Evaluation of stress responses to interval training at low and moderate altitudes.
OBJECTIVE
The purpose of the present field study was to explore whether extensive interval training (IT) performed with a similar behavior of blood lactate (LA) at an altitude of 1800 m (ALT) and near sea level (SL) goes along with a comparable hormonal, metabolic, and acute phase response in highly trained endurance athletes.


METHODS
Twelve distance runners (VO2 64.6 +/- 6.9 mL.kg(-1) ) performed IT (10 x 1000 m, 2-min rest) at SL with a running velocity (V) corresponding to 112% of the individual anaerobic threshold (IAT). After an acclimatization period of 7 d, IT was repeated with a lower V (107% IAT) at ALT. Blood samples were drawn at rest, 0, 0.3, 3, and 24 h after IT. LA during IT was similar at SL and ALT (5.4 +/- 1.3/5.3 +/- 1.2 mmol.L(-1)), whereas HR tended to be higher at SL.


RESULTS
Postexercise rises in plasma noradrenaline (NA), NA sulfate, adrenaline, glucose, interleukin-6 (IL-6), and neutrophils were significantly more pronounced at ALT. The increase of cortisol and human growth hormone showed an insignificant trend toward higher values at ALT. A slight but significant increase of plasma erythropoietin was only apparent after IT at ALT. No differences between either condition were observed for exercise-related changes in free fatty acids, IL-8, lympho-, or monocyte counts.


CONCLUSIONS
In spite of a matched accumulation pattern of LA between ALT and N, stress responses, such as sympathetic activation and hepatic glucose release, still appear to be greater at ALT. This additional impact of moderate ALT on the stress response to IT should be taken into account if repeated training sessions are performed within a short period of time.
Niess
Andreas Michael
AM
Center of Internal Medicine, Department of Rehabilitative and Preventive Sports Medicine, University of Freiburg, Freiburg, Germany. niess@msml.ukl.uni-freiburg.de
Fehrenbach
Elvira
E
Strobel
Gunther
G
Roecker
Kai
K
Schneider
Elisabeth Marion
EM
Buergler
Julia
J
Fuss
Simone
S
Lehmann
Rainer
R
Northoff
Hinnak
H
Dickhuth
Hans-Hermann
HH
D000328:Adult; D000531:Altitude; D016207:Cytokines / Q000097:blood; D005260:Female; D005947:Glucose / Q000378:metabolism; D006801:Humans; D006854:Hydrocortisone / Q000097:blood*; D019344:Lactic Acid / Q000097:blood*; D008297:Male; D009638:Norepinephrine / Q000097:blood; D010807:Physical Endurance; D012420:Running / Q000502:physiology*; D013315:Stress, Psychological
D016207:Cytokines; D019344:Lactic Acid; D005947:Glucose; D006854:Hydrocortisone; D009638:Norepinephrine