Adaptations in Capillarization and Citrate Synthase Activity in Response to Endurance Training in Older and Young Men
ABSTRACT The time-course of adaptation in cardiorespiratory fitness, measures of capillarization, and citrate synthase (CS) activity were examined in seven older (O; 69 ± 7 years) and seven young (Y; 22 ± 1 years) men pre-, mid-, and posttraining during a 12-week endurance training program. Training was performed on a cycle ergometer three times per week for 45 minutes at ~70% of maximal VO(2) (VO(2max)). VO(2max) and maximal cardiac output increased similarly from pre- to posttraining in O and Y (p < .05), and maximal a-vO(2diff) was greater (p < .05) posttraining in O and Y. CS was elevated at mid- and posttraining compared with pretraining in both O and Y (p < .05). Indices of capillarization increased 30%-40% in O and 20%-30% in Y and were elevated at posttraining compared with pre- and midtraining in both groups (p < .05). This study showed that both O and Y undertaking similar endurance training displayed capillary angiogenesis and improved mitochondrial respiratory capacity.
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ABSTRACT: Citrate synthase (CS) activity is a validated biomarker for mitochondrial density in skeletal muscle. CS activity is also used as a biochemical marker of the skeletal muscle oxidative adaptation to a training intervention, and a relationship between changes in whole body aerobic capacity and changes in CS activity is often assumed. However, this relationship and absolute values of CS and maximal oxygen uptake (V.O2max) has never been assessed across different studies. A systematic PubMed search on literature published from 1983 to 2013 was performed. The search profile included: citrate, synthase, human, skeletal, muscle, training, not electrical stimulation, not in-vitro, not rats. Studies that reported changes in CS activity and V.O2max were included. Different training types and subject populations were analyzed independently to assess correlation between relative changes in V.O2max and CS activity. 70 publications with 97 intervention groups were included. There was a positive (r = 0.45) correlation (P < 0.001) between the relative change in V.O2max and the relative change in CS activity. All reported absolute values of CS and V.O2max did not correlate (r =- 0.07, n = 148, P = 0.4). Training induced changes in whole body oxidative capacity is matched by changes in muscle CS activity in a nearly 1:1 relationship. Absolute values of CS across different studies cannot be compared unless a standardized analytical method is used by all laboratories.International Journal of Physiology, Pathophysiology and Pharmacology 01/2014; 6(2):84-101.
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ABSTRACT: This study examined the effects of age and training status on the pulmonary oxygen uptake (VO2p) kinetics of untrained and chronically trained young, middle-aged and older groups of men.Medicine & Science in Sports & Exercise 05/2014; DOI:10.1249/MSS.0000000000000398 · 4.46 Impact Factor
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ABSTRACT: It has been proposed that the adjustment of oxygen uptake (VO2) during the exercise on-transient is controlled intracellularly in young, healthy individuals, and that insufficient local O2 delivery plays a rate-limiting role in aging and disease only. This review shows that adequate O2 provision to the active tissues is critical in the dynamic adjustment of oxidative phosphorylation even in young, healthy individuals.Summary for Table of Contents This review illustrates the critical role of muscle oxygen delivery in the adjustment of oxidative phosphorylation during the exercise on-transient.Exercise and sport sciences reviews 11/2013; DOI:10.1249/JES.0000000000000005 · 4.82 Impact Factor