Association of Serum Vitamin D Levels and Stress Fractures in Collegiate Athletes.

BACKGROUND: Low vitamin D levels along with high-intensity athletic training may put an athlete at increased risk for a stress fracture. PURPOSE: To assess whether supplementation with vitamin D is associated with a reduced risk of stress fractures in college athletes. We also assessed differences in vitamin D levels among athletes participating in outdoor versus indoor sports. STUDY DESIGN: Cohort study; Level of evidence, 2. METHODS: The study participants included 802 National Collegiate Athletic Association Division I intercollegiate athletes (497 men and 305 women) on a sports team for at least 1 semester from 2012 to 2018. All athletes who had a baseline vitamin D level in their medical record were included. Athletes with vitamin D levels <40 ng/mL were given vitamin D supplements. We assessed differences in the rate of stress fracture among those who maintained or improved vitamin D levels to ≥40 ng/mL and those who did not, as well as differences in average baseline vitamin D levels by sport type (indoor vs outdoor). RESULTS: The rate of stress fracture was 12% higher (95% CI, 6-19; P < .001) for those who remained low in vitamin D compared with those who were low at baseline but improved their vitamin D status to ≥40 ng/mL. The rate of stress fracture was also 12% higher (95% CI, 5-18; P < .001) for those who had low vitamin D levels compared with those who maintained normal levels. The mean baseline vitamin D values were significantly higher for men participating in outdoor sports versus indoor sports. For men, the mean vitamin D level was 5.7 ng/mL higher (95% CI, 0.9-10.5; P = .01) in outdoor athletes. For women, the mean vitamin D level was 3.7 ng/mL higher (95% CI, -0.58 to 8.03; P < .04) for outdoor versus indoor sports. CONCLUSION: Study results indicated that correcting low serum vitamin D levels reduces the risk of stress fracture. This study also presented evidence that athletes who participate in indoor sports may be at greater risk for vitamin D deficiency than those who compete in outdoor sports.

Phylogenetic and environmental context of a Tournaisian tetrapod fauna.

The end-Devonian to mid-Mississippian time interval has long been known for its depauperate palaeontological record, especially for tetrapods. This interval encapsulates the time of increasing terrestriality among tetrapods, but only two Tournaisian localities previously produced tetrapod fossils. Here we describe five new Tournaisian tetrapods (Perittodus apsconditus, Koilops herma, Ossirarus kierani, Diploradus austiumensis and Aytonerpeton microps) from two localities in their environmental context. A phylogenetic analysis retrieved three taxa as stem tetrapods, interspersed among Devonian and Carboniferous forms, and two as stem amphibians, suggesting a deep split among crown tetrapods. We also illustrate new tetrapod specimens from these and additional localities in the Scottish Borders region. The new taxa and specimens suggest that tetrapod diversification was well established by the Tournaisian. Sedimentary evidence indicates that the tetrapod fossils are usually associated with sandy siltstones overlying wetland palaeosols. Tetrapods were probably living on vegetated surfaces that were subsequently flooded. We show that atmospheric oxygen levels were stable across the Devonian/Carboniferous boundary, and did not inhibit the evolution of terrestriality. This wealth of tetrapods from Tournaisian localities highlights the potential for discoveries elsewhere.

Treatment options for the management of exercise-induced asthma and bronchoconstriction.

Treatment for exercise-induced bronchospasm and exercise-induced asthma includes both pharmacologic and nonpharmacologic options. Pharmacologic agents that have been proven to be effective for treating these conditions include short- and long-acting ß2-adrenoceptor agonists, mast cell-stabilizing agents, anticholinergics, leukotriene receptor antagonists, and inhaled corticosteroids (ICS). When selecting the most appropriate medication, factors to consider include the effectiveness of each, the duration of action, frequency of administration, potential side effects, and tolerance level. Long-acting ß2-adrenoceptor agonists should not be used without ICS. Nonpharmacologic treatments include physical conditioning, incorporating a warm-up before and a cool-down period after exercise, performing nasal breathing, avoiding cold weather or environmental allergens, using a face mask or other aid to warm and humidify inhaled air, and modifying dietary intake. The data to support nonpharmacologic treatments are limited; however, they are routinely recommended because of the low risk associated with their use. This article highlights the advantages and limitations of each treatment option.

The diagnosis of asthma and exercise-induced bronchospasm in division I athletes.

OBJECTIVE: To determine the accuracy of clinically diagnosed exercise-induced bronchospasm (EIB) and asthma among National Collegiate Athletic Association Division I student athletes. DESIGN: Cohort study. SETTING: Division I university athletic department and primary care sports medicine clinic/athletic training room. PATIENTS: All varsity athletes were eligible for the study. Seventy-five participants entered the study; 74 completed all the study protocols. INTERVENTIONS: Study participants underwent measurement of exhaled nitric oxide (eNO), followed by baseline spirometry. Eucapnic voluntary hyperventilation (EVH) was then performed, followed by spirometry every 3 minutes for a total of 21 minutes to measure change in forced expiratory volume in 1 second. MAIN OUTCOME MEASURES: Exhaled nitric oxide levels, baseline spirometry, and response of forced expiratory volume in 1 second to EVH. RESULTS: There were a total of 16 subjects with a positive EVH test. There were 16 (80%) individuals using a bronchodilator who had a negative EVH test versus 4 (20%) who had a positive test. Mean eNO values were different across subject groups defined by treatment status, although not statistically significant. The highest mean eNO value of 24.32 ppb was found in subjects only taking bronchodilators compared with the lowest mean value of 16.75 ppb in athletes who were not taking any medications. CONCLUSIONS: The results from this study provide further evidence to support the need for objective testing to correctly diagnose EIB. These data suggest that measuring eNO may help to distinguish truly isolated EIB from asthma in athletes, but a larger study is needed to confirm these initial observations.

Arthroscopic ankle arthrodesis.

Arthroscopic ankle arthrodesis provides the foot and ankle surgeon with an alternative to traditional open techniques. Advancements in arthroscopic techniques and instrumentation have made the procedure easier to perform. Advantages include faster rates of union, decreased complications, reduced postoperative pain, shorter hospital stays, minimal loss of length of the lower limb, and minimal clinical deformity or shapechanges to the ankle. This article reviews the literature on the subject and discusses the procedure's indications and contraindications, and surgical technique. It concludes that while total ankle replacement continues to grow in popularity, arthroscopic ankle arthrodesis is a viable alternative for management of the end-stage arthritic ankle.

Protein metabolism in skeletal muscle

Two different approaches towards the study of protein turnover in skeletal muscle were made. The first approach involved the injection of 75Se Selenomethionine into rats and the subsequent measurement of the whole body decay rate of the 75Se activity in a 4 pi liquid scintillation counter. By this means it was hoped that the whole body decay curve could be analysed into exponentials representative of 'fast' (visceral protein) and 'slow' (muscle protein) pools. This proved not to be feasible. The special difficulties resulting from the use of 75Se-labelled amino acids are discussed. As a second approach a search was made for a technique for labelling muscle proteins so that radioactivity decay rates could be used directly to calculate rates of synthesis and catabolism without the usual errors arising from isotope reutilisation. 75Se selenomethionine, 14C-6 arginine, 14C-Na2 CO3 and 14C-1 glutamate were investigated. 14C-Na2 CO3 proved to be suitable especially if the decay rates of separate and glutamate isolated from muscle proteins labelled with 14C Na2 CO3 are measured. The lack of reutilisation of label is discussed in terms of the metabolic activity of the carboxyl groups of these dicarboxylic amino acids. The effects of acute deprivation of calories and protein on synthesis and catabolism of muscle and liver protein was measured in rats, using the 14C-Na2 CO3 labelling method. The synthesis rates for muscle proteins, 0.25 and 0.097 days-1 for sarcoplasmic and myofibrillar proteins respectively are the fastest reported in the literature. The total protein synthesised and catabolised in muscle sarcoplasmic and myofibrillar fractions was calculated and compared with liver. The protein free diet caused a reduction in synthesis rates in liver and muscle protein with no change in the distribution pattern between the tissues. The starved rats showed a shift in the distribution pattern of synthesis towards liver and a concomitant shift towards muscle in catabolism. The results are discussed in terms of the mobility and therefore importance of muscle protein metabolism in the economy of the whole animal (AU)

Protein turnover in skeletal muscle. I. The measurement of rates of synthesis and catabolism of skeletal muscle protein using [14C]Na2CO3 to label proteins

The turnover of rat skeletal muscle protein was studied using [75Se]selenomethionine, [6-14C]arginine and [14C]Na2CO3 to label protein. In rats labelled with both [75Se]selonomethionine and [14C]Na2CO3 the 14C activity of mixed skeletal muscle protein fell rapidly with a half-life of 6.0 days for the specific activity and 10.5 days for the total activity. There was no loss of 75Se activity from muscle protein during the 12 days of the experiment. Following the injection of [6-14C]arginine both sarcoplasmic and myofibrillar proteins continued to incorporate label for 6 days after which time the label was lost fairly rapidly. Following injection of [14C]Na2CO3 muscle protein was maximally labelled by 6h, at which time specific activity of the free amino acids had fallen to a very low level. Aspartate and glutamate in particular had lost over 99 percent of their maximum activity by this time in comparison to arginine which was still highly labelled after 24h. 14C activity was lost more rapidly from aspartate and glutamate isolated from sarcoplasmic and myofibrillar protein than from other labelled amino acids. The half-lives of the two protein fractions were 3.9 and 7.2 days from the specific activity curves and 6.0 and 19.0 days from the total activity curves. The differences between the half lives of muscle proteins labelled with amino acids are discussed in terms of the effects of reutilization of the labelled amino acids used. It is postulated that aspartate and glutamate labelled by the injection [14C]CO3= are only reutilized to a very small extent and therefore afford the means by which the rates of protein synthesis and catabolism in skeletal muscle can be measured with reasonable accuracy (Summary)

Total body potassium, muscle electrolytes, and glycogen in malnourished children

Total body potassium, muscle potassium, magnesium, and glycogen have been estimated in infants while they were malnourished, during recovery, and in several after they were fully recovered. Muscle potassium was curvilinearly related to the total body potassium. Muscle magnesium was reduced, and the potassium/magnesium ratio was depressed in children with low muscle potassium values, implying differential loss of muscle potassium. Muscle potassium was linearly related to muscle glycogen. Twenty-four-hour urinary excretion of creatinine was measured; by assuming that 1 mg. of creatinine was derived from 20 Gm. of muscle, calculations of muscle mass were made. In children with a total body potassium over 40 mEq. per kilogram of body weight, muscle potassium contributed approximately one half of the total body potassium; this ratio decreased significantly when body potassium fell to very low values. (AU)

Protein turnover in skeletal muscle. I. The effect of starvation and a protein-free diet on the synthesis and catabolism of skeletal muscle proteins in comparison to liver

Rates of synthesis and catabolism of liver and muscle sarcoplasmic and myofibrillar protein have been measured in young control, starved and protein (deprived) rats using [14C]Na2CO3 to label protein. Half-lives for synthesis of 1.35, 2.8 and 7.2 days for liver, sarcoplasmic and myofibrillar proteins, respectively were obtained, whilst half-lives for catabolism were 1.55, 3.6 and 15.6 days in each case in the control animals. The protein free diet for 3 days caused a small decrease in the rate of synthesis of liver and muscle proteins. The catabolic rate of liver protein was increased by 20 percent whilst there was a smaller increase in the catabolic rate of myofibrillar proteins. Starvation for 3 days caused a 20 percent reduction in the rate of liver protein synthesis whilst there were greater reductions in muscle protein synthesis. The catabolic rate of liver protein was only slightly increased whereas there was a 75 percent increase in the rate of myofibrillar protein breakdown. The total amount of protein synthesis and catabolism in liver and the 2 muscle protein fractions over the first 3 days of the 3 regimes were calculated. Muscle protein turnover, in particular myofibrillar, was shown to be very sensitive to dietary protein and/or calorie deficiency. These results are discussed in terms of the mobility and therefore importance of muscle protein metabolism in the economy of the whole animal. (AU)

The turnover of [75 Se] selenomethionine in infants and rats measured in a whole body counter

The gamma-emitting amino acid [75Se]selenomethionine was given to rats and to human infants, and the rate and route of excertion of 75Se was followed for several weeks by daily measurements in a 4 pi whole body counter. These data were used to calculate the turnover rate of total body protein, and the results were checked against other, technically more difficult, methods.(AU)