J. B. Mitchell

Effects of repeated days of intensified training on muscle glycogen and swimming performance.

Twelve, highly trained male swimmers were studied before, during, and after 10 successive days of increased training in an attempt to determine the physical effects of training over-load. Their average training distance was increased from 4,266 to 8,970 m.d-1, while swimming intensity was maintained at 94% (SE +/- 2%) of their maximal oxygen uptake, resulting in an average caloric cost during training of 2,293 kcal.d-1 (+/- 74). As a result of the intensified training regimen, the swimmers experienced local muscular fatigue and difficulty in completing the training sessions. Nevertheless, their swimming power, sprinting (s.22.86 m-1), endurance (s.365.8 m-1) performance, aerobic capacity, and muscle (m. deltoid) citrate synthase were unchanged as a consequence of the 10-d training regimen. Four of the 12 swimmers were, however, unable to tolerate the heavier training demands, and were forced to swim at significantly slower (P less than 0.05) speeds during the training sessions. These men were found to have significantly reduced muscle glycogen values, which was the result of their abnormally low carbohydrate intake. The findings of this research suggest that some swimmers may experience chronic muscular fatigue as a result of their failure to ingest sufficient carbohydrate to match the energy demands of heavy training.

Physiological responses to successive days of intense training in competitive swimmers

To examine the physiological responses to successive days of intense training, 12 male collegiate swimmers doubled their training distance (4,266 +/- 264 to 8,970 +/- 161 m.d-1) while maintaining the intensity at approximately 95% VO2max for 10 d. Blood samples were obtained pre-exercise and immediately and 5 min after a sub-maximal (approximately 95% VO2max) front crawl swim (365.8 m) on days 0, 5, and 11. Swim performance was assessed from a maximal front crawl swim (365.8 m), two maximal front crawl sprints (22.9 m), and a semi-tethered swim power test. No significant changes were observed in performance. Pre-exercise serum cortisol (17.5 +/- 1.5, 19.5 +/- 1.6, and 20.6 +/- 1.2 micrograms.dl-1 for days 0, 5, and 11, respectively) and creatine kinase (56.2 +/- 7.7, 93.1 +/- 10.1, and 119.0 +/- 23.1 U.l-1 for days 0, 5, and 11, respectively) values were significantly elevated (P less than 0.05) on days 5 and 11 compared to day 0. Resting plasma catecholamine concentrations were higher but not significantly different (P greater than 0.05) at the end of the training period. Measurements of hemoglobin and hematocrit indicated a relative increase of 11.4 +/- 2.7% (P less than 0.05) in estimated plasma volume during the training period. Resting blood glucose values were unaffected by the training regimen while small but significant decreases in resting blood lactate values (1.01 +/- 0.06, 0.85 +/- 0.06, and 0.86 +/- 0.06 mmol.l-1 for days 0, 5, and 11, respectively) were observed on days 5 and 11. Resting heart rate and systolic blood pressure were not affected by the increased training load.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of sodium bicarbonate on sprint performance: Relationship to dosage

The purpose of this investigation was to determine the minimum oral dosage of bicarbonate needed to significantly elevate blood bicarbonate and the influence of induced alkalosis on performance in high-intensity, short-duration exercise. Nine endurance-trained cyclists performed four 2-min sprints on separate occasions using an isokinetic cycle ergometer (Fitron, Cybex, Inc.). One hour before each test, the cyclists consumed either a placebo (A), a solution of 0.10 g NaHCO3.kg-1 body weight (B), a solution of 0.15 g NaHCO3.kg-1 body weight (C), or a solution of 0.20 g NaHCO3.kg-1 body weight (D) in random order. Arterialized venous blood was taken before (PRE) and after (POST) ingestion, and 1, 3, 5, 10, and 15 min following the 2-min bike sprint. The results showed a significant increase in POST blood bicarbonate, and the elevation was incrementally related to the dosage. There was, however, no significant improvement in performance. Total work (mean +/- SE) for each treatment (N.m per 2 min) were: A, 47,267 (+/- 2,472); B, 47,004 (+/- 3,094); C, 46,312 (+/- 2,964); and D, 47,190 (+/- 2,621). The results of this study show that incremental doses of NaHCO3 of 0.20 g.kg-1 and below produce incremental elevations in blood bicarbonate but do not produce improvements in performance for a sprint bout lasting 2 min.

Exercise-induced muscle damage: effect on circulating leukocyte and lymphocyte subsets.

The purpose of this study was to determine the effect of downhill and level running on circulating leukocyte and lymphocyte subsets and T lymphocyte activation. Using a random cross-over design, 10 runners completed two trials of 60 min of level running (0% grade; LR) and downhill running (-10% grade; DHR) at 70% of level VO2max. Blood samples were obtained preexercise and immediately postexercise (POST) and at 1.5, 12, 24, and 48 h of recovery. Creatine kinase activity peaked at 12 h of recovery from DHR and was not significantly altered following LR. The number of total T, CD16+, CD3+CD56+ cells were significantly higher POST DHR compared with LR. Leukocyte and neutrophil counts were significantly higher at 1.5 and 12 h of recovery from DHR compared with LR. The number of activated CD8+ cells (CD25+ CD8+) was significantly higher at 12 h of DHR compared to LR. Total T cells were significantly reduced at various time points during the 48 h of recovery from LR and DHR. In summary, DHR relative to LR resulted in a greater mobilization of lymphocytes (post), neutrophils (1.5-12 h of recovery) and activation of CD8+ cells at 12 h of recovery. In addition, reductions in circulating T lymphocyte subsets occurred following both conditions.

The influence of exercise intensity on heat acclimation in trained subjects.

Low-intensity exercise (less than or equal to 50% VO2max) has been demonstrated to produce heat acclimation (HA) in trained subjects. The purpose of this study was to determine whether shorter-duration, moderate-intensity exercise would also result in HA. Nine trained runners performed two 9-d exercise heat-stress protocols. Each protocol consisted of a 90-min heat tolerance test on days 1 (HTT1) and 9 (HTT2). On days 2-8 the subjects exercised at 50% VO2max for 60 min.d-1 (T50) or at 75% VO2max for 30-35 min.d-1 (T75). Final HTT2 heart rate and rectal temperature (Tr) were significantly (P less than 0.001) reduced, as compared to HTT1, with no differences between T50 and T75. Both protocols resulted in significant (P less than 0.05) reductions in HTT2 pre-exercise Tr and total exercising caloric expenditure, both of which are known to contribute to HA. No changes in resting plasma volume, osmolality, protein, post-HTT aldosterone, and exercising sweat rate were observed. These results demonstrate that equal levels of HA were obtained with T50 and T75, which suggests that moderate-intensity, short-duration exercise in the heat can produce HA in trained subjects.

Gastric emptying: influence of prolonged exercise and carbohydrate concentration.

Gastric emptying: influence of prolonged exercise and carbohydrate concentration, Med. Sci. Sports Exerc., Vol. 21, No. 3, pp. 269-274, 1989. The purpose of this study was to examine the effects of serial feedings of different concentrations of carbohydrate (CHO) on gastric emptying and to compare the rates of gastric emptying at rest and during prolonged exercise. Solutions of 0, 6, 12, and 18 g. 100 ml-1 (WP, CHO-6, CHO-12, and CHO-18, respectively) were tested. Ten trained male cyclists performed five trials involving 120 min of cycling. The first 105 min were at 70% of VO2max, and the final 15 min were an all-out self-paced performance ride. In one of the five trials, the subjects rode intermittently, completing seven 15-min rides at 70% of VO2max, with 3 min of rest between each ride. Every 15 min, approximately 150 ml (8.5 ml.kg-1.h-1) of one of the four test solutions were consumed. (In the intermittent trial, the CHO-12 solution was used.) Subjects were also tested during 120 min of seated rest using the above feeding schedule (6% solution). Gastric residue was determined by stomach aspiration following the performance ride. The volumes emptied during the CHO-12 and CHO-18 trials (1,049.8 and 889.2 ml) were significantly different from each other and were less than during the WP and CHO-6 trials (1,210.3 and 1,185.6 ml) (P less than 0.05). CHO delivery was significantly higher in the CHO-12 and CHO-18 trials (126 and 160 g) compared to the CHO-6 trial (71.1 g).(ABSTRACT TRUNCATED AT 250 WORDS)

The role of anaerobic ability in middle distance running performance

SummaryThe purpose of this study was to assess the relationship between anaerobic ability and middle distance running performance. Ten runners of similar performance capacities (5 km times: 16.72, SE 0.2 min) were examined during 4 weeks of controlled training. The runners performed a battery of tests each week [maximum oxygen consumption (VO2max), vertical jump, and Margaria power run] and raced 5 km three times (weeks 1, 2, 4) on an indoor 200-m track (all subjects competing). Regression analysis revealed that the combination of time to exhaustion (TTE) during theVO2max test (r2=0.63) and measures from the Margaria power test (W·kg−1,r2=0.18 ; W,r2=0.05) accounted for 86% of the total variance in race times (P<0.05). Regression analysis demonstrated that TTE was influenced by both anaerobic ability [vertical jump, power (W·kg−1) and aerobic capacity (VO2max, ml·kg−1·min−1)]. These results indicate that the anaerobic systems influence middle distance performance in runners of similar abilities.

ADAPTATION TO ECCENTRIC EXERCISE: EFFECT ON CD64 AND CD11b/CD18 EXPRESSION: 988

The primary purpose of the study was to examine circulating neutrophils and monocytes and their plasma membrane expression of CD64, CD11b, and CD18 after two bouts (B1 and B2) of eccentric exercise. Subjects (n = 10) performed 25 forced-lengthened contractions of the forearm flexors on two occasions separated by 3 wk. Blood samples were obtained before exercise and at 1.5, 6, 12, 24, 48, 72, and 96 h of recovery. CD64, CD11b, and CD18 expression was determined via direct immunofluorescence and used as an indicator of neutrophil and monocyte activation. Creatine kinase activity (B1 = 1,390, B2 = 108 U/l), myoglobin (B1 = 163, B2 = 41, ng/dl), and muscle soreness and tenderness were higher (P < 0.01) after B1 compared with B2. Neutrophils at 6, 12, and 96 h were higher (P < 0.05) for B1 vs. B2. CD11b expression on neutrophils was 2.7-fold higher at 72 h for B1 vs. B2. CD64 expression on neutrophils at 72 and 96 h was 1.4- and 1.9-fold higher, respectively, for B1 vs. B2. At 72 and 96 h, CD18 and CD64 expression on monocytes was 1.3-fold higher for B1 vs. B2. The observed changes were not significantly correlated with changes in creatine kinase activity or myoglobin. In conclusion, the adaptation to eccentric arm exercise was associated with a reduction in circulating neutrophils and a lower state of neutrophil and monocyte activation.

MAXIMAL ACCUMULATED OXYGEN DEFICIT OF RESISTANCE TRAINED MEN 404

The primary purpose of the study was to compare maximal accumulated oxygen deficit (MAOD) in resistance-trained (RT), endurance-trained (ET), and untrained men (UT). A secondary purpose was to determine the influence of leg muscle mass (MM) on MAOD by examining the relationship between MM and MAOD and by comparing MAOD expressed relative to MM between the groups. MAOD was determined during 2-4 min of constant-load fatiguing cycling. MM, estimated via anthropometric measurements, was higher (p < .05) for RT (mean +/- SE; 25.5 +/- 3.4 kg) compared to ET (20.3 +/- 3.5) and UT (21.6 +/- 3.4). MAOD in liters O2eq was larger in RT (4.75 +/- 0.3) compared to UT (3.07 +/- 0.3) and ET (3.75 +/- 0.3). A significant positive correlation was observed between MAOD (LO2eq) and MM (kg) for RT only (RT, r = .85; ET, r = .55; UT, r = .20). Based on the correlational and mean MM data, the higher MAOD (LO2eq) in RT relative to ET and UT is predominantly the result of their larger leg muscle mass.