Hr Post Exercise Research Articles

Postexercise Glycogen Recovery and Exercise Performance is Not Significantly Different Between Fast Food and Sport Supplements.

A variety of dietary choices are marketed to enhance glycogen recovery after physical activity. Past research informs recommendations regarding the timing, dose, and nutrient compositions to facilitate glycogen recovery. This study examined the effects of isoenergetic sport supplements (SS) vs. fast food (FF) on glycogen recovery and exercise performance. Eleven males completed two experimental trials in a randomized, counterbalanced order. Each trial included a 90-min glycogen depletion ride followed by a 4-hr recovery period. Absolute amounts of macronutrients (1.54 ± 0.27 g·kg-1 carbohydrate, 0.24 ± 0.04 g·kg fat-1, and 0.18 ±0.03g·kg protein-1) as either SS or FF were provided at 0 and 2 hr. Muscle biopsies were collected from the vastus lateralis at 0 and 4 hr post exercise. Blood samples were analyzed at 0, 30, 60, 120, 150, 180, and 240 min post exercise for insulin and glucose, with blood lipids analyzed at 0 and 240 min. A 20k time-trial (TT) was completed following the final muscle biopsy. There were no differences in the blood glucose and insulin responses. Similarly, rates of glycogen recovery were not different across the diets (6.9 ± 1.7 and 7.9 ± 2.4 mmol·kg wet weight- 1·hr-1 for SS and FF, respectively). There was also no difference across the diets for TT performance (34.1 ± 1.8 and 34.3 ± 1.7 min for SS and FF, respectively. These data indicate that short-term food options to initiate glycogen resynthesis can include dietary options not typically marketed as sports nutrition products such as fast food menu items.

The Influence of Oral L-Glutamine Supplementation on Muscle Strength Recovery and Soreness Following Unilateral Knee Extension Eccentric Exercise

The study aimed to examine the effects that L-glutamine supplementation has on quadriceps muscle strength and soreness ratings following eccentric exercise. It was hypothesized that glutamine ingestion would quicken the recovery rate of peak force production and decrease muscle soreness ratings over a 72-hr recovery period. Sixteen healthy participants (8♀/8♂; 22 ± 4 years) volunteered in a double-blind, randomized, placebo-controlled crossover study. Supplement conditions consisted of isoenergetic placebo (maltodextrin, 0.6 g·kg-1·day-1) and L-glutamine (0.3 g·kg-1·day-1 + 0.3 g·kg-1·day-1 maltodextrin) ingestion once per day over 72 hr. Knee extensor peak torque at 0°, 30°, and 180° per second and muscle soreness were measured before, immediately following, 24, 48, and 72 hr posteccentric exercise. Eccentric exercise consisted of 8 sets (10 repetitions/set) of unilateral knee extension at 125% maximum concentric force with 2-min rest intervals. L-glutamine resulted in greater relative peak torque at 180°/sec both immediately after (71 ± 8% vs. 66 ± 9%), and 72 hr (91 ± 8% vs. 86 ± 7%) postexercise (all, p < .01). In men, L-glutamine produced greater (p < .01) peak torques at 30°/ sec postexercise. Men also produced greater normalized peak torques at 30°/sec (Nm/kg) in the L-glutamine condition than women (all, p < .05). In the entire sample, L-glutamine resulted in lower soreness ratings at 24 (2.8 ± 1.2 vs. 3.4 ± 1.2), 48 (2.6 ± 1.4 vs. 3.9 ± 1.2), and 72 (1.7 ± 1.2 vs. 2.9 ± 1.3) hr postexercise (p < .01). The L-glutamine supplementation resulted in faster recovery of peak torque and diminished muscle soreness following eccentric exercise. The effect of L-glutamine on muscle force recovery may be greater in men than women.

Acute Hypoxia and Exercise-Induced Blood Oxidative Stress

Hypoxic exercise is characterized by workloads decrements. Because exercise and high altitude independently elicit redox perturbations, the study purpose was to examine hypoxic and normoxic steady-state exercise on blood oxidative stress. Active males (n = 11) completed graded cycle ergometry in normoxic (975 m) and hypoxic (3,000 m) simulated environments before programing subsequent matched intensity or workload steady-state trials. In a randomized counterbalanced crossover design, participants completed three 60-min exercise bouts to investigate the effects of hypoxia and exercise intensity on blood oxidative stress. Exercise conditions were paired as such; 60% normoxic VO(2)peak performed in a normoxic environment (normoxic intensity-normoxic environment, NI-NE), 60% hypoxic VO(2)peak performed in a normoxic environment (HI-NE), and 60% hypoxic VO(2)peak performed in a hypoxic environment (HI-HE). Blood plasma samples drawn pre (Pre), 0 (Post), 2 (2HR) and 4 (4HR) hr post exercise were analyzed for oxidative stress biomarkers including ferric reducing ability of plasma (FRAP), trolox equivalent antioxidant capacity (TEAC), lipid hydroperoxides (LOOH) and protein carbonyls (PCs). Repeated-measures ANOVA were performed, a priori significance of p ≤ .05. Oxygen saturation during the HI-HE trial was lower than NI-NE and HI-NE (p < .05). A Time × Trial interaction was present for LOOH (p = .013). In the HI-HE trial, LOOH were elevated for all time points post while PC (time; p = .001) decreased post exercise. As evidenced by the decrease in absolute workload during hypoxic VO(2)peak and LOOH increased during HI-HE versus normoxic exercise of equal absolute (HI-NE) and relative (NI-NE) intensities. Results suggest acute hypoxia elicits work decrements associated with post exercise oxidative stress.

Fish Oil Supplementation Reduces Markers of Oxidative Stress But Not Muscle Soreness After Eccentric Exercise

Due to the potential anti-inflammatory properties of fish-derived long chain n-3 fatty acids, it has been suggested that athletes should regularly consume fish oils-although evidence in support of this recommendation is not clear. While fish oils can positively modulate immune function, it remains possible that, due to their high number of double bonds, there may be concurrent increases in lipid peroxidation. The current study aims to investigate the effect of fish oil supplementation on exercise-induced markers of oxidative stress and muscle damage. Twenty males underwent a 6-week double-blind randomized placebo-controlled supplementation trial involving two groups (fish oil or placebo). After supplementation, participants undertook 200 repetitions of eccentric knee contractions. Blood samples were taken presupplementation, postsupplementation, immediately, 24, 48, and 72 hr postexercise and muscle soreness/maximal voluntary contraction (MVC) assessed. There were no differences in creatine kinase, protein carbonyls, endogenous DNA damage, muscle soreness or MVC between groups. Plasma thiobarbituric acid reactive substances (TBARS) were lower (p < .05) at 48 and 72 hr post exercise and H2O2 stimulated DNA damage was lower (p < .05) immediately postexercise in the fish oil, compared with the control group. The current study demonstrates that fish oil supplementation reduces selected markers of oxidative stress after a single bout of eccentric exercise.

Abstract 270: Self-Efficacy and Cardiovascular Health in 6 th Graders: An Insight from Project Healthy Schools

Background: Behaviors such as regular physical activity are associated with improved self-esteem among children and adolescents. However, associations between wellness behaviors (including diet) and both self-esteem and leadership among middle-school children have not been well studied. Methods: Data were collected from middle-school children enrolled in Project Healthy Schools, a school-based wellness program. Baseline data included self-reported information on diet, physical activity, and questions on self-efficacy for empathy and leadership. Physiologic data included body mass index (BMI), blood pressure (BP), heart rates (resting and one minute post exercise protocol), non-fasting lipids, glucose. Respondents were grouped into tertiles based on survey items related to empathy. Results: Data from 1,079 6 th graders (mean age 11.6 years) were included. Students in the low tertile for empathy had higher BMIs than students in the middle/higher tertiles (p=0.03) with no difference between tertiles for lipids (including total cholesterol, HDL-cholesterol, triglycerides, and LDL-cholesterol). A trend towards higher glucose levels was observed among children in the lower tertile compared to the other tertiles (101.2, 99.4, and 99.5 for tertile 1, 2, and 3 respectively, p = 0.58). A similar trend was observed for systolic BP (p = 0.52) but not diastolic BP, resting HR or HR post exercise. No difference was observed between self-efficacy for leadership and any of the physiologic parameters. Those in the highest tertile for leadership self-efficacy were more likely to be physically active, averaging 4.71 (± 2.11) days of vigorous activity; a similar trend was noted for empathy. Moderate exercise (≥ 30 minutes per day) and team sports positively correlated with empathy and leadership. Conclusions: Among middle-school students, measures of empathy and leadership were associated with higher levels of physical activity and participation in team sports; but not with physiologic parameters. Given that higher levels of empathy and leadership were associated with lower BMI, it is possible that programs which improve leadership skills and promote empathy can improve healthy lifestyle habits.

Effect of a High and Low Dose of Caffeine on Antigen-Stimulated Activation of Human Natural Killer Cells After Prolonged Cycling

This study investigated the effect of a high and low dose of caffeine on antigen-stimulated natural killer (NK) cell (CD3- CD56+) activation after prolonged, strenuous cycling, as assessed by the early-activation molecule CD69. In a randomized crossover design, 12 healthy male endurance-trained cyclists cycled for 90 min at 70% VO2peak 60 min after ingesting either 0 (PLA), 2 (2CAF), or 6 (6CAF) mg/kg body mass of caffeine. Whole blood was stimulated with Pediacel (5 in 1) vaccine. A high dose of caffeine (6CAF) increased the number of CD3-CD56+ cells in the circulation immediately postexercise compared with PLA (p < .05). For both 2CAF and 6CAF, the geometric mean fluorescence intensity (GMFI) of CD69+ expression on unstimulated CD3-CD56+ cells was significantly higher than with PLA (both p < .05). When cells were stimulated with antigen, the GMFI of CD69 expression remained significantly higher with 2CAF than with PLA 1 hr postexercise (p < .05). Although not achieving statistical significance, 6CAF also followed a similar trend when stimulated (p = .09). There were no differences in GMFI of CD69 expression between 2CAF and 6CAF. These results suggest that a high (6 mg/kg) dose of caffeine was associated with the recruitment of NK cells into the circulation and that both a high and low (2 mg/kg) dose of caffeine increased unstimulated and antigen-stimulated NK-cell activation 1 hr after high-intensity exercise. Furthermore, there does not appear to be a dose-dependent effect of caffeine on NK-cell activation 1 hr after prolonged intensive cycling.

Effects Of Niacin And Aerobic Exercise On Glucose, Insulin, And C-peptide Profiles In Postmenopausal Women

The effects of niacin and exercise on glucose metabolism are well documented in men and premenopausal women; however, no studies have been conducted with postmenopausal women. PURPOSE: To determine the effects of niacin and a single bout of aerobic exercise on glucose, insulin, and C-peptide profiles in sedentary, postmenopausal women. METHODS: Seventeen sedentary, postmenopausal women (mean ± SD; 57 ± 7.5 years; 160.1 ± 7 cm; 77.2 ± 14.8 kg, 47.0 ± 6.2 % body fat) served as participants. All participants were randomly assigned to the resting or exercise trial without niacin followed by the with-niacin trial (1000 mg/day of extended release niacin for 4 weeks). The exercise trial consisted of treadmill walking at 60% heart rate reserve until 400 kcal were expended. Blood samples collected 24 hr post rest and exercise trials were analyzed for changes in glucose, insulin, and C-peptide. Data were analyzed using a 2 × 2 repeated measures analysis of variance (ANOVA) and the Bonferroni adjustment served as the post hoc test. The level of statistical significance was set at p <.05. RESULTS: There was no significant interaction of exercise with niacin for glucose, insulin, and C-peptide, nor was there a main effect of exercise. There was a significant main effect for niacin as mean glucose, insulin, and C-peptide values all significantly increased with niacin use; glucose increased 10.6%, from 95.03 ± 10.67 mg/dL to 105.07 ± 13.56 mg/dL; insulin increased 61.8%, from 16.98 ± 12.49 μU/mL to 27.48 ± 14.84 μU/mL; and C-peptide increased 46.1%, from 1.65 ± 0.75 ng/mL to 2.41 ± 0.97 ng/mL. CONCLUSION: Although niacin was generally well tolerated by the participants, given its adverse effects on glucose, insulin, and C-peptide profiles, the use of niacin in sedentary, postmenopausal women should be done so with caution and under medical supervision until more comprehensive investigations consisting of niacin alone or with aerobic exercise are conducted.

L-Cysteine’s Effect on Modulated Rat Brain Enzymes with Forced Swimming

Forced exercise is associated with oxidative stress, and L-cysteine (L-cys) administration reduces free-radical production. To investigate whether L-cys (5 mg/kg) intraperitoneal administration can ameliorate modulated total antioxidant status (TAS), protein concentration, and the activities of acetylcholinesterase (AChE), (Na+,K+)-ATPase, and Mg2+-ATPase in rat brain after 2 and 3 hr of forced swimming. TAS, protein, and enzyme activities were measured spectrophotometrically before and after 2 and 3 hr of exercise without or with L-cys administration. TAS concentration (55.6 +/- 1.5 vs. 42.1 +/- 1.0 vs. 37.4 +/- 1.2 micromol/L, p < .001), protein concentration (5.68 +/- 0.36 vs. 5.40 +/- 0.18 vs. 4.01 +/- 0.16 mg/ml, p < .01), and AChE activity (0.89 +/- 0.05 vs. 0.61 +/- 0.04 vs. 0.48 +/- 0.03 DeltaOD/min x mg protein, p < .001) were significantly reduced, whereas Na+,K+-ATPase (6.00 +/- 0.36 vs. 10.44 +/- 1.04 vs. 11.90 +/- 1.21 micromol phosphorus inorganic/hr x mg protein, p < .001) and Mg2+-ATPase activity (7.20 +/- 0.65 vs. 10.88 +/- 1.08 vs. 11.55 +/- 1.22 mmol phosphorus inorganic/hr x mg protein, p < .001) were statistically significantly increased after 2 and 3 hr of forced exercise. Post-L-cys administration, AChE activity was decreased (0.90 +/- 0.04 vs. 0.47 +/- 0.02 DeltaOD/min x mg protein, p < .001) and remained unaltered (0.64 +/- 0.04 vs. 0.67 +/- 0.04 DeltaOD/min x mg protein, p > .05) 2 and 3 hr postexercise (0.47 +/- 0.02 vs. 0.54 +/- 0.02 DeltaOD/min x mg protein, p > .05). Na+,K+-ATPase was decreased and remained unchanged (1.85 +/- 0.17 vs. 1.77 +/- 0.19 mumol phosphorus inorganic/hr x mg protein, p > .05) 2 and 3 hr postswimming (1.91 +/- 0.19 vs. 2.06 +/- 0.17 mumol phosphorus inorganic/hr x mg protein, p > .05). Mg2+-ATPase activity was similar with L-cys supplementation pre- vs. postswimming. L-cys administration might ameliorate modulated rat brain enzyme activities induced by free-radical production during forced swimming.

Effects Of Breakfast Omission And An Acute Bout Of Exercise On Serum Lipid Concentrations

Low-fat, high- fiber breakfast consumption may help lower serum low-density lipoprotein (LDL) and total cholesterol (TC) measurements as well as help control daily energy intake and insulin sensitivity while moderate exercise is an effective method for increasing high-density lipoprotein (HDL) and decreasing triglyceride (TG) measurements. A combination of these treatments may help maintain optimal blood lipid levels and prevent heart disease. PURPOSE: To observe serum lipid changes immediately and 24 hr after breakfast or no breakfast treatments prior to a 30 min bout of aerobic exercise in middle aged males with no history of dyslipidemia. METHODS: Seven male subjects participated and ranged in age from 30 to 44 years old with an average VO2 peak of 38.66 ml·kg-1·min-1 + 6.09. Data were collected over three testing sessions. During session 1, subjects performed a VO2 peak test and baseline measurements were collected. During sessions 2 and 3, subjects consumed either a low-fat, high-fiber breakfast or no breakfast, both of which were followed by a 30 min bout of exercise at 60% of VO2peak. A fasting blood sample was collected prior to treatment and exercise. Samples were also collected immediately after exercise and 24 hr post exercise. Each subject also reported all dietary intake for 24 hr following both treatments. RESULTS: No significant (p >.05) differences between the breakfast and no breakfast treatments were found for TC, TG, HDL, and LDL when baseline measurements were compared to 24 hr post treatment and exercise measurements. TC, TG, and LDL values were slightly lower 24 hr post exercise than at baseline while HDL values were higher 24 hr after exercise than at baseline when breakfast was omitted. Between the two exercise sessions, no differences were found in 24 hr post exercise macronutrient or total caloric intake. No differences in exercise RER and VO2 were found between treatments. CONCLUSION: A low-fat, high-fiber breakfast in conjunction with 30 min of acute exercise were not sufficient to alter lipid concentrations. Breakfast omission and 30 min of moderate intensity exercise exhibited a trend towards lower cholesterol levels 24 hr post exercise and treatment.

Carbohydrate-Protein Beverage Improves Recovery From Muscle Damage Induced By Downhill Running

Downhill running has been shown to induce muscle fiber damage, delayed-onset muscle soreness, and various functional deficits. Consumption of carbohydrate-protein beverages during or immediately following strenuous exercise have been shown to reduce muscle damage, however its effects on performance recovery following downhill running have yet to be elucidated. PURPOSE: This study examined the effects of CHO+PRO vs. CHO on multiple aspects of muscle recovery following one bout of unaccustomed novel eccentric exercise (downhill running). METHODS: 20 physically active but untrained participants were randomly assigned to either CHO or CHO+PRO (n=10/group). Subjects consumed either 1.2 g·kg-1 CHO (CHO) or 1.2 g·kg-1 CHO + 0.3 g·kg-1 protein (CHO+PRO) daily for 7 days prior to eccentric exercise, and for 2 days following exercise. For eccentric exercise, subjects performed a 30-min downhill run (DHR) at 75% of their maximal heart rate on a -18% gradient. Creatine kinase activity (CK), lower extremity muscle soreness (SOR), and maximal isometric and isokinetic torque, were all assessed prior to 24 hr post, and 48 hr post DHR. Athletic performance was also assessed including 20-m sprint time, gross motor skills, vertical jump, and multistage fitness test prior to DHR and 48 hr post DHR. RESULTS: CK was increased at 24 hr and 48 hr post DHR (P<0.05) but there was no differences between the two treatments. SOR ratings from all three different lower body exercises were significantly elevated over time compared to pre exercise (PRE) and magnitude of hamstring soreness was attenuated at both 24 hr and 48 hr post exercise in the CHO+PRO group (P<0.01). CHO+PRO significantly reduced the deterioration in maximal isokinetic hamstring torque compared to CHO at 24 and 48 hr post DHR (P<0.05) but there were no treatment differences in maximal isometric torque. CHO+PRO treatment also resulted in better 20-m sprint performance 48 hr post DHR. CONCLUSION: The results of this study reveal that short term consumption of CHO+PRO beverage before and after one bout of eccentric exercise can enhance multiple aspects of muscle recovery which may have important implications for athletes and military personnel.

Independent and Combined Effects of Niacin and Exercise on Blood Lipid and Lipoprotein Profiles in Postmenopausal Women

It has been well documented that independently both exercise and niacin positively alter blood lipids and lipoproteins; however, these interventions have not been studied in postmenopausal women. PURPOSE: This study examined the independent and combined effects of niacin and a single bout of exercise on the blood lipid and lipoprotein profiles in postmenopausal women. METHODS: Eighteen sedentary, postmenopausal women (40 - 80 years old), were recruited (mean ± SD; age = 57 ± 6 yrs; height = 161.3 ± 6.7 cm; weight = 75.8 ± 13.9 kg; % body fat = 46.2 ± 6.6 %). The without-niacin (WON) condition was first assigned followed by the with-niacin (WN) condition. The WN condition consisted of ingesting 1,000 mg/day of extended-release niacin for 4 weeks. Rest (R) and exercise (E) trials were randomly assigned within each WON or WN condition. During the E trial treadmill exercise was performed at 60% HRR until 400 kcal were expended. Fasting blood samples were collected immediately before (0 hr) and at 24 and 48 hr post exercise (or rest). All data were reported as mean ± SE. The changes in TC, TG, LDL-C, HDL-C, HDL2-C, and HDL3-C were analyzed using a 2 (WON and WN) × 2 (Rest and Exercise) × 3 (0, 24, and 48 hr) ANOVA with repeated measures. The Bonferroni post-hoc test was applied and the statistical significance was set at p < .05. RESULTS: The concentrations of TC and TG were not altered in reponses to exercise or niacin. However, the niacin treatment without the exercise intervention significantly (p < .05) increased HDL-C (5.4 mg/dl or 12.4 %) and HDL2-C (3.6 mg/dl or 33.3 %) from baseline (43.5 ± 1.7 and 10.8 ± 1.2 mg/dl, respectively). The HDL3-C concentration at EWN-48 hr (35.1 ± 1.1 mg/dl) was significantly (p < .05) higher as compared to EWN-0 hr (33.7 ± 1.0 mg/dl) and EWON-48 hr (32.7 ± 1.3 mg/dl). The LDL-C concentrations at EWN-24 hr (151.7 ± 6.5 mg/dl) and EWN-48 hr (149.9 ± 6.0 mg/dl) were significantly lower than RWN-0 hr (155.9 ± 7.3 mg/dl). CONCLUSION: The niacin treatment (1,000 mg/day) for 4 weeks favorably altered HDL-C, predominantly HDL2-C. However, HDL3-C increased only when a single bout of exericse was perfomed during the niacin treatment.

Modulation of Insulin Signaling via Resistance Exercise

Resistance exercise in rats has been shown to substantially elevate S6K1 phosphorylation for up to 36 hr post exercise. Genetically increasing the activity of S6K1 can alter insulin sensitivity by inhibition of IRS‐1 expression and function. We hypothesized that lengthening contractions would increase S6K1 phosphorylation and down regulate the expression and function of IRS‐1. Wistar rats underwent unilateral lengthening contractions of the right Tibialis Anterior muscles and were collected at 0 mins, 30 mins, 3 hrs, 18 hrs and 48 hrs. S6K1389 phosphorylation was elevated by 751 ± 208 %, 3197 ± 1144 %, 10041 ± 2209 % (p &lt; 0.05), at 0 min, 30 min, 3 hr, respectively. IRS‐1636/639 phosphorylation was significantly increased at 30 mins and 18 hrs by 715 ± 160 % and 170 ± 38 %, respectively. IRS‐1 associated P85 was significantly reduced at 30 min and 3 hrs by 57 ± 7 % and 55 ± 7 %, respectively. Due to the time course of the S6K1389 and IRS‐1636/639 phosphorylation we concluded that S6K1 was the most likely kinase mediating the response. To test this further we pretreated female Wistar rats with rapamycin and collected tissues 30 mins post stimulation. We found that rapamycin reduced the increase in IRS‐1636/639 phosphorylation and partially rescued the reduction in IRS‐1 associated P85. We conclude that increased S6K1 activity after resistance exercise enhances IRS‐1 serine phosphorylation, decreasing IRS‐1 associated P85.

AMPKα2 Activity, Acidosis, and Protein Synthesis in Human Skeletal Muscle Following Resistance Exercise

Resistance exercise is a potent stimulator of muscle protein synthesis. The increase in muscle protein synthesis following resistance exercise is usually detected within 3 hours and remains elevated for up to 48 hours. However, during and immediately after exercise muscle protein synthesis is inhibited. Skeletal muscle AMP-activated protein kinase (AMPK?2) and acidosis have recently been identified as inhibitors of muscle protein synthesis. PURPOSE: To determine if muscle AMPKα2 activity and/or acidosis would be elevated in conditions associated with reduced protein synthesis (i.e., during and immediately post resistance exercise). METHODS: We studied 8 young subjects before, during, and for 2 hours following a bout of resistance exercise (Leg Extensions: 10 sets X 10 repetitions, 70% 1RM). Muscle biopsies were collected from the vastus lateralis before, immediately post exercise, and at 1hr and 2 hr post exercise. We utilized immunoprecipitation methods to measure muscle AMPKα2 activity. Mixed muscle fractional protein synthetic rate (FSR) was measured using stable isotope techniques. RESULTS: Muscle AMPKα2 activity (pmol*g−1*min−1) at baseline was 243 ± 15, increased immediately post exercise (298 ± 23), and remained elevated at 1hr (317 ± 30) and 2hr (321 ± 32) hours post exercise (P <0.05). Preliminary data on muscle protein synthesis (n=3) indicate that muscle FSR was not significantly different from baseline following resistance exercise (P >0.05). Femoral vein lactate increased 14-fold (0.8 ± 0.1 to 11 ± 0.8 mM) during the resistance exercise bout. The average blood lactate during the first hour post exercise remained 3-fold higher (P <0.05) and then returned to baseline values during the second hour post exercise. Femoral vein pH decreased significantly during exercise (7.37 ± 0.01 to 7.17 ± 0.01, P <0.05) and returned to baseline values during the next two hours. CONCLUSIONS: The attenuation of muscle protein synthesis during and immediately after resistance exercise was associated with both increased AMPKα2 activity and acidosis. Further research is required to determine the specific roles of AMPK and acidosis in inhibiting muscle protein synthesis.

Muscle AMPKα2 activity, acidosis, and protein synthesis in men and women following resistance exercise

Basal muscle protein synthesis is not different between men and women. Skeletal muscle AMP-activated protein kinase (AMPKα2) and acidosis have recently been identified as inhibitors of muscle protein synthesis. The purpose of this study was to determine if there were sex-based differences in muscle AMPKα2 activity, acidosis, and protein synthesis in young men and women following a bout of resistance exercise. We report preliminary data obtained in young subjects (4M, 4F) before and after a bout of resistance exercise. Muscle biopsies were collected from the v. lateralis prior to, immediately post exercise, and at 1hr and 2 hr post exercise. We utilized immunoprecipitation methods to measure AMPKα2 activity. Fractional protein synthetic rate was measured using stable isotope techniques. AMPKα2 activity was not different between men and women at any timepoint (P > 0.05). AMPKα2 activity increased by (25 ± 10 %) immediately post exercise, remained elevated at 1hr (33 ± 13%) and 2hr (33 ± 11%) post exercise (P < 0.05). Femoral vein lactate increased to a similar extent in men (0.8 ± 0.2 to 11.9 ± 1.5 mM) and women (0.7 ± 0.1 to 10.1 ± 0.5 mM) during the resistance exercise bout. Blood pH also decreased during exercise (P > 0.05). Lactate and pH returned to baseline similarly in men and women during post exercise recovery (P < 0.05). Muscle protein synthesis was unchanged from baseline following resistance exercise with no sex-based differences (P > 0.05). We conclude that there are no sex-based differences in muscle AMPKα2 activity, acidosis or protein synthesis immediately following a bout of resistance exercise.

Circulating Leukocyte Levels In Response To Active And Passive Cycling In Able Bodied And Spinal Cord Injured

2089 Individuals with spinal cord injury (SCI) lack complete neuroendocrine responses that may influence exercise-induced alterations in immune cell responses. PURPOSE: To examine exercise-induced circulating leukocyte and leukocyte subset responses in individuals with SCI and in able bodied age-matched controls (AB). METHODS: Seven subjects with SCI (3 paraplegic- SCI-PP & 4 quadriplegic-SCI-QP) and seven age-matched AB controls completed 30 min of either active and/or passive cycling. SCI-PP completed 30 min of upper body assisted leg cycling (UBALC) (30 min @ 70% VO2peak) and 30 min of passive leg cycling. SCI-QP completed 30 min of passive leg cycling and 30 min of combined passive arm and leg cycling. AB completed 30 min of active and passive leg cycling. Blood samples were taken before (pre-EXR), after (post-EXR), 2hr post, and 24hr post exercise. Sample analysis included leukocyte total and subset counts. RESULTS: Both active and passive exercise produced alterations in circulating leukocytes and their subsets in all groups that were studied. In SCI-PP, total leukocyte post-EXR UBALC and passive responses were greater (p<0.05) than pre-EXR (14.66 + 4.6 and 8.46 + 1.6 vs. 7.06 + .81 and 6.46 + 1.2 cells x106/ml, respectively). In SCI-QP, passive leg (8.09+1.7 cells x106/ml) and combined arm and leg (12.03 + 1.4 cells x106/ml) cycling produced elevations in total leukocytes compared to pre-EXR with the latter being significantly greater. In AB, active cycling (post-EXR = 9.20+1.8 vs. pre-EXR = 5.14+1.5 cells x106/ml) produced significant elevations, but passive cycling did not (post-EXR = 6.55+1.9 vs. pre-EXR = 5.49+.13 cells x106/ml).group. CONCLUSION: These data indicate that both passive and active exercise produce elevations in circulating leukocytes in individuals with SCI; however, passive responses are blunted. In the SCI-QP group, combined passive arm and leg cycling produced greater elevations than leg cycling alone.

GLUTATHIONE STATUS IN TRAINED AND UNTRAINED HUMANS

Glutathione is a tripeptide that has antioxidant properties and is involved in the regulation of redox sensitive signal transduction. Physical exercise may increase glutathione oxidation in vivo. The ratio of reduced glutathione (GSH) to oxidized glutathione (GSSG) has been used as an indicator for assessing exercise-induced oxidative stress. This study examined the effect a Bruce GTX protocol on the GSH:GSSG ratio in trained (n = 14; VO2peak = 55.7 ± 8.0 ml/kg/min) and untrained (n = 10; VO2peak = 38.6 ± 5.4 ml/kg/min) individuals. Blood samples were collected prior to, immediately post, and 1 hr post exercise. A 2 × 3 repeated measures ANOVA revealed that the pre exercise ratio of GSH:GSSG did not differ between trained and untrained subjects. The GSH:GSSG ratio in trained subjects remained stable after exercise, yet was significantly lower in untrained subjects immediately post exercise (p < 0.05), due to an increase in GSSG concentrations. Values measured 1 hr post exercise, in untrained subjects, returned to pre exercise values (p>0.05), indicating rapid recovery of GSH. These results demonstrate a difference between trained and untrained subjects in response to a GXT protocol and may support the notion that training modifies cellular antioxidant properties. Further studies should focus on the role of the GSH:GSSG ratio in signal transduction and adaptation to training.Table

Serum leptin during recovery following maximal incremental and prolonged exercise.

This study investigated the delayed circulating leptin response to maximal and prolonged treadmill exercise. Six healthy untrained males performed three sessions after an overnight fast: control, maximal exercise, and prolonged exercise at 50% of maximal oxygen consumption. Blood samples were collected prior to exercise, at the end of exercise, and at 60, 120, 180, and 240 min following exercise and control sessions. Blood samples were analyzed for serum leptin, insulin, glucose, free fatty acids, and glycerol. Hemoglobin and hematocrit were measured to correct for plasma volume changes. Resting energy expenditure (REE) and body fat (BF) were also assessed. Immediately at the end of maximal and prolonged exercise, and during the 4 hours of recovery, serum leptin levels did not change significantly compared to their respective baseline values. At 240 min of recovery serum leptin decreased 7% and 9% (p>0.05) from the baseline in the maximal and prolonged sessions, respectively. In the control experiment serum leptin decreased 27% from the baseline at 240 min of the recovery (p < 0.05). No significant differences were found in leptin values between the control and exercise sessions. Control serum leptin was positively correlated (p < 0.05) to BF (r = 0.88) and glucose (r=0.96), and negatively correlated to REE (r= -0.81). In conclusion, maximal or prolonged exercise do not appear to have an influence on circulating serum leptin in the delayed (4 hr) post exercise recovery period.

THE EFFECTS OF EXERCISE DURATION ON POST EXERCISE HYPOTENSION

102 Study 1. Thirteen normotensive volunteers with average baseline blood pressure of 126 / 71 mmHg participated in the study. Participants performed bouts of cycle ergometry for 15, 30 and 45 min at 70% V̇O2 Peak. Blood pressure was monitored by the Finapres method with 2 min windows recorded at rest, 5, 10, 15, 30, 45 and 60 min post exercise. Following exercise, SBP was similar between the three trials and became hypotensive at 5 through 60 min of measurement. DBP was also unaffected by the duration of exercise and was lower than before exercise at 30 through 45 min post exercise. Study 2. Eight borderline hypertensive volunteers with average baseline blood pressure of 133 / 79 mmHg participated in the study. Subjects performed bouts of cycle ergometry for 10 and 30 min at 70% V̇O2 Peak. Following exercise, blood pressure was monitored as in study 1. SBP was similar between both trials and became hypotensive at 5 through 60 minutes post exercise. The largest decrement of SBP was 14 mmHg and occurred 15 min post exercise. DBP was also unaffected by the duration of exercise and was lower than pre-exercise levels at 5 min and again at 15 through 45 min post exercise. MAP also showed significant decrements throughout the entire 1 hr post exercise period by a maximum of 9 mmHg at 15 min post exercise, irrespective of exercise duration. We conclude that moderately intense exercise may be as brief as 10 min in duration in order to elicit a decrease in resting blood pressure and may have potential benefits as a non-pharmacological aid to hypertension. Supported by the Natural Sciences and Engineering Research Council of CANADA

Physiological Response of Scup, Stenotomus chrysops, to a Simulated Trawl Capture and Escape Event

Scup (Stenotomus chrysops) were severely exercised by manual chasing for 6 min, and the clearance of lactate over a 12 hr period was evaluated. Lactate peaked from 0.5 to 1.0 hr following exercise with concentrations ranging from 61.0 to 126.0 mg/dL and returned to rested concentrations within 4 hr post-exercise. Concentrations of lactate in rested fish ranged from 5.2 to approximately 23.0 mg/dL. Fish were observed for 10 days following exercise for delayed mortality. A 100% survival of scup was observed with no significant difference between control and experimental populations.Swimming performance was evaluated for 14.0 to 15.0 cm fork length scup, with a towed stimulus through a still-water circular swimming channel, at prolonged and burst speeds. A maximum sustainable swimming speed of 2.2 BL/sec was observed. Between the speeds of 3.0 and 3.3 BL/sec and 4.4 BL/sec, endurance time significantly decreased with the increase in swimming speed. Blood lactate concentrations were measured at 0.5 and 4.0 hr post exercise, and were used as an indicator of white muscle recruitment. A significant difference was not found between rested and experimental mean lactate concentrations at the maximum sustainable swimming speed of 2.2 BL/sec. White muscle recruitment indicated by increases in lactic acid, was recorded at speeds above the maximum sustained swimming speed, and mean blood lactate concentrations were significantly different within blood sampling times and between swimming speeds.Based on the results of our investigations of lactate recovery in scup following a simulated trawl capture and escape event, we believe that scup interacting with a bottom trawl and subsequently escaping, are physiologically stressed by the event, but recover in less than 6 hr. AU experimentally treated fish survived both exhaustive exercise and prolonged swimming, suggesting encounter mortality is minimal. The results of this study do not address the effects of possible physical damage on escape or the effect of multiple encounters.

Glucose Tolerance Is Improved After Low- and High-Intensity Exercise in Middle-Age Men and Women

We compared the effects of low- and high-intensity exercise on oral glucose tolerance immediately and 24 hr after each exercise bout. Participants were 5 male and 5 female individuals (age 40-48). A fasted, oral glucose tolerance test (OGTT) was conducted several days before the first exercise bout. Glucose and insulin concentrations were determined every 15 min throughout a 2 hr, 75 g OGTT. Immediately after low-intensity exercise, the incremental glucose area under the curve was reduced by 16%, compared to the fasting OGTT (p < .05). This was reduced further (-30%) 24 hr postexercise (p < .05). After high-intensity exercise, similar results were observed, with the incremental glucose area reduced by 14 and 35% immediately and 24 hr postexercise, respectively (p < .05). In conclusion, exercise improves glucose tolerance, this effect is more pronounced 24 hr postexercise, and low- and high-intensity exercise provide similar beneficial effects on glucose tolerance.