Rudi A Meir

The effect of jersey type on thermoregulatory responses during exercise in a warm humid environment (Thesis)

Rudi A. Meir — Thu, 20 Aug 2009 17:07:39 PDT

The thermoregulatory responses of subjects wearing two different forms of rugby league jersey, one with plastic sponsorship recognition and numbering (trial Gl) and one without (trial G2), and a lightweight alternative (trial G3), were compared with a trial without any form of upper body garment (trial GO). Ten male volunteers, mean age 20.9 (�2.3) years, height 179.8 (�4.7) cm, weight 80.2 (�8.9) kg, and body surface area 1.99 (�0.13) m2, participated in this study. Subjects had a mean maximal oxygen uptake capacity of 56.0 (�6.3) ml.kg.min-1 and a sum of 8 skinfolds of 80.6 (�23.8) mm. Subjects were exercised at approximately 50% of maximal oxygen uptake in a warm humid environment for 50 minutes. Mean ambient temperature was 27.6�C (�0.32) with a relative humidity of 64.7% (�1.44). Measurements of core and skin (7 sites) temperature, heart rate, oxygen uptake, plasma volume, peak lactate concentration, and pre- and post-trial body weight, hematocrit and garment weight were recorded. The statistical results showed that all subjects experienced significant (p ≤.0001) decreases in body weight representing a percentage decrease ranging from 1.2-1.3%. No significant difference was found between trials with respect to body weight change. No significant effect of garment type was found on pre- and post-trial hematocrit, plasma volume changes or peak blood lactic acid concentration. However, mean peak lactate was highest for trial Gl (5.6 mmol.L-1 �2.2) and lowest for trial G3 (4.6 mmol.L-1 �1.27). Post-trial core temperature was significantly (p≤ .0001) higher than the resting value; no significant difference was found between trials. The mean absolute increase for all experimental trials was 0.9�C. A significant (p≤.005) difference between mean total (7 sites) skin temperature was found with a post-hoc test revealing that trials Gl and G2 were significantly higher than trial GO; no significant difference was found when comparing trial G3 with trial GO or when comparing the garments between each other. Mean skin temperature under the garment (4 sites) was found to be significantly (p≤.05) higher for all trials involving a garment when compared with mean skin temperature outside (3 sites) the garment; no significant difference was found between trials. Mean oxygen uptake was significantly different between trials (p≤.005), with trial Gl and G3 found to be significantly lower than trial GO; no difference was found when comparing the garments with each other. Post-trial garment weights were significantly (p≤.001) heavier than pre-trial and were significantly (p≤.0001) different when compared with each other. There was no significant effect on heart rate, haematocrit, plasma volume changes, peak blood lactic acid concentration, or core temperature due to garment type. However, differences in skin temperature suggest that the garment used in trial G3 may have a benefit. Further research should consider the impact of increased exercise intensity and/or environmental temperature and humidity on the measured parameters while wearing the garments described in this study.

Natural Killer cell numbers and natural killer cytotoxic activity after 6 weeks of testosterone enanthate administration in health young males

Sonya M. Marshall-Gradisnik — Mon, 03 Aug 2009 13:52:50 PDT

The effect of short-term use of testosterone enanthate on muscle strength and power in healthy young males

Shane Rogerson — Mon, 03 Aug 2009 13:52:48 PDT

Natural killer cell numbers and natural killer cytotoxic activity after six weeks of testosterone enanthate administration in healthy young males

Sonya M. Marshall-Gradisnik — Mon, 03 Aug 2009 13:52:46 PDT

Fan reaction to the match day experience: a case study in English professional rugby league football

Rudi A. Meir — Sun, 28 Jun 2009 10:32:27 PDT

Although product augmentation is nothing new in the traditional consumer services sector, it is still to be applied widely across the professional sport industry globally.

A preliminary investigation into the long-term injury consequences reported by retired baseball players

Rudi A. Meir — Sun, 07 Jun 2009 10:24:51 PDT

Seventy-five retired baseball players participated in a survey (37.8% response rate) in order to establish the long-term consequences of injuries sustained during their playing careers. Respondents had a mean age of 55.8 (�11.4) years with a mean age of 41.3 (�11.4) years at retirement from play. The mean overall rate of injury suffered per player/playing career was 5.6 (�7.1). 54.7% of respondents experienced a major injury (i.e. injury resulting in 5 or more consecutive weeks absence from training and play) with a mean major injury per player/playing career of 1.5 (�2.2). The rate for significant injuries (i.e. injury resulting in more than 1 week but less than 5 weeks absence from training and play) was 4.1 (�6.5) per player/playing career. Catchers had significantly less injuries than all other positions (p = 0.027). 18.7% of all respondents reported suffering from arthritis, 24% from restricted joint mobility and 4% from chronically stiff fingers; all of these conditions were associated with their participation in baseball based on medical examination by their GP or medical specialist. 29.3% of respondents indicated that they had incurred additional medical costs and 12% reported significant loss of income associated with their injuries. Some injuries were severe enough that they resulted in extended stays in hospital producing costs carried by the health care system.

Natural killer cell activity following six weeks of strength training in healthy young males with/without testosterone enanthate administration

Sonya M. Marshall-Gradisnik — Wed, 20 May 2009 17:12:16 PDT

There is limited information on the acute immune response to resistance-training programs in combination with short-term administration of the anabolic androgenic steroid, testosterone enanthate (TE), in healthy young males. Eighteen healthy young men were match-paired and randomly assigned in a double-blind manner to either a TE or a placebo (PG) group. All subjects performed a structured resistance-training program while receiving injection of either TE at the dosage of 3.5 mg per kilogram body mass, or saline as placebo, once weekly for 6 weeks. A 10-second all-out cycle sprint test was conducted at the beginning (Week 0) and end (Week 6) of the treatment period. NK, B and T lymphocyte populations were counted and natural killer cytotoxic activity (NKCA) was measured prior to and 5 minutes post the cycle sprint at Weeks 0 and 6. The TE group significantly increased their total work in the 10-second cycle sprint test from Week 0 to Week 6 (p< 0.04), while there was no significant increase for total work in the PG group. There was a significant increase in NKCA from Week 0 to Week 6 (p < 0.05) in the PG group. A significantly higher NKCA in the PG group than in the TE group was found in the post exercise sample in Week 6 (p < 0.04). No significant differences were found between groups for the lymphocyte subsets. The 6-week strength training increased acute NKCA response to anaerobic type of exercise as shown in the PG group. Although dosing of TE enhanced anaerobic performance, the NKCA response in the TE group was lower than that in the PG group. The impact of this altered immune response on athletes' health requires further investigation.

Pre- and post-game body mass changes during an international rugby tournament: a practical perspective

Rudi A. Meir — Wed, 29 Apr 2009 18:57:15 PDT

Pre- and post-game body mass changes were recorded throughout an international rugby union tournament to determine changes in body mass when training and competing on consecutive days. A squad of 28 players with a mean (�SD) age of 20.0 yrs (�0.6), height of 1.85 m (�0.1) and body mass of 94.71 kg (�10.71) were selected to play for England and to participate in an international championship in Sydney, Australia. From the squad, 22 players played in 1 or more of 4 games over a 10-day period from the day of the first match to the day of the last match. Data were collected for a total of 84 player appearances across the 4 games. Players had their body masses recorded prior to leaving England, upon arrival in Australia, and pre- and post-game during the tournament. Players were allowed to ingest fluid ad libitum throughout each match. The mean (�SD) ambient temperature and relative humidity across all games was 18.5�C (�1.63) and 39.5% (�17.7), respectively. Pre- and post-game comparisons of body masses for all player appearances were significantly different (p < 0.00), representing a mean loss of 0.94 kg (�0.94). However, there was no significant difference between games or player position (forwards vs. backs). The results demonstrate that if appropriate hydration practices are implemented, they may reduce the compound effect of fluid loss when playing multiple games in a short period of time. Strategies include daily monitoring of body mass and fluid intake and educating players about the importance of fluid intake to recovery and subsequent performance when playing and training on consecutive days.

"Managing" the coaching environment to enhance performance

Rudi A. Meir — Wed, 29 Apr 2009 18:57:13 PDT

The use of body mass changes as a practical measure of dehydration in team sports

Gemma Harvey — Wed, 29 Apr 2009 18:57:11 PDT

Body mass changes, hematocrit, specific gravity and urine colour were recorded during two games of soccer to determine which of these methods was the most practical in a field setting for monitoring dehydration. Members (n=13) of a premiership soccer team with a mean age of 22.6 (+/-4.9) years old, height of 177.8 (+/-7.1)cm and sum of skinfolds (four sites) of 37 (+/-12.8) were invited to participate in this study with 11 participating in each game. Players had weight, hematocrit, specific gravity and urine colour recorded pre- and post-game. Players were allowed to ingest fluid ad libitum throughout the matches with the amount consumed recorded. Urine excretion was also recorded and included in the calculation of final body mass loss (kg). A mean ambient temperature of 21 degrees C and relative humidity 77% was recorded for both games. Pre- and post-game body mass, sweat loss, hematocrit, urine specific gravity and colour were significantly different (p<0.01) for both games. Linear mixed effects models were fitted to the data in order to identify an optimal prediction equation for sweat loss. The model predicting from mass change was clearly the best fitting. The results demonstrate that a change in body mass during a game of soccer is an effective method of monitoring dehydration due to sweat loss when compared to other known methods that may be invasive and inappropriate in the field.