Physiological, metabolic, and performance implications of a prolonged hill walk: influence of energy intake.

Full Abstract

We aimed to examine the effects of different energy intakes on a range of responses that are relevant to the safety of hill walkers. In a balanced design, 16 men completed a strenuous self-paced mountainous hill walk over 21 km, under either a low-energy (2.6 MJ; 616 kcal) intake (LEI) or high-energy (12.7 MJ; 3,019 kcal) intake (HEI) condition. During the hill walk, rectal temperatures were measured continuously, and blood samples for the analysis of metabolites and hormones were drawn before breakfast and immediately after the walk. Subjects also completed a battery of performance tests that included muscular strength, reaction times, flexibility, balance, and kinesthetic differentiation tests. During the LEI, mean blood glucose concentrations leveled off at the low-middle range of normoglycemia, whereas, on the HEI, they were significantly elevated compared with the LEI. The maintained blood glucose concentrations, during the LEI, were probably mediated via the marked fat mobilization, reflected by a two- to fivefold increase in nonesterified fatty acids, 3-hydroxybutyrate, and glycerol concentrations. The LEI group showed significantly slower one- and two-finger reaction time, had an impaired ability to balance, and were compromised in their ability to maintain body temperature, when compared with the HEI group. The modestly impaired performance (particularly with respect to balance) and thermoregulation during the LEI condition may increase susceptibility to both fatigue and injury during the pursuit of recreational activity outdoors.

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Author information

Author/s: Ainslie, Philip N (PN); Campbell, Iain T (IT); Frayn, Keith N (KN); Humphreys, Sandy M (SM); MacLaren, Donald P M (DP); Reilly, Thomas (T);

Affiliation: Department of Physiology and Biophysics, Faculty of Medicine, University of Calgary, Calgary, Alberta, Canada T2N 4N1. painslie(-atsign-)ualgary.ca

Journal and publication information

Publication Type: Clinical Trial; Journal Article; Research Support, Non-U.S. Gov't

Journal: Journal of applied physiology (Bethesda, Md. : 1985) (J Appl Physiol), published in United States. (Language: eng)

Reference: 2003-Mar; vol 94 (issue 3) : pp 1075-83

Dates: Created 2003/02/06; Completed 2003/09/03; Revised 2008/11/21;

PMID: 12571136, status: MEDLINE (last retrieval date: 12/26/2008)

Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.

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MeSH headings (categories)

This article was linked to the MESH Headings shown below.

Adult
Blood Glucose - metabolism
Body Temperature - physiology
Diet
Energy Metabolism - physiology
Environment
Hand Strength
Heart Rate - physiology
Human Growth Hormone - blood
Humans

Hydrocortisone - blood
Insulin - blood
Lipid Metabolism
Male
Physical Endurance - physiology
Postural Balance - physiology
Psychomotor Performance - physiology
Reaction Time - physiology
Walking - physiology
Weather

Associated Chemicals: Blood Glucose (0) ; Insulin (11061-68-0) ; Human Growth Hormone (12629-01-5) ; Hydrocortisone (50-23-7)

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