Cognitive effects of one season of head impacts in a cohort of collegiate contact sport athletes.

OBJECTIVE: To determine whether exposure to repetitive head impacts over a single season negatively affects cognitive performance in collegiate contact sport athletes. METHODS: This is a prospective cohort study at 3 Division I National Collegiate Athletic Association athletic programs. Participants were 214 Division I college varsity football and ice hockey players who wore instrumented helmets that recorded the acceleration-time history of the head following impact, and 45 noncontact sport athletes. All athletes were assessed prior to and shortly after the season with a cognitive screening battery (ImPACT) and a subgroup of athletes also were assessed with 7 measures from a neuropsychological test battery. RESULTS: Few cognitive differences were found between the athlete groups at the preseason or postseason assessments. However, a higher percentage of the contact sport athletes performed more poorly than predicted postseason on a measure of new learning (California Verbal Learning Test) compared to the noncontact athletes (24% vs 3.6%; p < 0.006). On 2 postseason cognitive measures (ImPACT Reaction Time and Trails 4/B), poorer performance was significantly associated with higher scores on several head impact exposure metrics. CONCLUSION: Repetitive head impacts over the course of a single season may negatively impact learning in some collegiate athletes. Further work is needed to assess whether such effects are short term or persistent.

Sensory level electrical muscle stimulation: effect on markers of muscle injury.

BACKGROUND: Monophasic high voltage stimulation (MHVS) is widely prescribed for the treatment of inflammation associated with muscle injury. However, limited scientific evidence exists to support its purported benefits in humans. OBJECTIVE: To examine the efficacy of early initiation of MHVS treatment after muscle injury. METHODS: In a randomised, cross over design, 14 men performed repetitive eccentric contractions of the elbow flexor muscles followed by either MHVS or control treatment. MHVS treatments were applied five minutes and 3, 6, 24, 48, 72, 96, and 120 hours after eccentric contractions. RESULTS: MHVS resulted in a significant reduction (p<0.05) in delayed onset muscle soreness 24 hours after eccentric exercise compared with controls. Elbow extension was significantly increased immediately after administration of MHVS compared with controls. No significant differences were observed between MHVS treatment and controls for maximal isometric strength, flexed arm angle, or arm volume. CONCLUSIONS: Early and frequent application of MHVS may provide transient relief from delayed onset muscle soreness and short term improvements in range of motion after injurious exercise. However, MHVS treatment may not enhance recovery after muscle injury because of lack of improvements in strength and active range of motion.

Nurses' perceptions of complementary and alternative medical therapies.

The purpose of this study was to identify the perceptions of nurses toward the effectiveness and safety, as well as their recommendations for and personal use of complementary and alternative medical therapies. A, random sample of 1000 nurses throughout the United States were surveyed using a three-wave mailing. About half of the respondents perceived there was conclusive evidence or preponderance of evidence that five therapies were effective: biofeedback, chiropractic, meditation/relaxation, multi-vitamins, and massage therapy. The same amount of nurses also perceived five therapies as definitely safe: hypnotherapy, chiropractic, acupressure, acupuncture, and healing touch. However, the nurses were most likely to recommend (regularly or periodically) four therapies: multivitamins, massage, meditation/relaxation, and pastoral/spiritual counseling. The vast majority (79%) of nurses perceived their professional preparation in this area to be fair or poor.

Weight-bearing exercise and markers of bone turnover in female athletes.

Weight-bearing activity provides an osteogenic stimulus, while effects of swimming on bone are unclear. We evaluated bone mineral density (BMD) and markers of bone turnover in female athletes (n = 41, age 20.7 yr) comparing three impact groups, high impact (High, basketball and volleyball, n = 14), medium impact (Med, soccer and track, n = 13), and nonimpact (Non, swimming, n = 7), with sedentary age-matched controls (Con, n = 7). BMD was assessed by dual-energy X-ray absorptiometry at the lumbar spine, femoral neck (FN), Ward's triangle, and trochanter (TR); bone resorption estimated from urinary cross-linked N-telopeptides (NTx); and bone formation determined from serum osteocalcin. Adjusted BMD (g/cm; covariates: body mass index, weight, and calcium and calorie intake) was greater at the FN and TR in the High group (1.27 +/- 0.03 and 1.05 +/- 0.03) than in the Non (1.05 +/- 0.04 and 0.86 +/- 0.04) and Con (1.03 +/- 0.05 and 0.85 +/- 0.05) groups and greater at the TR in the Med group (1.01 +/- 0.03) than in the Non (0.86 +/- 0.04) and Con (0.85 +/- 0.05) groups. Total body BMD was higher in the High group (4.9 +/- 0.12) than in the Med (4.5 +/- 0.12), Non (4.2 +/- 0.14), and Con (4.1 +/- 0.17) groups and greater in the Med group than in the Non and Con groups. Bone formation was lower in the Non group (19.8 +/- 2.6) than in the High (30.6 +/- 3.0) and Med (32.9 +/- 1.9, P < or = 0.05) groups. No differences in a marker of bone resorption (NTx) were noted. This indicates that women who participate in impact sports such as volleyball and basketball had higher BMDs and bone formation values than female swimmers.

Effects of intensified training and detraining on testicular function.

OBJECTIVE: To examine the effects of an increased training load and period of detraining on testicular function in male distance runners. DESIGN: Multiple-group time-series design using a control group. SETTING: University of Toledo and Toledo Hospital. PARTICIPANTS: Eight male runners and eight age-matched sedentary control subjects. Subjects were considered fit for participation after a physical and genital examination conducted by a physician. INTERVENTION: Subjects provided blood and semen samples every 2 weeks for 8 weeks. The training regimen for the runners consisted of 2 weeks at normal training (NT), 2 weeks at 143% of NT (IT1), 2 weeks at 186% of NT (IT2), and 2 weeks at 50% of NT (RT). These percentages represent increases in training distance (volume). MAIN OUTCOME MEASURES: Within the context of this investigation, the following hypothesis was developed: increases or decreases in training would not significantly alter sperm count, density, motility, or morphology, or concentrations of reproductive hormones or cortisol in runners. RESULTS: There were no statistically significant differences observed between runners and control subjects for any of the reproductive hormones or cortisol. In addition, there was no significant treatment effect for sperm count, motility, or morphology. The sperm levels in two runners in this investigation dropped to oligospermatic levels after IT2; however, total sperm count increased in both runners after 2 weeks of RT. CONCLUSION: Four weeks of increased training and 2 weeks of reduced training did not significantly affect the subjects in this investigation. It is possible that a particular level or degree of training must be surpassed before any clinical alterations are evident. Future longitudinal studies are necessary to identify the extent to which endurance training may alter reproductive hormones and testicular function.

Effects of resistance training on selected indexes of immune function in elderly women.

Women aged 67-84 yr were randomly assigned to either resistance exercise (RE, n = 15) or control group (C, n = 14). RE group completed 10 wk of resistance training, whereas C group maintained normal activity. Blood samples were obtained from the RE group (at the same time points as for resting C) at rest, immediately after resistance exercise, and 2 h after exercise before (week 0) and after (week 10) training. Mononuclear cell (CD3+, CD3+CD4+, CD3+CD8+, CD19+, and CD3-CD16+CD56+) number, lymphocyte proliferative (LP) response to mitogen, natural cell-mediated cytotoxicity (NCMC), and serum cortisol levels were determined. Strength increased significantly in RE subjects (%change 8-repetition maximum = 148%). No significant group, exercise time, or training effects were found for CD3+, CD3+CD4+, or CD3+CD8+ cells, but there was a significant exercise time effect for CD3-CD16+CD56+ cells. LP response was not different between groups, across exercise time, or after training. NCMC was increased immediately after exercise for RE subjects at week 0 and for RE and C groups at week 10. The week 0 and week 10 NCMC values were above baseline for both RE and C groups 2 h after exercise. In conclusion, acute resistance exercise did not result in postexercise suppression of NCMC or LP, and 10 wk of resistance training did not influence resting immune measures in women aged 67-84 yr.

Cross training: indices of training stress and performance.

Twenty well-trained runners (VO2max 4.6+/-0.5 L x min[-1]) were age and ability matched and assigned to either a cross training (CT) or run only group (RT). All subjects maintained normal running distance and intensity for 6 wk and reported for three additional training sessions per week. These workouts were performed outdoors on a 400-m track or measured road course (RT) or on a bicycle ergometer (CT). The sessions were as follows: (work x rest(-1) ratio = 1): 5 x 5 min at >95% VO2max/peak (Monday), 50-60 min at 70% VO2max/peak (Wednesday), and 3 x 2.5 min at >105% VO2max/peak, plus 6 x 1.25 min at >115% VO2max/peak (Friday). Subjects were tested before (PRE), after 3 wk (MID), and after 6 wk (POST) of intensified training. Blood samples were obtained from RT, CT, and ten controls (CON) at each time point (0600 h). Runners also completed a 10-min submaximal run at the same absolute intensity (velocity to elicit 75% of initial V02max) during which heart rate, RPE, and VO2 were measured. Each runner then completed a simulated 5-km race (time trial) on a treadmill. Total testosterone (TT), free testosterone (FT), cortisol (C), and creatine kinase activity (CK) were determined. Running economy was similar between RT and CT; however, RPE decreased significantly at MID and POST compared with that at PRE (P < 0.05; time effect). There were no significant differences among groups for TT, FT, or CK, but C was significantly lower in CON than in RT and CT. Performance was significantly faster (P < 0.05; time effect) in the 5-km race at MID (1076.1+/-81.4 s) and POST (1068.6+/-83.9) compared with PRE (1096.6+/-79.5) but was not different between CT and RT. In conclusion, RT and CT responded similarly to 6 wk of increased training, and both groups improved 5-km performance to a similar extent.

Hormonal responses to excessive training: influence of cross training.

The purpose of this investigation was to examine the changes in blood hormone levels elicited by increases in training volume. After 30 d of recording their training volume and intensity (normal training, 57.5 +/- 10.9 km.wk-1), 11 well-trained distance runners completed two randomly assigned 10 day periods of increased training volume (200% normal training). Each increased training regimen was preceded by two weeks of reduced training (80% normal training). The increased training regimens consisted of either running only (RT) at 200% of normal training distance or running (100% normal training) and cycling (kcal = 100% normal training: CT). During each increased training regimen the subjects ran 10 consecutive afternoons at a distance equivalent to 100% of normal training (approximately 75% VO2max) and performed eight additional morning sessions (0500-0800 h). During RT the subjects performed their morning workouts on a treadmill and during CT the workouts were performed on a bicycle ergometer. Blood samples were obtained (0500-0700 h) after 15 min supine rest after normal training, and before (day 0), on day five (day 5) and following ten days (day 11) of RT and CT. Serum was analyzed for testosterone, free testosterone, cortisol, adrenocorticotropic hormone, luteinizing hormone, and dehydroepiandrosterone sulfate. Free testosterone was significantly (p < 0.05) reduced on day 5 and day 11 of RT and CT compared to day 0 and total testosterone was lower on day 5 than day 0. However, no significant treatment or interaction effects were observed for total testosterone or free testosterone. Dehydroepiandrosterone sulfate was also significantly lower across time, i.e., day 11 was lower than day 0 and day 5; however, cortisol, adrenocorticotropic hormone, and luteinizing hormone were not significantly altered during RT or CT. The endocrine responses to an increased training volume with cross training and mode specific training were similar.

Run training vs cross training: influence of increased training on running economy, foot impact shock and run performance.

The purpose of the study was to compare changes in running economy, foot impact shock, run performance, and resting heart rate and blood pressure elicited by increases in training volume via run training (RT) and cross training (CT). After 30 d of normal training (NT), male runners (N = 11) completed two 10 d periods of increased training each preceded by 14 d of reduced training (80% NT). Subjects ran 10 consecutive days in the afternoon (100% of NT) and performed 8 additional workouts in the morning (100% of NT). The morning sessions were performed on a cycle ergometer (CT) or a treadmill (RT). Running economy, foot impact shock and lactate were assessed during submaximal running (3.9 +/- 0.06 m.sec-1) at D0 and D11. Following the submaximal run, subjects completed a simulated 5 km race on a treadmill. VO2 during the running economy test was significantly higher at D11 of CT (52.5 +/- 1.5) compared to RT (51.1 +/- 1.4 ml.kg-1.min-1). RER, carbohydrate oxidation, and lactate were significantly lower; whereas, foot impact shock was significantly higher following both training modes. No significant changes in run performance, resting heart rate and blood pressure occurred during the study. In summary, 10 d of increased training resulted in a reduced running economy for CT, and a lower carbohydrate oxidation and an increase in foot impact shock for both training modes.

Run training versus cross-training: effect of increased training on circulating leukocyte subsets.

The purpose of this study was to determine the effects of increased training via cross-training (run + cycle) and run training on circulating leukocyte subsets. Male runners (N = 11) participated in two randomly assigned increased training (IT) periods after 30 d of normal training (NT). Each IT began after a 14 d period of reduced training (80% of NT) followed by 10 d of IT (200% of NT). During IT, the subjects ran in the afternoon for 10 d (100% NT) and performed 8 additional training sessions in the morning (100% NT) on a treadmill (ITRT) or a bicycle ergometer (ITCT). Blood samples were obtained before (D0), on day 5(D5) and after 10 d (D11) of ITRT and ITCT. A significant increase in the CD4+/CD8+ ratio occurred at D5 compared with D0 and D11. The CD4+/CD8+ ratio was significantly lower during ITRT compared with ITCT at D11. The number of circulating CD3+, CD4+, and CD8+ cells were significantly reduced at D11 compared with D0. In conclusion, 10 d of IT resulted in a significant reduction in the number of circulating T cells independent of the training mode and a reduction in the CD4+/CD8+ ratio for ITRT but not for ITCT.