Call number: LD2668 .T4 1984 H365 / Master of Science

Call number: LD2668 .T4 1984 R516 / Master of Science

Call number: LD2668 .T4 1985 A32 / Master of Science

Call number: LD2668 .T4 1986 E23 / Master of Science / Kinesiology

An attempt was made to evaluate the applicability of a theorized model concerning plasma lactic acid kinetics to running performance assessment. This model incorporated two distinct lactate thresholds identified as the aerobic threshold (AerT) and the anaerobic threshold (AT). Two groups of males with different levels of fitness were tested. Group 1 (n = 5) consisted of recreational athletes (͞X VO₂ max = 49.3 ml/kg•min⁻¹) who ran less than 20 miles per week, while Group 2 (n = 6) were highly trained runners (͞X VO₂ max = 65.5 ml/kg•min⁻¹) who all ran at least 40 miles per week. All subjects participated in two incremental work load (IWL) and four constant work load (CWL) tests that consisted of horizontal treadmill running at different speeds. The IWL tests elicited linear increases in VO₂ and were highly correlated for both Group 1 (r = .986) and Group 2 (r = .999). However, three unbiased observers found the identification of both AerT and AT, using independent lactate and respiratory gas exchange "breakpoints," very subjective in nature. The test-retest reliablity was generally poor and varied considerably among both the observers and the individual predictor variables. The validity of the respiratory gas exchange predictors was then evaluated against the criterion lactate thresholds using the estimates of a fourth, more experienced observer. The resultant correlation coefficients were generally not high, while t-test evaluation demonstrated significant (p < .05) differences in fifty percent of the cases. This same observer then pooled all of the ventilatory predictors in an effort to better estimate both AerT and AT indirectly. These indirect ventilatory estimates consistently underpredicted the criterion lactate thresholds. This finding suggests that increases in running speeds may confound the normal associate between plasma lactate and ventilation at increasing work levels. Arbitrary lactate concentrations of 2mmol/2 and 4 mmol/L were further evaluated as threshold predictors. This methodology consistently overpredicted the criterion lactate thresholds in terms of VO₂. When any of these AerT and AT threshold estimates were compared to the lactate responses during the appropriate CWL test, no meaningful relationship were found. These observations question the physiological significance of both AerT and AT evaluation during treadmill running, as well as pointing out the difficulty in reliably detecting both plasma lactate thresholds regardless of the methodology.

Four Greyhound dogs and six horses were utilized to study the physiological mechanisms associated with the development of an exercise training-induced hypervolemia. The animals were used in two separate experiments and were trained for 14 days on a treadmill ergometer and the data were used to formulate conclusions regarding the physiological and practical implications related to the phenomenon. The data reported in this dissertation indicated that exercise training will cause an expansion of the plasma volume in the Greyhound dog (+27%, P < 0.05) and the horse (+29.1% P < 0.05). Physiologically the result is similar in man, the dog, and the horse, however, the mechanisms by which this adaptation is reached appears to differ in each of the species. In the dog, water intake (+33%, P < 0.05) appears to be the primary mechanism for the increase in fluid volume. In the horse, renal control mechanisms (24-hr urine output -24.5%, P < 0.05) appear to be the primary mechanism with those that control the retention of solutes other than sodium predominating over those that control the reabsorption of sodium and water. Based upon the literature, it appears that in man, renal mechanisms predominate the hypervolemic response and mechanisms which control the conservation of sodium appear to be most active in the defense of the tonicity and volume of the vascular compartment. These species differences are important to the understanding of the physiology behind the onset of the training-induced hypervolemia and they provide pertinent information upon which decisions regarding the choice of animal models for future research.

No description available.

This study was conducted to determine if either calcium intake or physical activity is related to bone mineral status in children and youth aged 10 to 15 years. Subjects (n = 30) with high, medium, and low bone mineral status were selected based on radius bone mineral index measurements from a sample of 108 subjects measured 9 to 12 months previously. Calcium intake was estimated from two 24-hour recalls and a food frequency questionnaire. Assessment of activity level was conducted by questionnaire. Single photon absorptiometry was used to obtain bone mineral content (g/cm) and bone mineral index (g/cm²) measurements for the radius and ulna at the midshaft and distal sites. Calcium intake and activity level were found to be similar among the bone mineral index groups. Using regression analysis, however, calcium intake was shown to be significantly related to midshaft ulna bone mineral index and activity level (sports participation) was found to be significantly related to distal ulna bone mineral index.

The importance of muscle glycogen as a fuel source during exercise has been well documented. Maintaining a high glycogen level before and during activity is a major determinant of performance. Elevation of glycogen levels during recovery from both aerobic and anaerobic bouts of exercise is critical. The purpose of this investigation was to determine the effect of a solid carbohydrate feeding on glycogen resynthesis following aerobic and anaerobic exercise. Eight male cyclists were recruited for this investigation. One hour ride trial, 70 % VO2max followed with feeding (HRY), one sprint trial followed with feeding (SPY), and one sprint trial followed with no feeding (SPN) were randomly performed and separated by ten days. Feeding trials consisted of a solid CHO source (1g CHO per kg bw per hr) fed for four hours of recovery following one hour of passive recovery with no food. Muscle biopsies were obtained immediate post and at six hours of recovery. Bloods were collected at 1, 4, and 30 minutes of recovery for lactate determination. Muscle specimens were analyzed for glycogen and lactate. Muscle glycogen (mmol • kg protein') levels post exercise for HRY, SPN, and SPY trial were 336.9±48.1, 481.0±47.0, and 417.5±26.4, respectively with HRY significantly lower than SPN. The increase in muscle glycogen six hours post-exercise for HRY, SPN, and SPY trials were 117.9±24.8, 29.5 ±22.2, and 207.2 ±20.4, respectively, which were all significantly different (P < 0.05). Blood lactate at + 1 minute for HRY, SPN, and SPY trials were 3.4±.5, 20.6±1.2, and 19.9±1.3 mM, respectively. These data suggest that an athlete training twice during the day with both anaerobic and aerobic components will have greater muscle glycogen available later in the day if anaerobic training is completed first in the day, providing adequate carbohydrate is consumed between bouts. / School of Physical Education

Several studies have reported that rating of perceived exertion (RPE) covaries more with blood lactate concentration (BLC) than other measures of relative exercise intensity. If BLC is used as the intensity criterion, then RPE could be used as a valid tool for exercise prescription. However, few have shown the relationship between RPE and BLC across a variety of graded exercise tests (GXTs) and exercise training settings. The purpose of this study was to determine if differences exist in RPEs at matched BLC between two GXTs and steady state exercise in the field setting. Thirteen healthy males (25 ± 5.3 yrs) completed two maximal treadmill protocols (Bruce and Balke) and one steady state exercise trial on a treadmill at two intensities which lasted approximately 7 minutes each. The intensities (40% & 70% max heart rate reserve) were below and above their ventilatory threshold. RPEs were recorded during the last minute of each workload of the field trial (FT). Immediately following the end of each workload, blood samples were collected for BLC analysis. RPEs from the FT were compared with RPEs from the GXTs at matched BI-Cs using a repeated measures ANOVA across exercise trials. The results show that there were no significant differences in RPEs at a matched BLC of 1.5 mM between the FTand and the Bruce and Balke GXT at the lower intensity, with the RPEs being 9.6 ± 1.7, 9.8 ± 2.6, and 10.2 ± 2.4, respectively. However, at the higher intensity, RPEs at a matched BLC of 3.0 mM were significantly different, with the FT < Bruce < Balke (11.9 ± 1.9, 13.5 ± 2.2 and 15.2 ± 2.0, p < 0.05). These results suggest that the relationship between RPE and BLC established during a GXT may not be transferable to the exercise training setting at exercise intensities in the typical prescription range of 50-85%. Therefore, using RPE for exercise prescription may not be an effective method for regulating exercise intensity according to BLC. / School of Physical Education