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Positron emission tomography detects greater blood flow and less blood flow heterogeneity in the exercising skeletal muscles of old compared with young men during fatiguing contractions
Author(s) -
Rudroff Thorsten,
Weissman Jessica A.,
Bucci Marco,
Seppänen Marko,
Kaskinoro Kimmo,
Hein Ilkka,
Kalliokoski Kari K.
Publication year - 2014
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2013.264614
Subject(s) - isometric exercise , blood flow , medicine , hyperaemia , skeletal muscle , positron emission tomography , cardiology , anatomy , nuclear medicine
Key points The results of previous studies that attempted to demonstrate the effects of ageing on skeletal muscle blood flow are controversial because these studies used indirect assessments of skeletal muscle blood flow obtained via whole limb blood flow measurements that provide no information on the distribution of blood flow within particular muscles. We used positron emission tomography to measure blood flow per gram of muscle in old and young men with similar levels of physical activity. Resting muscle blood flow was similar in both groups and exercising muscle blood flow was greater and less heterogeneous in the older men. Old and young men achieved similar maximal voluntary contraction forces and endurance times during two types of fatiguing isometric task. These findings indicate that physically active old men have intact neural drive to the muscle and achieve adequate exercise hyperaemia despite the age‐induced decrease in their muscle volume.Abstract The purpose of this study was to investigate blood flow and its heterogeneity within and among the knee muscles in five young (26 ± 6 years) and five old (77 ± 6 years) healthy men with similar levels of physical activity while they performed two types of submaximal fatiguing isometric contraction that required either force or position control. Positron emission tomography (PET) and [ 15 O]‐H 2 O were used to determine blood flow at 2 min (beginning) and 12 min (end) after the start of the tasks. Young and old men had similar maximal forces and endurance times for the fatiguing tasks. Although muscle volumes were lower in the older subjects, total muscle blood flow was similar in both groups (young men: 25.8 ± 12.6 ml min −1 ; old men: 25.1 ± 15.4 ml min −1 ; age main effect, P = 0.77) as blood flow per unit mass of muscle in the exercising knee extensors was greater in the older (12.5 ± 6.2 ml min −1 (100 g) −1 ) than the younger (8.6 ± 3.6 ml min −1 (100 g) −1 ) men (age main effect, P = 0.001). Further, blood flow heterogeneity in the exercising knee extensors was significantly lower in the older (56 ± 27%) than the younger (67 ± 34%) men. Together, these data show that although skeletal muscles are smaller in older subjects, based on the intact neural drive to the muscle and the greater, less heterogeneous blood flow per gram of muscle, old fit muscle achieves adequate exercise hyperaemia.