The purpose of this study was to test the hypothesis that consuming a soft drink (i.e., a high-fructose, caffeinated beverage) during and following exercise in the heat elevates biomarkers of acute kidney injury (AKI) in humans. Twelve healthy adults drank 2 liters of an assigned beverage during 4 h of exercise in the heat [35.1 (0.1)°C, 61 (5)% relative humidity] in counterbalanced soft drink and water trials, and ≥1 liter of the same beverage after leaving the laboratory. Stage 1 AKI (i.e., increased serum creatinine ≥0.30 mg/dl) was detected at postexercise in 75% of participants in the Soft Drink trial compared with 8% in Water trial ( P = 0.02). Furthermore, urinary neutrophil gelatinase-associated lipocalin (NGAL), a biomarker of AKI, was higher during an overnight collection period after the Soft Drink trial compared with Water in both absolute concentration [6 (4) ng/dl vs. 5 (4) ng/dl, P < 0.04] and after correcting for urine flow rate [6 (7) (ng/dl)/(ml/min) vs. 4 (4) (ng/dl)/(ml/min), P = 0.03]. Changes in serum uric acid from preexercise were greater in the Soft Drink trial than the Water trial at postexercise ( P < 0.01) and 24 h ( P = 0.05). There were greater increases from preexercise in serum copeptin, a stable marker of vasopressin, at postexercise in the Soft Drink trial ( P < 0.02) than the Water trial. These findings indicate that consuming a soft drink during and following exercise in the heat induces AKI, likely via vasopressin-mediated mechanisms.
We tested the hypothesis that concussed college athletes (CA) have attenuated parasympathetic and sympathetic responses to face cooling (FC). Eleven symptomatic CA (age: 20 ± 2 years, 5 women) who were within 10 days of concussion diagnosis and 10 healthy controls (HC; age: 24 ± 4 years, 5 women) participated. During FC, a plastic bag filled with ice water (~0°C) was placed on the forehead, eyes, and cheeks for 3 min. Heart rate (ECG) and blood pressure (photoplethysmography) were averaged at baseline and every 60 sec during FC. High‐frequency (HF) power was obtained from spectral analysis of the R‐R interval. Data are presented as a change from baseline. Baseline heart rate (HC: 61 ± 12, CA: 57 ± 12 bpm; P = 0.69), mean arterial pressure (MAP) (HC: 94 ± 10, CA: 96 ± 13 mmHg; P = 0.74), and HF (HC: 2294 ± 2314, CA: 2459 ± 2058 msec2; P = 0.86) were not different between groups. Heart rate in HC decreased at 2 min (−7 ± 11 bpm; P = 0.02) but did not change in CA (P > 0.43). MAP increased at 1 min (HC: 12 ± 6, CA: 6 ± 6 mmHg), 2 min (HC: 21 ± 7, CA: 11 ± 7 mmHg), and 3 min (HC: 20 ± 6, CA: 13 ± 7 mmHg) in both groups (P < 0.01 for all) but the increase was greater at each interval in HC (P < 0.02). HF increased at 1 min (12354 ± 11489 msec2; P < 0.01) and 2 min (5832 ± 8002 msec2; P = 0.02) in HC but did not change in CA (P > 0.58). The increase in HF at 1 min was greater in HC versus CA (P < 0.01). These data indicate that symptomatic concussed patients have impaired cardiac parasympathetic and sympathetic activation.
Wiessner's analysis of stylistic variation in San arrows entails valuable ethnoarchaeological observation and insight. But her evidence contradicts the iconological theory she imposes upon it, whereby San artisans are thought to purposefully invest their products with ethnic symbolism in order to transmit social information to various target populations. However, an alternative view, according to which the arrows simply exhibit the ethnic style latent in all isochrestic behavior (see Sackett 1982), is consistent both with their formal variation and with the commonplace ethnic symbolism that the San themselves are reported to read into them. This view also provides a more reasonable explanation than does the iconological theory of why stylistic distinctions fail to emerge among San bands engaged in risk-sharing strategies. In any event, isochrestism is the basic source of ethnic style in material culture. Iconicism is a special case and ought not be invoked unless specific expectations are met by the evidence.
F utilize thermal behavior during exercise to a greater extent than M. During recovery, thermal behavior may compensate for elevated core temperatures in F despite mean body temperatures returning to pre-exercise levels.
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