Previous studies have shown that sodium bicarbonate ingestion prior to exercise may improve performance during repeated (interval) bouts. To examine the practical implications of such findings, seven collegiate swimmers participated in simulated swim competitions of multiple events following sodium bicarbonate (B) ingestion, placebo (P) ingestion and control (C--no ingestion) treatments. Each swimmer reported to the laboratory 1 h prior to the simulated competitions (72 h apart) and was randomly assigned to one of the three experimental treatments. Competition consisted of one relay (100 yards; 91.4 m) and two individual (200 yards; 182.8 m) swimming events with 20 min rest between events. Analysis of variance (ANOVA) with repeated measures revealed no significant differences in performance times as a result of the three treatments (P greater than 0.05). The results suggest that sodium bicarbonate ingestion prior to swim competition consisting of significant rest intervals between events is not an ergogenic procedure.
Considerable research has shown significant increases in beta-endorphin levels after aerobic activity. These increases and their accompanying euphoric effect have been suggested as a possible psychophysiological mechanism underlying the exercise-dependence syndrome. The relationship between plasma beta-endorphin levels and a tendency towards exercise dependence, however, has not been established. To examine this relationship, 8 women trained in aerobic dance completed an exercise-dependence assessment prior to participation in a 45-min. session of continuous aerobic dance. Plasma beta-endorphin concentration was measured both prior to and following the aerobics routine. A Student t test for paired observations indicated that mean plasma beta-endorphin levels (+/- SE) were significantly higher after the aerobics routine (11.96 +/- 1.3 pg beta-EP.ml-1) than preexercise levels (8.62 +/- 1.4). However, beta-endorphin difference values (% change) were not significantly correlated with scores on the exercise-dependence survey. Those data suggest that scores on exercise dependence are not related to changes in plasma beta-endorphin levels after aerobic exercise.
Previous research investigating the response of plasma beta-endorphins (beta-EP) to resistance exercise has resulted in equivocal findings. To further examine the effects of resistance exercise on beta-endorphin immunoreactivity, six resistance-trained athletes participated in a three-set series of eight repetitions of isotonic exercise. All exercises were performed at 80% maximal effort. Blood was sampled from the group by venepuncture, both prior to and following the exercise bout, and beta-endorphin concentration was determined by radioimmunoassay. The results indicated that mean (+/- S.E.) plasma levels of beta-endorphins following exercise (18.04 +/- 3.4 pg beta-EP ml-1) were not significantly changed from pre-exercise (control) levels (19.59 +/- 2.4 pg beta-EP ml-1), although there was considerable inter-individual variability. Our results support previous research which has reported no significant changes in beta-endorphin immunoreactivity following resistance exercise, as well as reported findings of considerable variability in the beta-endorphin response to exercise.
Previous research investigating the response of plasma P-endorphins to resistance exercise has resulted in equivocal findings. To examine further the effects of resistance exercise on 3-EP immunoreactivity, 10 male and 10 female college-age students participated in a series of controlled isotonic resistance exercises. The session consisted of three sets of eight repetitions at 80% of one repetition maximum (1-RM) for each of the following exercises: (1) bench press; (2) lateral pull-downs; (3) seated arm curls; and (4) military press. Blood plasma was sampled both before and after the lifting routine and P-endorphin levels were determined by radioimmunoassay. A Students t test for paired samples indicated that mean(s.e.) plasma P-endorphin levels after exercise (10.5(1.3) pg R-EP ml-') were significantly decreased as compared with pre-exercise (control) levels (16.5(1.2), P < 0.05). While the mechanism(s) contributing to the decrease in immunoreactivity is unclear, it may be the result of the synergistic effect of R-EP clearance during rest intervals and changes in psychological states between sampling.Keywords: Resistance exercise, P-endorphins Endurance exercise has been consistently shown to increase serum levels of 13-endorphinl-4. Limited research examining the effects of resistance exercise, however, has resulted in equivocal findings. Elliot Generalizations from the studies noted above are further complicated by differences in methodology such as lifting protocol and the duration of recovery intervals. The purpose of the present study was to examine further the effects of a controlled protocol of resistance (weightlifting) on plasma 13-endorphin immunoreactivity. MethodTen men recreational weightlifters (mean(s.e.) age 20.7(0.56) years; mean(s.e.) weight 79.9(2.2) kg; mean(s.e.) height 182.3(2.5) cm) and ten women basketball players (mean(s.e.) age 19.4(0.41) years; mean(s.e.) weight 68.6(1.7) kg; mean(s.e.) height 176.2(2.0) cm) volunteered to participate in the study. Each subject signed an informed consent document approved by the Human Investigation Committee of the University of Richmond. The participants were briefed on sampling and testing procedures after which blood was sampled from the group by venipuncture, placed on ice, then plasma was separated by centrifugation at 1500g for 10 min in a refrigerated centrifuge. The plasma was then stored in 1-ml aliquots at -70'C. Immediately after the first venipuncture, each subject began participation in a series of isotonic exercises using Nautilus (Lake Helen, Florida) resistance machines. This equipment was used (as opposed to 'free' weights) in order to standardize muscle movements and to control the duration of recovery intervals between exercises. The exercise session consisted of three sets of eight repetitions at 80% of one repetition maximum (1-RM) (or until muscular failure occurred) for each of the following exercises: (1) bench press; (2) lateral pull-downs; (3) seated arm curls; and (4) military press. One repetition maximum (1-RM) for eac...
Research examining the relationship between beta-endorphin immunoreactivity and affect has resulted in equivocal findings. To examine this relationship further, 10 male and 10 female college-age students participated in a controlled free-weight exercise session. Blood plasma samples were procured both prior to and following the exercise bout and beta-endorphin levels were determined by immunoassay. Analysis indicated that plasma beta-endorphin levels following exercise were significantly decreased from pre-exercise levels. Pearson correlations showed no significant relationship between pre- or postexercise plasma beta-endorphins and either total mood disturbance or Profile of Mood States subscores. The data support previous failure of resistance exercise to produce an increase in beta-endorphin immunoreactivity as well as the lack of a significant relationship between affect and the beta-endorphin response to exercise.
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