Open AccessEffect of speed endurance training and reduced training volume on running economy and single muscle fiber adaptations in trained runners
Author(s) -
Skovgaard Casper,
Christiansen Danny,
Christensen Peter M.,
Almquist Nicki W.,
Thomassen Martin,
Bangsbo Jens
Publication year - 2018
Publication title -
physiological reports
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.918
H-Index - 39
ISSN - 2051-817X
DOI - 10.14814/phy2.13601
Subject(s) - running economy , ucp3 , endurance training , vo2 max , muscle biopsy , glycogen , zoology , medicine , muscle fibre , training (meteorology) , physical therapy , cardiology , endocrinology , chemistry , skeletal muscle , biology , heart rate , uncoupling protein , biopsy , physics , blood pressure , obesity , meteorology , brown adipose tissue
Abstract The aim of the present study was to examine whether improved running economy with a period of speed endurance training and reduced training volume could be related to adaptations in specific muscle fibers. Twenty trained male ( n = 14) and female ( n = 6) runners (maximum oxygen consumption (VO 2 ‐max): 56.4 ± 4.6 mL /min/kg) completed a 40‐day intervention with 10 sessions of speed endurance training (5–10 × 30‐sec maximal running) and a reduced (36%) volume of training. Before and after the intervention, a muscle biopsy was obtained at rest, and an incremental running test to exhaustion was performed. In addition, running at 60% vVO 2 ‐max, and a 10‐km run was performed in a normal and a muscle slow twitch ( ST ) glycogen‐depleted condition. After compared to before the intervention, expression of mitochondrial uncoupling protein 3 ( UCP 3) was lower ( P < 0.05) and dystrophin was higher ( P < 0.05) in ST muscle fibers, and sarcoplasmic reticulum calcium ATP ase 1 ( SERCA 1) was lower ( P < 0.05) in fast twitch muscle fibers. Running economy at 60% vVO 2 ‐max (11.6 ± 0.2 km/h) and at v10‐km (13.7 ± 0.3 km/h) was ~2% better ( P < 0.05) after the intervention in the normal condition, but unchanged in the ST glycogen‐depleted condition. Ten kilometer performance was improved ( P < 0.01) by 3.2% (43.7 ± 1.0 vs. 45.2 ± 1.2 min) and 3.9% (45.8 ± 1.2 vs. 47.7 ± 1.3 min) in the normal and the ST glycogen‐depleted condition, respectively. VO 2 ‐max was the same, but vVO 2 ‐max was 2.0% higher ( P < 0.05; 19.3 ± 0.3 vs. 18.9 ± 0.3 km/h) after than before the intervention. Thus, improved running economy with intense training may be related to changes in expression of proteins linked to energy consuming processes in primarily ST muscle fibers.