusing on normal chamber performance and oxygen delivery as well as the reversibility of the hypertrophy once the overload is removed. Both states are also defined by the nature of the imposed load and the resulting myocardial adaptations. This review addresses the pathological and physiological states of left ventricular hypertrophy, the hypertrophy patterns, and the corresponding structural and functional characteristics, together with some of the biochemical factors thought to influence remodelling.

PERCEPTUAL RESPONSES TO DEEP WATER RUNNING AND TREADMILL EXERCISE

Perceived exertion during deep water running and treadmill exercise was measured to examine gender and mode-specific responses. Deep water running to VO2 peak was performed in 3-min. stages at leg speeds controlled by a metronome. Treadmill exercise was performed at matched leg speeds. VO2 and heart rate were continuously monitored by open circuit spirometry and radiotelemetry. Perceived exertion was measured using Borgs 6–20 point scale. Statistical analyses were performed using multiple linear regression with dummy coded discrete variables. Ratings of perceived exertion were significantly higher during deep water running when exercising at equal leg speeds. Mean rated perceived exertion at each stage of the test for either exercise mode was not significantly different between men and women.

Standardization indices of cardiac hypertrophy in weight lifters

In order to investigate further the use of standardization procedures to determine training effects on cardiac dimension and function, two groups of subjects were analysed noninvasively. A control group of sedentary men (n = 7) and an experimental group of weight lifters (n = 12) volunteered for a standard M-mode echocardiographic assessment. Indices of cardiac function as well as absolute left ventricular dimensions and left ventricular mass were similar between the groups. Standardizing for body surface area and body weight separated the groups. The weight lifters were shown to have a more muscular left ventricular posterior wall. The weight lifters also demonstrated a dilated left ventricle when indexing for body surface area. All other dimensional and volumetric indices were non-significant. The present investigation underlines the need for matching control and experimental groups to biometric variables in order to avoid misinterpreting cardiac enlargement. There is evidence for a true relative hypertrophy in weight lifters as indicated by similar absolute cardiac dimensions and similar biometric variables. Therefore, when evaluating athletes engaged in a chronic pressure overload, cardiac hypertrophy indices should consider body surface area (BSA), body weight and lean body weight (LBW). Future work in this field should incorporate rigorous controls on all biometric variables for better interpretation of hypertrophy in relative or absolute terms.

Effects of Carbohydrate Supplementation on Force Output and Time to Exhaustion During Static Leg Contractions Superimposed with Electromyostimulation

Abstract Wax, B, Brown, SP, Webb, HE, and Kavazis, AN. Effects of carbohydrate supplementation on force output and time to exhaustion during static leg contractions superimposed with electromyostimulation. J Strength Cond Res 26(6): 1717–1723, 2012—The purpose of this study was to investigate the effects of carbohydrate ingestion on force output and time to exhaustion using single leg static contractions superimposed with brief periods of electromyostimulation. Six trained male subjects participated in a randomized, counterbalanced, double-blind study. The subjects were randomly assigned to placebo (PL) or carbohydrate (CHO). The subjects in CHO consumed 1 g of carbohydrate per kilogram of body mass loading dose and 0.17 g of carbohydrate per kilogram of body mass every 6 minutes during the exercise protocol. The PL received an equal volume of a solution made of saccharin and aspartame. The exercise protocol consisted of repeated 20-second static contractions of quadriceps muscle at 50% maximal voluntary contraction followed by 40-second rest until failure occurred. Importantly, the force output during quadriceps maximal voluntary contraction strength with superimposed electromyostimulation was measured in the beginning and every 5 minutes during the last 3 seconds of static contractions throughout the exercise protocol. Venous blood samples were taken preexercise, immediately postexercise, and at 5 minutes postexercise and analyzed for blood lactate. Our results indicate that time to exhaustion (PL = 16.0 ± 8.1 minutes; CHO = 29.0 ± 13.1 minutes) and force output (PL = 3,638.7 ± 524.5 N; CHO = 5,540.1 ± 726.1 N) were significantly higher (p < 0.05) in CHO compared with that in PL. Data suggest that carbohydrate ingestion before and during static muscle contractions can increase force output and increase time to exhaustion. Therefore, our data suggest that carbohydrate supplementation before and during resistance exercise might help increase the training volume of athletes.

Physiological correlates with perceived exertion during deep water running.

The purpose of this study was to investigate the relationship between perceived exertion and physiological variables during deep water running. Deep water running to VO2 peak was performed in 3-min. stages at leg speeds controlled by a metronome. VO2 and heart rate were continuously monitored by open circuit spirometry and radiotelemetry. Perceived exertion was measured using Borgs 6- to 20-point scale. Multiple regression analysis with a forward solution was used to establish the relations of the measures of perceived exertion with the measures of oxygen uptake, carbon dioxide production, pulmonary ventilation, respiratory exchange ratio, and respiratory rate. %VO2 max was the most important variable predicting perceived exertion. Men and women (ns = 12) reported using different sensory cues to perceive exertion during deep water running.

The Prediction of Oxygen Consumption in Cardiac Rehabilitation Patients During Arm Ergometry

Background The purpose of this investigation was to develop a regression equation to predict oxygen consumption VO2 during arm ergometry in cardiac rehabilitation patients. A second purpose was to determine the accuracy of two currently used prediction equations. Methods Twenty-three male and eight female patients with cardiac disease participated in this study. Age was 36 to 83 (x ± standard deviation = 62.6 ± 11.2) years, weight was 44.7 to 129.8 (83.0 ± 17.4) kg, and height was 154.3 to 185.4 (171.7 ± 9.1) cm. Subjects performed submaximal arm ergometry during 3-minute stages in 24.5 watt increments with a 2-minute rest period separating each stage. A correlated t-test was used to measure the mean difference between the prediction equations VO2 and the actual VO2. Results The results show that both equations could not provide accurate estimates of VO2 for cardiac patients. Multiple linear regression revealed that body mass, watts(W), age, and watts squared (W2) were significant predictors of VO2 during arm ergometry. The regression equation: VO2(mL/min) = 253.381 - 2.001 (age) + 2.947 (body mass) + 9.764(W) + 0.026 (W2) has a R of 0.96 (P Conclusions These results indicate that the use of the equation generated in this study will provide accurate estimates of VO2 for cardiac rehabilitation patients. In addition, one prediction equations significantly (P = 0.0001) overestimates by an average of 21% across all workloads and the other overestimates the first stage by 13% and underestimates Stages III and IV by an average of 12%.

Effects of supplemental carbohydrate ingestion during superimposed electromyostimulation exercise in elite weightlifters.

Abstract Wax, B, Kavazis, AN, and Brown, SP. Effects of supplemental carbohydrate ingestion during superimposed electromyostimulation exercise in elite weightlifters. J Strength Cond Res 27(11): 3084–3090, 2013—The purpose of this investigation was to test the effects of carbohydrate supplementation on blood parameters and force output during superimposed electromyostimulation (SEMS) single-leg isometric contractions. We hypothesized that carbohydrate ingestion before and during muscle contractions would lead to greater glucose availability and greater total force output for the session. Six elite resistance trained male subjects participated in a randomized, counterbalanced, double-blind study. The subjects were randomly assigned to placebo (PL) or carbohydrate (CHO). The subjects in CHO consumed 1 g of carbohydrate per kilogram of body mass loading dose and 0.17 g of carbohydrate·per kilogram of body mass every 6 minutes during the exercise protocol. The PL received an equal volume of a solution made of saccharin and aspartame. The exercise protocol consisted of repeated 20-second isometric contractions of quadriceps muscle at 50% maximal voluntary contraction followed by 40 seconds of rest until failure occurred. Importantly, quadriceps maximal voluntary contraction with SEMS was performed in the beginning and then every 5 minutes during the last 3 seconds of isometric contractions throughout the exercise protocol. Venous blood samples were taken preexercise, immediately postexercise, and at 5 minutes postexercise and analyzed for glucose, nonesterified fatty acids, and glycerol. Our results indicate that CHO ingestion increased (p < 0.05) plasma glucose, but no significant differences (p > 0.05) were detected for nonesterified fatty acids or glycerol. Importantly, total force output during exercise protocol was higher (p < 0.05) in CHO compared with that in PL. Therefore, our data suggest that CHO supplementation before and during exercise may be beneficial for individuals performing high-volume resistance training.

The effects of acute exercise on levels of erythrocyte 2,3‐bisphosphoglycerate: A brief review

The effects of acute and chronic exercise on factors related to oxygen transport have been studied extensively. This process has led investigators to quantify the relationship between variables such as exercise mode and intensity, and red cell 2,3-bisphosphoglycerate (2,3-BPG) concentration. Anaerobic forms of exercise associated with a large blood lactate appearance and greatly elevated catecholamines initially decrease 2,3-BPG after exercise due to inhibited glycolysis, but there appears to be a delayed increase if sampling is continued into recovery. Aerobic forms of exercise have shown both increases and decreases. Therefore, whether 2,3-BPG is increased or decreased during and after exercise appears to be related to the exercise and blood sampling protocols employed. Further research involving resistance exercise protocols eliciting very high blood lactate and catecholamine concentrations may be beneficial in establishing a relationship between sympathetic stress response and the serial sampling of 2,3-BPG in the post-exercise recovery period. Also, in vitro analysis of the effects of the catecholamines, oxygen tension, lactate and adenosine may be helpful in understanding the dose-response relationship between these variables and 2,3-BPG concentration.

Prediction of the oxygen cost of the deadlift exercise

The purpose of this study was to examine the relationship between total estimated work, bar load and total oxygen consumption (TVO2) during the deadlift exercise. Forty-two observations of TVO2 during a wide range of deadlifting bouts were made on a heterogeneous sample of 10 males and 14 females. TVO2 was measured by standard open-circuit spirometry. An R of 0.912 for work and TVO2 indicated that total estimated work during deadlifting can be used to predict oxygen cost accurately. The calculated regression equation was TVO2 (litres of O2) = 2.63 + 0.80 work (kJ) with a S.E.E. of 1.50 litres O2. An R of 0.909 for bar load and TVO2 indicated essentially the same predictability using bar load as the independent variable. The calculated regression equation was TVO2 (litres O2) = 2.88 + 0.005 bar load (kg) with a S.E.E. of 1.5 litres O2. Care should be taken when converting oxygen cost to energy expenditure values using non-protein R equivalents, since underestimations are likely, due to the heavy glycolytic involvement.

Regression of oxygen consumption on heart rate during supported and unsupported deep water running in healthy mixed gender subjects

The purpose of this study was to investigate the relationship between heart rate and oxygen consumption (VO2) during the performance of unsupported and supported deep water running (DWR) in young healthy males and females. A second purpose was to compare regression of predicted VO2 on heart rate between the two methods of support (i.e., unsupported vs vest supported). Thirty‐three college‐aged students (18 males and 15 females), aged 19 to 28 years, volunteered for this study. Each subject completed practice sessions until satisfactory DWR performance was attained. Subjects returned for a VO2peak test in the water on a subsequent day. The test involved the performance of a DWR graded exercise test at a metronome cadence of 72 strides‐min−1 with a cadence increase of 12 strides min”1 in each subsequent 3 minute stage. Heart rate and VO2 were monitored continuously throughout the test. Statistical analysis of the difference in physiological stimulus between supported and unsupported DWR in female and male s...