Evaluation of salivary α-amylase and immunoglobulin A responses after endurance exercise in adolescent males and females with similar aerobic fitness.

The objective of this study was to clarify whether there are sex-specific differences in salivary α-amylase and immunoglobulin A responses following acute endurance exercise in adolescent males and females with equivalent cardiorespiratory fitness levels. Twenty-six aerobically trained adolescent males and females with similar training status were enrolled in this study. Each individual executed a 1-h prolonged cycling exercise corresponding to a constant power output at 65% of peak oxygen uptake. Unstimulated whole salivary samples were taken with the passive drooling method at the 10-min period before and after exercise for the determination of salivary responses [α-amylase, immunoglobulin A, total protein and flow rate]. Salivary α-amylase activity, immunoglobulin A concentration and total protein concentration were significantly augmented immediately after acute endurance exercise. Regarding sex differences, only the salivary flow rate was significantly lower in females than in males. The findings of the present study imply that adolescent males and females appear to have similar salivary responses after acute endurance exercise, as represented by salivary α-amylase activity and immunoglobulin A concentration in connection with total protein concentration and salivary flow rate, when they are matched for peak oxygen uptake relative to fat-free body mass.

Effects of Playing Position on Hydration Status in Collegiate Marching Band Musicians.

OBJECTIVE: Marching band musicians often endure prolonged daily practices in warm-hot outdoor environments. Evaluation of hydration status by instrument position can shed light on health-related issues for these performers. The objective of this study was: a) to determine the effects of playing position on hydration status based on urinary biomarkers (urinary specific gravity and urinary osmolality) before and after marching band practice, and b) to evaluate the relation of hydration status with body mass change and fluid consumption for all playing positions. METHODS: Fifty-eight collegiate marching band players participated in this study, involving five playing positions: band pit (n=10), baritone and euphonium (n=12), snare drum (n=13), trumpet (n=12), and tuba (n=11). All participants performed their own routine marching band practice, which lasted a total of 6 hrs on 1 day. Each individual consumed ad libitum commercially available carbohydrate-electrolyte solution during the practice. To determine hydration status, urine samples were collected before and after practice for analysis of urinary specific gravity and urinary osmolality. Body weight and total fluid intake were also assessed pre- and post-exercise. RESULTS: There were no significant effects for playing position and time or interaction concerning the levels of urinary osmolality and specific gravity after practice. CONCLUSIONS: Our main findings suggest that hydration status may be similar among the different playing positions following prolonged practice in the outdoor environment.

Effects of repeated bouts of long-duration endurance exercise on muscle and urinary levels of 8-hydroxy-2'-deoxyguanosine in moderately trained cyclists.

The purpose of this study was to determine the effects of repeated bouts of long-duration endurance exercise on both muscle and urinary levels of oxidative DNA damage in moderately trained individuals. Seven moderately trained male cyclists participated in this study. All participants repeated two sessions consisting of a 5-h cycling period (equivalent to approximately 52%[Formula: see text]O2peak) followed by a 15-h rest, then a 40-km time trial. During the sessions, participants were instructed to take water ad libitum and to consume a standard sports drink consisting of 0.12 g·kg(-1) body weight·hr(-1) of carbohydrates. For each session, 24 h urine output was collected on the day before the 5-h exercise, and also between the 5-h exercise and 40-km time trial, in addition to between days 1-5 post-exercise. Subsequently, muscle and urinary levels of 8-hydroxy-2'- deoxyguanosine (8-OHdG) were determined using high performance liquid chromatography with electrochemical detection. No significant alterations were observed between two sessions at the muscle or urinary levels of 8-OHdG. These results suggest that repeated bouts of exercise with a 7-day washout period may not lead to an accumulation of DNA damage products after a second 5-h stationary cycling bout.

Assessment of whole-body DNA oxidation following prolonged exercise in adolescent males and females matched for aerobic capacity.

OBJECTIVE: The purpose of this study was to investigate the effects of moderately extended cycling exercise on oxidative DNA damage (accounted for by urinary 8-hydroxy-2´-deoxyguanosine) in adolescent males and females matched for aerobic capacity. MATERIALS AND METHODS: Twenty-nine aerobically active adolescent males and females matched for peak oxygen uptake (VO2peak) relative to fat free mass (ml/kg FFM/min) participated in this study. Two-hour urinary samples were taken at three time points before (-2-0h), immediately (0-2h) after and 24-26 h after 60 min of cycling exercise at 65%VO2peak, followed by the analysis of urinary 8-OHdG (a potential marker of whole-body DNA damage and repair) determined with high performance liquid chromatography with electrochemical detection. RESULTS: The two-way (time x sex) analysis of variance demonstrated no significant main effects for time, sex or interaction regarding urinary 8-hydroxy-2´-deoxyguanosine level following moderate-intensity endurance exercise. CONCLUSIONS: These results of the present study suggest that no detrimental DNA damage can be observed after moderately prolonged exercise in aerobically fit males and females, potentially because of the enhanced antioxidant defense responses. Furthermore, the endurance-trained adolescent males and females appear to have similar DNA oxidation responses at the whole-body level when normalized to peak oxygen uptake relative to fat free mass.

Short-term unilateral leg immobilization alters peripheral but not central arterial structure and function in healthy young humans.

Short-term leg immobilization is an acute model of inactivity, which induces vascular deconditioning. The present study was conducted to determine if short-term leg immobilization induced alterations in central and peripheral conduit artery structure (diameter and compliance), function (resting blood flow and mean wall shear rate), and peripheral flow-mediated dilation. Healthy participants (n = 7 women and n = 8 men) were studied before and after 12 days of unilateral leg immobilization. Carotid artery structure and function were unaltered with immobilization indicating that the unilateral immobilization did not have a detectable effect on this representative central artery. In contrast, peripheral measures of arterial structure at the common femoral and popliteal arteries showed significant reductions in both the immobilized and non-immobilized limbs but to a greater extent in the immobilized limbs. Specifically, femoral and popliteal artery compliance and femoral artery diameter were reduced in both the immobilized and the non-immobilized limb (p < 0.05) while popliteal artery diameter was reduced only in the immobilized leg. Popliteal artery flow-mediated dilation, an indicator of peripheral artery function, was increased in the immobilized limb, which parallels reports in paralyzed limbs of spinal-cord-injured individuals. The time course of vascular alterations with inactivity likely follows a sequence of adaptations in arterial structure and function reflecting differing initial flow patterns, and arterial wall composition, and diverse hemodynamic stimuli within different blood vessels.

Concurrent evaluation of salivary and urinary α-amylase activity following prolonged exercise with or without carbohydrate solution in aerobically active men.

OBJECTIVE: The purpose of this study was to determine the effects of 2-h moderately prolonged exercise with carbohydrate intake or water placebo on salivary and urinary α-amylase isoenzyme activity in trained men. MATERIALS AND METHODS: Eleven aerobically fit men participated in this study. On two different occasions, participants performed 2-h cycling corresponding to a constant power output at 60% peak oxygen uptake. The study design involved a random order, placebo-controlled and cross-over assignment. Participants consumed either 6.2% carbohydrate solution or water placebo every twenty minutes thereafter (2 ml/kg body mass) over 2-h endurance exercise. Unstimulated whole salivary samples were collected using the passive drooling method at the 10-min period before and after exercise for the quantification of salivary α-amylase, immunoglobulin A (IgA) and total protein. Two-hour urinary samples were obtained at three time points before (-2-0h), immediately (0-2 h) after and 24-26 h after exercise for the analysis of α-amylase isoenzyme activity (pancreas- and saliva-derived types). RESULTS: The activity of α-amylase in saliva and urine was significantly increased in connect with salivary total protein concentration immediately after moderately long-lasting exercise, but salivary IgA concentration was not statistically significant with or without exogenous carbohydrate intake. CONCLUSION: These findings suggest that 2-h moderate exercise appears to lead to the enhanced α-amylase activity in saliva and urine regardless of exogenous carbohydrate availability, demonstrating enhanced mucosal immune defense.

Assessment of urinary protein composition in response to consecutive days of wildland firefighting.

The purpose of this study was to examine the pattern of urinary protein excretion induced by 3 consecutive days of wildland firefighting. Eighteen male active-duty military personnel served as the participants. All testing on the 3 consecutive days was conducted at a Northwestern USA fire camp. All participants consumed military-based foods containing 2620-2864 kcal/day. The work activity was evaluated with an accelerometer in association with body weight and hydration markers over the experimental period. Urinary samples were collected pre and post workshift on days 1 and 3 to assess glomerular and tubular protein excretion (total protein, albumin, ß2-microglobulin, N-acetyl-ß-d-glucosaminidase and creatinine). The urinary levels of glomerular and tubular protein were not significantly different. The main findings of the present study indicate that similar alterations of urinary protein composition can be observed over consecutive days of wildland firefighting, which appears to be dependent on intensity rather than total work output.

Forced ventilation increases variability of isometric finger forces.

The study aimed to assess the effects of forced ventilation on variability of the index finger force at the submaximal levels. Fourteen (6 men, 8 women) healthy subjects were instructed to perform self-initiated forced inspiration and forced expiration, the Valsalva maneuver and normal breathing while sustaining 15%, 30%, and 45% of maximal voluntary contraction (MVC) by the index finger. Standard deviation (S.D.) of finger forces increased significantly with the level of force. At each level of force, the mean force was not significantly changed under different breathing conditions. S.D. and coefficient variation (CV) during forced inspiration and expiration was significantly greater than S.D. and CV during normal breathing and the Valsalva maneuver at each force level. No significant differences in S.D. and CV were found between forced inspiration and expiration or between normal breathing and the Valsalva maneuver. Force variability synchronized with the initiation of forced inspiration and expiration, but not with the ventilation data during the Valsalva maneuver or normal breathing. These findings demonstrate clearly that finger force variability is affected by specific ventilation patterns at submaximal force levels. Therefore, assessment of force variability should consider the influence of ventilation.

Sex-based differences in skeletal muscle function and morphology with short-term limb immobilization.

The purpose of this study was to determine the effects of short-term (14-day) unilateral leg immobilization using a simple knee brace (60 degree flexion)- or crutch-mediated model on muscle function and morphology in men (M, n = 13) and women (W, n = 14). Isometric and isokinetic (concentric-slow, 0.52 rad/s and fast, 5.24 rad/s) knee extensor peak torque was determined at three time points (Pre, Day-2, and Day-14). At the same time points, magnetic resonance imaging was used to measure the cross-sectional area of the quadriceps femoris and dual-energy X-ray absorptiometry scanning was used to calculate leg lean mass. Muscle biopsies were taken from vastus lateralis at Pre and Day-14 for myosin ATPase and myosin heavy chain analysis. Women showed greater decreases (Pre vs. Day-14) compared with men in specific strength (N/cm2) for isometric [M = 3.1 +/- 13.3, W = 17.1 +/- 15.9%; P = 0.055 (mean +/- SD)] and concentric-slow (M = 4.7 +/- 11.3, W = 16.6 +/- 18.4%; P < 0.05) contractions. There were no immobilization-induced sex-specific differences in the decrease in quadriceps femoris cross-sectional area (M = 5.7 +/- 5.0, W = 5.9 +/- 5.2%) or leg lean mass (M = 3.7 +/- 4.2, W = 2.7 +/- 2.8%). There were no fiber-type transformations, and the decreases in type I (M = 4.8 +/- 5.0, W = 5.9 +/- 3.4%), IIa (M = 7.9 +/- 9.9, W = 8.8 +/- 8.0%), and IIx (M = 10.7 +/- 10.8, W = 10.8 +/- 12.1%) fiber areas were similar between sexes. These findings indicate that immobilization-induced loss of knee extensor muscle strength is greater in women compared with men despite a similar extent of atrophy at the myofiber and whole muscle levels after 14 days of unilateral leg immobilization. Furthermore, we have described an effective and safe knee immobilization method that results in reductions in quadriceps muscle strength and size.

Little change in markers of protein breakdown and oxidative stress in humans in immobilization-induced skeletal muscle atrophy.

A number of studies in rodents suggest that disuse atrophy results from a large increase in proteolysis affected by, or accompanying, increased oxidative stress. Little information is available, however, about the effects of immobilization on markers of muscle protein breakdown and oxidative stress in humans. Therefore, the purpose of this investigation was to measure markers of breakdown or oxidative stress in subjects who underwent 14 days of knee-brace-mediated immobilization. Vastus lateralis samples taken from 21 young subjects before, and 2 days and 14 days after, single leg immobilization were measured for ubiquitin-protein conjugates, caspase 3/7 activity, the 14-kDa caspase-3 cleaved actin fragment, 4-hydroxy-2-nonenal (4-HNE) adducts, and protein carbonyls. Quadriceps cross-sectional area decreased by 5.7% +/- 1.1% (p < 0.0001) following immobilization. Ubiquitin-protein conjugates were elevated at 2 days of immobilization (12%, p < 0.05) but were not different from baseline at 14 days. Levels of the 14-kDa actin fragment and caspase 3/7 activity did not change over the immobilization period. The oxidative stress markers, 4-HNE adducts and protein carbonyls, did not change at any time point. These static measures of breakdown and oxidative modification suggest that a small increase in protein ubiquitination occurs early (2 days), but elevations in ubiquitinated or oxidatively modified proteins are not sustained during the later phase (14 days) of uncomplicated disuse atrophy in humans, suggesting that these pathways are not playing a major role in simple disuse-induced atrophic loss of protein mass.

Limb immobilization induces a coordinate down-regulation of mitochondrial and other metabolic pathways in men and women.

Advancements in animal models and cell culture techniques have been invaluable in the elucidation of the molecular mechanisms that regulate muscle atrophy. However, few studies have examined muscle atrophy in humans using modern experimental techniques. The purpose of this study was to examine changes in global gene transcription during immobilization-induced muscle atrophy in humans and then explore the effects of the most prominent transcriptional alterations on protein expression and function. Healthy men and women (N = 24) were subjected to two weeks of unilateral limb immobilization, with muscle biopsies obtained before, after 48 hours (48 H) and 14 days (14 D) of immobilization. Muscle cross sectional area (approximately 5%) and strength (10-20%) were significantly reduced in men and women (approximately 5% and 10-20%, respectively) after 14 D of immobilization. Micro-array analyses of total RNA extracted from biopsy samples at 48 H and 14 D uncovered 575 and 3,128 probes, respectively, which were significantly altered during immobilization. As a group, genes involved in mitochondrial bioenergetics and carbohydrate metabolism were predominant features at both 48 H and 14 D, with genes involved in protein synthesis and degradation significantly down-regulated and up-regulated, respectively, at 14 D of muscle atrophy. There was also a significant decrease in the protein content of mitochondrial cytochrome c oxidase, and the enzyme activity of cytochrome c oxidase and citrate synthase after 14 D of immobilization. Furthermore, protein ubiquitination was significantly increased at 48 H but not 14 D of immobilization. These results suggest that transcriptional and post-transcriptional suppression of mitochondrial processes is sustained throughout 14 D of immobilization, while protein ubiquitination plays an early but transient role in muscle atrophy following short-term immobilization in humans.

Substrate oxidation during incremental arm and leg exercise in men and women matched for ventilatory threshold.

The aim of this study was to determine the variations in substrate utilization between men and women matched for ventilatory threshold (Tvent) during incremental arm cranking and leg cycling exercise at 70, 85, 100 and 115% of the mode-specific Tvent. Recreationally active men (n=12) and women (n=10) with similar values for percentage of peak oxygen consumption at Tvent participated in the study. Ventilatory equivalence, excess CO2 and modified V-slope methods were used concurrently to determine Tvent. The participants performed 5 min of exercise at each of 70, 85, 100 and 115% Tvent during both arm cranking and leg cycling exercise. The females were tested during the early follicular phase for all trials. A two-way mixed-design analysis of variance was performed to test for differences between the sexes. When carbohydrate and fat oxidation were expressed relative to total fat-free mass, carbohydrate oxidation during arm cranking and leg cycling was significantly higher in men than women at each percentage of Tvent. In contrast, women showed significantly higher fat oxidation across intensities during both arm cranking and leg cycling. Our results suggest that when substrate utilization is expressed relative to total fat-free mass, women appear to maintain a higher rate of fat and lower rate of carbohydrate oxidation than men during both incremental arm cranking and leg cycling exercise relative to Tvent.

Oxidative stress and antioxidant enzyme upregulation in SOD1-G93A mouse skeletal muscle.

Amyotrophic lateral sclerosis (ALS) is caused by motor neuron loss in the spinal cord, but the mechanisms responsible are not known. Ubiquitous transgenic overexpression of copper/zinc superoxide dismutase (SOD1) mutations causing familial ALS (SOD1mut) leads to an ALS phenotype in mice; however, restricted expression of SOD1mut in neurons alone is not sufficient to cause this phenotype, suggesting that non-neuronal SOD1mut expression is also required for disease manifestation. Recently, several investigators have suggested that SOD1mut -mediated oxidative stress in skeletal muscle may contribute to ALS pathogenesis. The purpose of this study was to examine oxidative stress and antioxidant enzyme adaptation in 95-day-old SOD1-G93A skeletal muscle. We observed significant elevations in both malondialdehyde (22% and 31% in red and white gastrocnemius, respectively) and protein carbonyls (53% in red gastrocnemius) in SOD1-G93A mice. Copper/zinc SOD activity was higher in red and white SOD1-G93A gastrocnemius (7- and 10-fold, respectively), as was manganese SOD (4- and 5-fold, respectively) and catalase (2- and 2.5-fold, respectively). Taken together, our data demonstrate oxidative stress and compensatory antioxidant enzyme upregulation in SOD1-G93A skeletal muscle.

Nutritional therapy improves function and complements corticosteroid intervention in mdx mice.

Corticosteroid therapy for Duchenne muscular dystrophy is effective but associated with long-term side effects. To determine the potential therapeutic benefit from four nutritional compounds (creatine monohydrate, conjugated linoleic acid, alpha-lipoic acid, and beta-hydroxy-beta-methylbutyrate) alone, in combination, and with corticosteroids (prednisolone), we evaluated the effects on several variables in exercising mdx mice. Outcome measures included grip strength, rotarod performance, serum creatine kinase levels, muscle metabolites, internalized myonuclei, and retroperitoneal fat pad weight. In isolation, each nutritional treatment showed some benefit, with the combination therapy showing the most consistent benefits. Prednisolone and the combination therapy together provided the most consistent evidence of efficacy; increased peak grip strength (P < 0.05), decreased grip strength fatigue (P < 0.05), decreased number of internalized myonuclei (P < 0.01), and smaller retroperitoneal fat pad stores (P < 0.001). This study provided evidence for therapeutic benefit from a four-compound combination therapy alone, and in conjunction with corticosteroids in the mdx model of DMD.

Effects of high-intensity endurance exercise training in the G93A mouse model of amyotrophic lateral sclerosis.

The G93A transgenic mouse has a mutation in copper/zinc superoxide dismutase (CuZnSOD) that results in oxidative stress and motor neuron loss. Endurance exercise training is known to increase antioxidant capacity in skeletal muscle. Therefore, we hypothesized that endurance training may extend onset of disease or survival in the G93A mouse. We examined the effects of high-intensity endurance exercise training (45 min/day, 5 times/week, progressive increase from 9 to 22 m/min) on disease onset and survival in G93A mice. Endurance training did not affect clinical onset, although it hastened death in male mice (P < 0.05). Endurance-trained males had a statistically significant decrease in rotarod performance at 112 days (P < 0.05), whereas sedentary males decreased at 119 days (P < 0.05). Endurance-trained and sedentary females decreased at 126 days and 129 days, respectively (P < 0.05). Female mice lived longer than males (P < 0.05), and there was a trend for hastened clinical onset in males (P = 0.062). We conclude that high-intensity endurance exercise training does not affect onset of clinical symptoms in G93A mice but hastens a decrease in motor performance and death following onset of clinical symptoms in male mice only. In light of a recent report describing increased survival following low-intensity endurance training, it appears that training intensity is an important determinant of survival in the G93A mouse.