Iron status in cyclists during high-intensity interval training and recovery.

The purpose of this study was to examine the effects of a 6 week high-intensity interval training (HIT) program, followed by 2 weeks recovery, on iron status in cyclists. Eleven male collegiate cyclists (21.8 +/- 0.8 yr, 71.4 +/- 2.2 kg, and 8.6 +/- 0.9 % body fat) participated in a 6 week cycle training program that consisted of 5 days of high intensity interval and endurance training per week. Hematocrit (Hct), hemoglobin (Hb), red blood cell (RBC) count, serum iron, serum ferritin, and total iron binding capacity (TIBC) were analyzed from venous blood samples taken at baseline (B), and each week following interval training (T1-T6) and recovery (R1-R2). Dietary intakes including iron were monitored weekly. The dependent variables were analyzed by repeated measures ANOVA (p < 0.05). RBC count, Hb and Hct were significantly decreased compared to baseline at T3. Serum iron did not change significantly. Serum ferritin decreased significantly from 55.9 +/- 9.7 at B to 42.2 +/- 8.0 ng x ml -1 at T5 and remained depressed at T6, R1 and R2. TIBC was significantly increased above baseline at T3, T4, T6, R1 and R2. These results suggest that 6 weeks of high-intensity interval training can reduce iron stores. It is possible that this reduction in iron stores over time could adversely affect aerobic cycling performance.

Knee extensor torque and perceived discomfort during symmetrical biphasic electromyostimulation.

The purpose of this study was to examine the effects of simultaneously delivering 2 channels of electromyostimulation (EMS) current using 2 different electrode arrangements. Ten men and 10 women university students had 4 reusable electrodes placed (2 proximal, 2 distal) medial and lateral on the quadriceps muscle group. Isokinetic voluntary peak torque (VPT) of the quadriceps was determined at 60 degrees x s(-1). A symmetrical biphasic square wave current was applied using 2 independent channels in either a parallel (P) or a crossed (X) electrode arrangement. Subjects increased the current until maximal tolerance was achieved. No significant differences in percent VPT or perceived discomfort (PD) were observed between men and women. Percent VPT was significantly greater using the X (57.2 +/- 11.3%) vs. the P (46.5 +/- 10.7%) pad placement; however, pad placement did not affect peak PD. Data from this study suggest that a 2-channel application of EMS using a crossed electrode arrangement provides greater knee extensor force without greater discomfort.

Modeling and direct sensitivity analysis of biogenic emissions impacts on regional ozone formation in the Mexico-U.S. border area.

A spatially and temporally resolved biogenic hydrocarbon and nitrogen oxides (NOx) emissions inventory has been developed for a region along the Mexico-U.S. border area. Average daily biogenic non-methane organic gases (NMOG) emissions for the 1700 x 1000 km2 domain were estimated at 23,800 metric tons/day (62% from Mexico and 38% from the United States), and biogenic NOx was estimated at 1230 metric tons/day (54% from Mexico and 46% from the United States) for the July 18-20, 1993, ozone episode. The biogenic NMOG represented 74% of the total NMOG emissions, and biogenic NOx was 14% of the total NOx. The CIT photochemical airshed model was used to assess how biogenic emissions impact air quality. Predicted ground-level ozone increased by 5-10 ppb in most rural areas, 10-20 ppb near urban centers, and 20-30 ppb immediately downwind of the urban centers compared to simulations in which only anthropogenic emissions were used. A sensitivity analysis of predicted ozone concentration to emissions was performed using the decoupled direct method for three dimensional air quality models (DDM-3D). The highest positive sensitivity of ground-level ozone concentration to biogenic volatile organic compound (VOC) emissions (i.e., increasing biogenic VOC emissions results in increasing ozone concentrations) was predicted to be in locations with high NOx levels, (i.e., the urban areas). One urban center--Houston--was predicted to have a slight negative sensitivity to biogenic NO emissions (i.e., increasing biogenic NO emissions results in decreasing local ozone concentrations). The highest sensitivities of ozone concentrations to on-road mobile source VOC emissions, all positive, were mainly in the urban areas. The highest sensitivities of ozone concentrations to on-road mobile source NOx emissions were predicted in both urban (either positive or negative sensitivities) and rural (positive sensitivities) locations.

Temporal and spatial distributions of ozone in Atlanta: regulatory and epidemiologic implications.

Relationships between ambient levels of selected air pollutants and pediatric asthma exacerbation in Atlanta were studied retrospectively. As a part of this study, temporal and spatial distributions of ambient ozone concentrations in the 20-county. Atlanta metropolitan area during the summers of 1993, 1994, and 1995 were assessed. A universal kriging procedure was used for spatial interpolation of aerometric monitoring station data. In this paper, the temporal and spatial distributions of ozone are described, and regulatory and epidemiologic implications are discussed. For the study period, the Atlanta ozone nonattainment area based on the 1-h, exceedance-based standard of 0.12 ppm is estimated to expand--from 56% of the Atlanta MSA by area and 71% by population to 88% by area and 96% by population--under the new 8-h, concentration-based standard of 0.08 ppm. Regarding asthma exacerbation, a 4% increase in pediatric asthma rate per 20-ppb increase in ambient ozone concentration was observed (p-value = 0.001), with ambient ozone level representing a general indicator of air quality due to its correlations with other pollutants. The use of spatial ozone estimates in the epidemiologic analysis demonstrates the need for control of demographic covariates in spatiotemporal assessments of associations of ambient air pollutant concentrations with health outcome.

Early suppression of viremia by ZDV does not alter the spread of feline immunodeficiency virus infection in cats.

Prophylactic zidovudine (ZDV) therapy in feline immunodeficiency virus (FIV) inoculated cats was evaluated for 12 months postinfection (pi) and 11 months post drug treatment. Plasma FIV antigenemia was prevented in six of six ZDV-treated and none of six untreated cats during the initial phase of infection. The present study is a continuation of that earlier work. CD4 lymphocyte numbers from ZDV-treated cats were higher than in the untreated cats. CD8 lymphocytes numbers were maintained within control limits in the ZDV-treated cats, while they declined in the untreated cats. Anti-FIV antibody titers were comparable between the ZDV-treated and the untreated cats. Histologically, lymphoid tissues for the untreated and ZDV-treated cats were unremarkable and similar to those of the uninfected control cats. Low-level FIV antigen was detected by enzyme-linked immunosorbent assay in thymus or lymph node homogenates from 3 of 11 cats tested. Polymerase chain reaction analysis showed FIV DNA in blood, lymph node, bone marrow, spleen, thymus, and brain from FIV-inoculated cats irrespective of ZDV treatment. Therefore, while prophylactic ZDV treatment prevented detectable plasma antigenemia and FIV-induced CD8 lymphocyte decline, it did not slow infection of tissues and blood cells of FIV-inoculated cats.

Effects of interval training and a taper on cycling performance and isokinetic leg strength.

The purpose of this study was to determine whether changes in isokinetic leg strength parallel changes in cycling performance during a six-week high-intensity aerobic interval training program and a subsequent two-week taper. Eleven male collegiate cyclists participated in one competitive cycling graded exercise test, four consecutive days of aerobic intervals (30 min @82.2 +/- 0.74% HRmax, 1:1 work:relief), and four continuous rides (1-2 hr @65-80% HRmax) weekly. Pedalling cadence during training was generally 70-80 rpm suggesting a knee joint velocity of approximately 210 degrees.sec-1. Cycling performance and peak isokinetic torque (TQpk) for knee flexors (HAM) and knee extensors (QUAD) @30, 120, 210, and 300 degrees.sec-1 were assessed before, every two weeks during, and each week for two weeks following six weeks of interval training. Performance increased significantly during training (15%) and increased further during the taper (8%). QUAD TQpk @30 and 120 degrees.sec-1 increased significantly during training and the taper. In contrast, QUAD TQpk @210 and 300 degrees.sec-1 and HAM TQpk for all velocities were not significantly elevated following training. Interestingly, QUAD TQpk @300 but not 210 degrees.sec-1 significantly increased during the taper. Data from this study demonstrates that high-intensity aerobic interval cycling can promote gains in QUAD strength which occur primarily at contraction velocities slower than those utilized during cycling training. Additionally, a two-week taper can produce significant improvements in cycling performance (8%) and QUAD strength (8-9%) at 30 and 120 degrees.sec-1, however, the time-courses for these improvements do not parallel one another.

Exercise performance of collegiate rodeo athletes.

In this study we examined the physical, hematologic, and exercise response of 20 male and 10 female athletes of the National Intercollegiate Rodeo Association, Central Rocky Mountain Region. Male subjects were grouped by roughstock, steer wrestling, and roping events. Female athletes were grouped separately. Maximal aerobic capacity, pulmonary ventilation, respiratory exchange ratio, energy expenditure, maximal heart rate, blood pressure, treadmill time, pre- and postexercise lactate, percent body fat, lean body mass, blood chemistry, serum lipids, and reaction/movement time were analyzed by event. No significant differences (P greater than 0.05) were found in any of these categories between male events. Mean resting blood chemistry parameters of rodeo athletes were within normal ranges. Steer wrestling athletes possessed greater body size and lean body mass than other groups. When analyzing body composition, blood pressure, and total cholesterol:high-density lipoprotein (HDL) cholesterol ratios, results indicate average to low risk for coronary heart disease. When compared to other intermittent-activity sport athletes, college rodeo athletes appear to have similar aerobic capacities, but possess lower lean body mass and greater percent body fat.

Involvement of tyrosyl-tRNA synthetase in splicing of group I introns in Neurospora crassa mitochondria: biochemical and immunochemical analyses of splicing activity.

We reported previously that mitochondrial tyrosyl-tRNA synthetase, which is encoded by the nuclear gene cyt-18 in Neurospora crassa, functions in splicing several group I introns in N. crassa mitochondria (R. A. Akins and A. M. Lambowitz, Cell 50:331-345, 1987). Two mutants in the cyt-18 gene (cyt-18-1 and cyt-18-2) are defective in both mitochondrial protein synthesis and splicing, and an activity that splices the mitochondrial large rRNA intron copurifies with a component of mitochondrial tyrosyl-tRNA synthetase. Here, we used antibodies against different trpE-cyt-18 fusion proteins to identify the cyt-18 gene product as a basic protein having an apparent molecular mass of 67 kilodaltons (kDa). Both the cyt-18-1 and cyt-18-2 mutants contain relatively high amounts of inactive cyt-18 protein detected immunochemically. Biochemical experiments show that the 67-kDa cyt-18 protein copurifies with splicing and synthetase activity through a number of different column chromatographic procedures. Some fractions having splicing activity contain only one or two prominent polypeptide bands, and the cyt-18 protein is among the few, if not only, major bands in common between the different fractions that have splicing activity. Phosphocellulose columns resolve three different forms or complexes of the cyt-18 protein that have splicing or synthetase activity or both. Gel filtration experiments show that splicing activity has a relatively small molecular mass (peak at 150 kDa with activity trailing to lower molecular masses) and could correspond simply to dimers or monomers, or both, of the cyt-18 protein. Finally, antibodies against different segments of the cyt-18 protein inhibit splicing of the large rRNA intron in vitro. Our results indicate that both splicing and tyrosyl-tRNA synthetase activity are associated with the same 67-kDa protein encoded by the cyt-18 gene. This protein is a key constituent of splicing activity; it functions directly in splicing, and few, if any, additional components are required for splicing the large rRNA intron.

Skeletal muscle RNA synthesis following endurance and sprint exercise.

Two groups of male Wistar endurance- and sprint-acclimatized rats were used to study the time course of uridine uptake into skeletal muscle RNA following acute exercise. Endurance and sprint animals were killed at 0, 2, 18, 24, and 48 hr following 1 hr of either endurance (30 m X min-1) or sprint running (90 m X min-1). Red vastus (RV) and white vastus (WV) muscle samples were incubated for 30 min in a medium containing 1 microCi 5-[14C]uridine. Uridine uptake was determined in the myofibrillar-nuclear, mitochondrial, microsomal, and soluble fractions of skeletal muscle via liquid scintillation counting. A significant decrease in whole muscle uridine uptake into RNA was observed in RV muscles following endurance exercise as well as in WV of sprint-exercised rats. Sprint-exercised RV had significantly greater uridine uptake into RNA in the homogenate and myofibrillar-nuclear fraction 2-18 hr post exercise. Increased mitochondrial uridine incorporation into RNA was observed in endurance- and sprint-exercised muscles between 18 and 48 hr post exercise. A very large increment in microsomal uridine uptake was observed in sprint-exercised WV at 24 hr. These data suggest that while whole muscle RNA synthesis may decline immediately following acute exercise overload, increases are observed in specific muscle fractions. These changes appear to coincide with protein-specific adaptations to sprint and endurance exercise.

Exercise-induced skeletal muscle growth. Hypertrophy or hyperplasia?

Postnatal skeletal muscle growth in humans is generally ascribed to enlargement of existing muscle fibres rather than to cellular proliferation. Some evidence of muscle fibre division or splitting was provided in the nineteenth century. This evidence has more recently been supported by fibres obtained from regenerating muscle, and from muscle which has undergone stress-induced growth. Numerous investigators have reported indirect evidence for exercise-induced hypertrophy and hyperplasia. These findings are largely founded on secondary observations of fibre size or number differences expressed relative to muscle cross-sectional area. Since these observations in humans are open to methodological criticism, researchers have developed 3 animal models to represent exercise-induced human muscle growth. These include compensatory hypertrophy, stretch-induced hypertrophy, and weight lifting in trained animals. The results and criticisms of the experiments which have used these models are discussed in this review. In studies of muscle cross-sectional area, errors are created by fibres terminating intrafascicularly. Longitudinal growth of such fibres result in an overestimation of fibre number, and with the use of penniform muscles where fibres do not run parallel to the longitudinal axis of the muscle, the error is compounded. It was concluded that hyperplasia is not yet substantiated, and that new fibres, if present, may be the result of the development of satellite cells. Further experiments are required before a definitive answer can be provided. It is suggested that rigidly controlled exercise studies using contralateral control, fusiform muscles with analysis of individually teased muscle fibres be performed.

Diazinon treatment effects on heart and skeletal muscle enzyme activities.

The effect of low levels of diazinon treatment on four marker enzymes in rat heart and skeletal muscle have been investigated. Adult male Wistar rats were treated twice a week with a dose of 0.5 ml X kg-1 X day-1 diazinon for 28 weeks. Diazinon treated rats gained significantly less weight than Sham-treated controls. Typical differences in Succinate dehydrogenase (SDH), Lactate dehydrogenase (LDH), Phosphofructo kinase (PFK) and Hexokinase (HK) activities were observed between heart and skeletal muscles. Diazinon feeding had no effect on heart, soleus, gastrocnemius and plantaris SDH, LDH and PFK enzyme activities after 28 weeks. HK activity was significantly increased in sham-control soleus and plantaris muscles after 28 weeks. Diazinon feeding inhibited HK activity in plantaris muscle after 28 weeks treatment. These results demonstrate that chronic low levels of diazinon have little effect on the glycolytic and oxidative activity in heart and skeletal muscle.

Characteristics of national, divisional, and club male alpine ski racers.

Forty-two Canadian male alpine ski racers of either club, divisional, or national team status were studied by group to evaluate the physiological parameters that distinguish these athletes. Measurements of physical characteristics, flexibility, muscular power and endurance, aerobic and anaerobic power, and isokinetic leg strength were made. Correlations of the test variables were performed to evaluate the test battery for validity. While there were few physiological differences between the national and divisional skiers, club skiers scored consistently lower (P less than 0.01) in maximum number of sit-ups, vertical jump, anaerobic endurance, muscular power, 2-mile run time, isokinetic leg strength at 30 degrees X s-1, and hamstring-to-quadriceps strength ratio. However, no significant differences between groups were observed in sum of the skinfolds, flexibility, and isokinetic strength at 180 degrees X s-1. There were also no differences in VO2max between club and national team skiers. Highly-significant correlations were found between selected test variables, which indicated that some of the physiological parameters shared common variance. It seems that many of these physiological tests do not discriminate between national and divisional skiers. Club skiers would, however, appear to benefit from training programs designed to develop leg strength, power, and anaerobic endurance.

Anaerobic performance in middle and long distance runners.

The purpose of this study was to investigate the relationships between blood lactic acid (LA) accumulation, maximum anaerobic power, glycolytic enzyme activity, and skeletal muscle fibre composition in endurance trained runners. Venous LA was measured in 15 male middle distance (MD) and long distance (LD) runners before and after a 30 second all out ergometer ride. Muscle biopsies of the lateral gastrocnemius muscle were obtained prior to exercise for determination of lactate dehydrogenase (LDH), and phosphofructokinase (PFK) enzyme activities and histochemical classification of fast twitch (FT) and slow twitch (ST) muscle fibres. Significant differences were observed in %FT fibre composition (47.8(MD) and 34.6 (LD), and mean VO2 max values were significantly higher in the LD runners (62.8 (MD) and 68.7 (LD) ml.kg.-1 min.-1). Blood lactate values following maximal treadmill running were significantly higher in the MD group (15.0 mM) when compared with LD runners (11.9 mM). Total anaerobic power output was calculated according to the "Wingate Anaerobic Test" at 51 (MD) and 49 (LD) kpm. kg.-1 min.-1 and mean post-exercise LA values were 8.6 mM (MD) and 8.0 mM (LD). Similar non-significant differences were observed when muscular power was determined via the "Margaria Test" (109.6 (LD) kgm.sec-1). Correlations were determined and the best relationship was between PFK and %FT (R = 0.84). The data suggest that the ergometer test was of insufficient duration, and thus did not result in maximal accumulation of LA and/or metabolically produced LA is removed rapidly in endurance trained muscle. Endurance training in middle and long distance runners fails to produce high value for anaerobic power tests.

Uptake of 3H-leucine into different fractions of rat skeletal muscle following acute endurance and sprint exercise.

In order to study the specificity of the protein synthetic response to different acute exercise loads, 48 male rats served as non-exercised controls or ran at either 0.5 m . s-1 for 1 h or 1.5 m . s-1, 10 s: 20 s work : rest, for 1 h. Animals were killed and red and white vastus muscles excised from the controls or at 0, 2, 18, 24, or 48 h post-exercise. Muscle slices were incubated in a medium containing 10 muCi L-[4,5-3H]leucine for 30 min. Incorporation of the radionuclide was measured by liquid scintillation (dpm . mg-1 protein) in the whole homogenate and in four subcellular fractions. The endurance exercise elicited increased uptakes into the mitochondrial fractions of both red and white vastus at 2 and 18 h respectively. However, the mitochondrial uptake was depressed at 24 h in the red and at 2 h in the white vastus. Only in red vastus was incorporation into the soluble protein elevated following endurance exercise. The sprint protocol elicited increased uptake into soluble protein at 2 and 18 h in both red and white vastus and into mitochondrial protein at 18 and 24 h in the white vastus. The shifts in uptake in white vastus occurred in conjunction with depressed uptakes in the total homogenate. These data indicate that both the changes in the type of protein and the time course of amino acid incorporation following acute exercise are related to both the metabolic characteristics of the muscle fibers and the intensity of the exercise.