Tennis, incidence of URTI and salivary IgA

Tennis played at an elite level requires intensive training characterized by repeated bouts of brief intermittent high intensity exercise over relatively long periods of time (1 - 3 h or more). Competition can place additional stress on players. The purpose of this study was to investigate the temporal association between specific components of tennis training and competition, the incidence of upper respiratory tract infections (URT1), and salivary IgA, in a cohort of seventeen elite female tennis players. Timed, whole unstimulated saliva samples were collected before and after selected 1-h training sessions at 2 weekly intervals, over 12 weeks. Salivary IgA concentration was measured by ELISA and IgA secretion rate calculated (mug IgA x ml(-1) x ml saliva x min(-1)). Players reported URTI symptoms and recorded training and competition in daily logs. Data analysis showed that higher incidence of URTI was significantly associated with increased training duration and load, and competition level, on a weekly basis. Salivary IgA secretion rate (S-IgA) dropped significantly after 1 hour of tennis play. Over the 12-week period, pre-exercise salivary IgA concentration and secretion rate were directly associated with the amount of training undertaken during the previous day and week (p < 0.05). However, the decline in S-IgA after 1 h of intense tennis play was also positively related to the duration and load of training undertaken during the previous day and week (p < 0.05). Although exercise-induced suppression of salivary IgA may be a risk factor, it could not accurately predict the occurrence of URTI in this cohort of athletes.

Cortisol, DHEA, performance and training in elite swimmers

Salivary cortisol (C) and DHEA concentrations were measured in 9 elite swimmers (4 female and 5 male) over a 37-week period, 5 to 12 times per swimmer, before 68 competitions. For female and male swimmers, no significant relationship was found between C, DHEA and performance. For the whole group, C was negatively correlated with week number of training (r = -0.31, p < 0.01). The incorporation of the cumulated distance swum as a second variable in the regression increased r to 0.56 (p < 0.01). The higher the cumulated distance swum, the higher C. No significant relationship was found between DHEA and distance swum. For individual swimmers, 3 of 4 females showed a significant negative relationship between C and cumulated dry-land training. No equivalent relationship was found for DHEA. The 2 males practicing dry-land training showed a significant and negative relationship between DHEA and cumulated dry-land training. No equivalent relationship was found for C. Thus, C and DHEA were not good predictors of swimming performance. C for individual females, and DHEA for individual males were considered useful markers for dry-land training stress.

Continuous glucose monitoring in diabetic long distance runners

Marathon running is growing in popularity, and many diabetic patients are participating in various marathon races all over the world each year. This study aimed to investigate the prevalence and extent of glycemic excursions (hypo- and hyperglycemic) during a marathon run in patients with well-controlled diabetes mellitus using a continuous glucose monitoring system (CGMS). Five subjects with type 1 and one patient with type 2 diabetes mellitus were monitored with the Medtronic MiniMed CGMS during the 2002 Vienna City Marathon (n = 3) or the Fernwarme run (n = 3) long distance runs of 42.19/15.8 km. All six patients finished their course. The CGSM system was well tolerated in all patients over an average duration of 34 +/- 4.0 hours and it did not limit the patients' activities. The mean running time for the Vienna city marathon was 257 +/- 8 min (247 to 274 min) and for the Fernwarme run 134 +/- 118 min (113 to 150 min). A total of 1470 blood glucose measurements (mean 245 readings per subject) were performed. During and after the marathons frequent hypo and hyperglycemic episodes with and without clinical symptoms were measured. Our data confirm that the CGMS may help to identify asymptomatic hypoglycemia or hyperglycemia during and after a long distance run. The system may also be helpful to improve our understanding about the individual changes of glucose during and after a marathon and may protect hypoglycemic or hyperglycemic periods in future races.

Highly demanding resistive vibration exercise program is tolerated during 56 days of strict bed-rest

Several studies have tried to find countermeasures against musculoskeletal de-conditioning during bed-rest, but none of them yielded decisive results. We hypothesised that resistive vibration exercise (RVE) might be a suitable training modality. We have therefore carried out a bed-rest study to evaluate its feasibility and efficacy during 56 days of bed-rest. Twenty healthy male volunteers aged 24 to 43 years were recruited and, after medical check-ups, randomised to a non-exercising control (Ctrl) group or a group that performed RVE 11 times per week. Strict bed-rest was controlled by video surveillance. The diet was controlled. RVE was performed in supine position, with a static force component of about twice the body weight and a smaller dynamic force component. RVE comprised four different units (squats, heel raises, toe raises, kicks), each of which lasted 60 - 100 seconds. Pre and post exercise levels of lactate were measured once weekly. Body weight was measured daily on a bed scale. Pain questionnaires were obtained in regular intervals during and after the bed-rest. Vibration frequency was set to 19 Hz at the beginning and progressed to 25.9 Hz (SD 1.9) at the end of the study, suggesting that the dynamic force component increased by 90%. The maximum sustainable exercise time for squat exercise increased from 86 s (SD 21) on day 11 of the BR to 176 s (SD 73) on day 53 (p = 0.006). On the same days, post-exercise lactate levels increased from 6.9 mmol/l (SD2.3) to 9.2 mmol/l (SD 3.5, p = 0.01). On average, body weight was unchanged in both groups during bed-rest, but single individuals in both groups depicted significant weight changes ranging from -10% to + d10% (p < 0.001). Lower limb pain was more frequent during bed-rest in the RVE subjects than in Ctrl (p = 0.035). During early recovery, subjects of both groups suffered from muscle pain to a comparable extent, but foot pain was more common in Ctrl than in RVE (p = 0.013 for plantar pain, p = 0.074 for dorsal foot pain). Our results indicate that RVE is feasible twice daily during bed-rest in young healthy males, provided that one afternoon and one entire day per week are free. Exercise progression, mainly by progression of vibration frequency, yielded increases in maximum sustainable exercise time and blood lactate. In conclusion, RVE as performed in this study, appears to be safe.

Muscle metabolism during constant- and alternating-intensity exercise around critical power

Few studies have focused on the metabolic responses to alternating high- and low-intensity exercise and, specifically, compared these responses to those seen during constant-load exercise performed at the same average power output. This study compared muscle metabolic responses between two patterns of exercise during which the intensity was either constant and just below critical power (CP) or that oscillated above and below CP. Six trained males (mean +/- SD age 23.6 +/- 2.6 y) completed two 30-minute bouts of cycling (alternating and constant) at an average intensity equal to 90% of CR The intensity during alternating exercise varied between 158% CP and 73% CP. Biopsy samples from the vastus lateralis muscle were taken before (PRE), at the midpoint and end (POST) of exercise and analysed for glycogen, lactate, PCr and pH. Although these metabolic variables in muscle changed significantly during both patterns of exercise, there were no significant differences (p > 0.05) between constant and alternating exercise for glycogen (PRE: 418.8 +/- 85 vs. 444.3 +/- 70; POST: 220.5 +/- 59 vs. 259.5 +/- 126mmol.kg(-1) dw), lactate (PRE: 8.5 +/- 7.7 vs. 8.5 +/- 8.3; POST: 49.9 +/- 19.0 vs. 42.6 +/- 26.6 mmol.kg(-1)dw), phosphocreatine (PRE: 77.9 +/- 11.6 vs. 75.7 +/- 16.9; POST: 65.8 +/- 12.1 vs. 61.2 +/- 12.7mmol.kg(-1)dw) or pH (PRE: 6.99 +/- 0.12 vs. 6.99 +/- 0.08; POST: 6.86 +/- 0.13 vs. 6.85 +/- 0.06), respectively. There were also no significant differences in blood lactate responses to the two patterns of exercise. These data suggest that, when the average power output is similar, large variations in exercise intensity exert no significant effect on muscle metabolism.