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  • Author: João C. Dias x
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João C. Dias, Melissa W. Roti, Amy C. Pumerantz, Greig Watson, Daniel A. Judelson, Douglas J. Casa and Lawrence E. Armstrong

Context:

Dieticians, physiologists, athletic trainers, and physicians have recommended refraining from caffeine intake when exercising because of possible fluid-electrolyte imbalances and dehydration.

Objective:

To assess how 16-hour rehydration is affected by caffeine ingestion.

Design:

Dose–response.

Setting:

Environmental chamber.

Participants:

59 college-age men.

Intervention:

Subjects consumed a chronic caffeine dose of 0 (placebo), 3, or 6 mg · kg−1 · day−1 and performed an exercise heat-tolerance test (EHT) consisting of 90 minutes of walking on a treadmill (5.6 km/h) in the heat (37.7 °C).

Outcome Measures:

Fluid-electrolyte measures.

Results:

There were no between-group differences immediately after and 16 hours after EHT in total plasma protein, hematocrit, urine osmolality, specific gravity, color, and volume. Body weights after EHT and the following day (16 hours) were not different between groups (P > .05).

Conclusion:

Hydration status 16 hours after EHT did not change with chronic caffeine ingestion.

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Fabianna R. de Jesus-Moraleida, Paulo H. Ferreira, Juscelio P. Silva, André G.P. Andrade, Rosangela C. Dias, João Marcos D. Dias, Marcella G. Assis and Leani S.M. Pereira

Low back pain (LBP) can be less disabling in those who are physically active. This study analyzed the association between physical activity (PA)- and LBP-related disability in older people with LBP, exploring if this association was mediated by depressive symptoms. The authors analyzed the relationship between PA levels and disability using the short version of the International Physical Activity Questionnaire and the Roland–Morris Disability Questionnaire, respectively, collected at baseline from the Brazilian Back Complaints in the Elders study. The authors investigated depressive symptoms as a mediator of this association using the Center of Epidemiologic Studies Depression scale. PA was inversely associated with disability. This association was smaller when considering the indirect effect through depressive symptoms. Thus, depressive symptoms partially mediated the association between PA and disability in older adults with LBP, and higher levels of PA were associated with less depressive symptoms and disability.

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Lawrence E. Armstrong, Amy C. Pumerantz, Melissa W. Roti, Daniel A. Judelson, Greig Watson, Joao C. Dias, Bülent Sökmen, Douglas J. Casa, Carl M. Maresh, Harris Lieberman and Mark Kellogg

This investigation determined if 3 levels of controlled caffeine consumption affected fluid-electrolyte balance and renal function differently. Healthy males (mean ± standard deviation; age, 21.6 ± 3.3 y) consumed 3 mg caffeine · kg−1 · d−1 on days 1 to 6 (equilibration phase). On days 7 to 11 (treatment phase), subjects consumed either 0 mg (C0; placebo; n = 20), 3 mg (C3; n = 20), or 6 mg (C6; n = 19) caffeine · kg−1 · d−1 in capsules, with no other dietary caffeine intake. The following variables were unaffected (P > 0.05) by different caffeine doses on days 1, 3, 6, 9, and 11 and were within normal clinical ranges: body mass, urineosmolality, urine specific gravity, urine color, 24-h urine volume, 24-h Na+ and K+ excretion, 24-h creatinine, blood urea nitrogen, serum Na+ and K+, serum osmolality, hematocrit, and total plasma protein. Therefore, C0, C3, and C6 exhibited no evidence of hypohydration. These findings question the widely accepted notion that caffeine consumption acts chronically as a diuretic.