Caffeine Effects on Physical and Cognitive Performance during Sustained Operations


  1. McLellan, T.M.
  2. Kamimori, G.H.
  3. Voss, D.M.
  4. Tate, C.
  5. Smith, S.J.R.
Corporate Authors
Defence R&D Canada - Toronto, Toronto ONT (CAN);Walter Reed Army Inst of Research, Silver Spring MD (US);New Zealand Defence Force, Auckland (New Zealand)
This study examined the effects of caffeine (CAF) on physical performance and vigilance during 4 days and 3 nights of sustained operations in Special Forces personnel. Twenty soldiers (28.6 „b 4.7y, 81.2 „b 8.0 kg) were divided equally into placebo (PLAC) and CAF groups. A 4 km run that included 3 obstacles (OBST) was completed each morning with the performance on Day 2 after an 8-hour sleep representing control (CON). From 0130 to 0615 of Days 3-5, soldiers performed two 2-hour vigilance (VIG) sessions in the field. PLAC or 200 mg of CAF was administered at 2145 of Day 2-4 and at 01:00, 03:45, and approximately 07:00 on Day 3-5. The run commenced within 30 minutes of receiving the final dose. Soldiers were provided with a 4-hour sleep period from 1330-1730 during Days 3 and 4. VIG during Days 3-5 was greater for CAF and not different from CON. Total run time was faster for CAF (29.7 ¡Ó 2.0 min) compared with PLAC (30.7 ¡Ó 2.9 min) on DAY 3 due to faster completion of OBST (8.7 ¡Ó 0.7 min vs 9.2 ¡Ó 1.0 min for CAFF and PLAC, respectively). Thereafter, run times decreased for both groups on Days 4 and 5 compared with CON due primarily to an increase in pace between OBST. It was concluded that CAF maintained both vigilance and physical performance for Special Forces personnel during sustained operations that require periods of overnight wakefulness and restricted opportunities for daytime sleep.

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continuous operations, physical and cognitive performance, ergogenic and cogniti
Report Number
DRDC-TORONTO-SL-2007-034 — Scientific Literature
Date of publication
01 Sep 2007
Number of Pages
Reprinted from
Aviation, Space and Environmental Medicine, vol 78, no 9, 2007, p 871-877
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