Maurie J. Luetkemeier

Hypervolemia and cycling time trial performance

Ten experienced cyclists rode three simulated time trials to determine whether hypervolemia was associated with improvements in cycling time trial performance. The conditions were: exercise-induced hypervolemia (ExH), dextran-induced hypervolemia (DxH), and euvolemia (Eu). ExH was induced by 3 d of submaximal cycling lasting an average of 92.9 min at an average relative intensity of 68%. DxH was induced by acute plasma volume expansion with 400 +/- 121 ml of a 6% dextran solution. Compared with Eu, ExH and DxH were associated with 9.4% and 8.7% elevations in blood volume as well as 11.1% and 12.4% elevations in plasma volume, respectively. Performance was significantly improved (P < 0.05) (i.e., target work goal reached earlier) during ExH (81.41 +/- 5.52 min) and DxH(81.36 +/- 5.06 min) than during Eu (90.87 +/- 5.27 min). Average power was significantly higher during E x H (246 +/- 13 W) and DxH (245 +/- 14 W) than during Eu (221 +/- 15 W). There were no significant differences in performance time or average power between the two hypervolemic conditions. Average sweat rates were significantly elevated during ExH (22.6 +/- 1.4 ml.min-1) and DxH (22.2 +/- 1.6 ml.min-1) than during Eu (20.4 +/- 1.7 ml.min-1). Rectal temperatures rose from approximately 37.2-39.2 degrees C during each time trial but there were no significant differences in T(re) between trials. In conclusion, hypervolemia, whether induced by short-term training or dextran-infusion, had a beneficial effect on performance and average power during simulated time trials lasting approximately 90 min. These improvements in performance were related to hypervolemia rather than other short-term training adaptations.

Skin Tattoos Alter Sweat Rate and Na+ Concentration

The popularity of tattoos has increased tremendously in the last 10 yr particularly among athletes and military personnel. The tattooing process involves permanently depositing ink under the skin at a similar depth as eccrine sweat glands (3–5 mm). Purpose The purpose of this study was to compare the sweat rate and sweat Na+ concentration of tattooed versus nontattooed skin. Methods The participants were 10 healthy men (age = 21 ± 1 yr), all with a unilateral tattoo covering a circular area at least 5.2 cm2. Sweat was stimulated by iontophoresis using agar gel disks impregnated with 0.5% pilocarpine nitrate. The nontattooed skin was located contralateral to the position of the tattooed skin. The disks used to collect sweat were composed of Tygon® tubing wound into a spiral so that the sweat was pulled into the tubing by capillary action. The sweat rate was determined by weighing the disk before and after sweat collection. The sweat Na+ concentration was determined by flame photometry. Results The mean sweat rate from tattooed skin was significantly less than nontattooed skin (0.18 ± 0.15 vs 0.35 ± 0.25 mg·cm−2·min−1; P = 0.001). All 10 participants generated less sweat from tattooed skin than nontattooed skin and the effect size was −0.79. The mean sweat Na+ concentration from tattooed skin was significantly higher than nontattooed skin (69.1 ± 28.9 vs 42.6 ± 15.2 mmol·L−1; P = 0.02). Nine of 10 participants had higher sweat Na+ concentration from tattooed skin than nontattooed skin, and the effect size was 1.01. Conclusions Tattooed skin generated less sweat and a higher Na+ concentration than nontattooed skin when stimulated by pilocarpine iontophoresis.