Determination of the lactate threshold and maximal blood lactate steady state intensity in aged rats.
The reliability of the lactate threshold (LT) determined in aged rats and its validity to identify an exercise intensity corresponding to the maximal blood lactate steady state (MLSS) were analyzed. Eighteen male aged Wistar rats (approximately 365 days) were submitted to two incremental swimming tests until exhaustion, consisting of an initial load corresponding to 1% of body mass (BM) and increments of 1% BM at each 3-min with blood lactate ([lac]) measurements. The LT was determined by visual inspection (LT(V)) as well by applying a polynomial function on the [lac]/workload ratio (LT(P)) by considering the vertices of the curve. For the MLSS, twelve animals were submitted, on different days, to 3-4 exercise sessions of 30-min with workload corresponding to 4, 5 or 6% BM. The MLSS was considered the highest exercise intensity at which the [lac] variation was not higher than 0.07 mM.min(-1) during the last 20-min. No differences were observed for the test-retest results (4.9 +/- 0.7 and 5.0 +/- 0.8 %BM for LTv; and 6.0 +/- 0.6 and 5.8 +/- 0.6 %BM for LTp) that did not differ from the MLSS (5.4 +/- 0.5 %BM). The LT identified for aged rats in swimming, both by visual inspection and polynomial function, was reliable and did not differ from the MLSS.
Cunha
Rafael Rodrigues
RR
Catholic University of Brasilia, Graduate Program on Physical Education and Health, Taguatinga, DF, Brazil.
Cunha
Verusca Najara de Carvalho
VN
Segundo
Paulo Russo
PR
Moreira
Sérgio Rodrigues
SR
Kokubun
Eduardo
E
Campbell
Carmen Sílvia Grubert
CS
de Oliveira
Ricardo Jacó
RJ
Simões
Herbert Gustavo
HG
D000375:Aging / Q000378:metabolism*; D000704:Analysis of Variance; D000818:Animals; D019344:Lactic Acid / Q000097:blood* / Q000378:metabolism; D008297:Male; D015233:Models, Statistical; D010805:Physical Conditioning, Animal / Q000502:physiology; D005082:Physical Exertion / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D015203:Reproducibility of Results; D013550:Swimming
D019344:Lactic Acid