Concentric resistance training increases muscle strength without affecting microcirculation.
OBJECTIVE
While the evidence is conclusive regarding the positive effects of endurance training, there is still some controversy regarding the effects of resistance training on muscular capillarity. Thus, the purpose was to assess whether resistance strength training influences resting skeletal muscle microcirculation in vivo.


METHODS
Thirty-nine middle-aged subjects (15 female, 24 male; mean age, 54+/-9 years) were trained twice a week on an isokinetic system (altogether 16 sessions lasting 50 min, intensity 75% of maximum isokinetic and isometric force of knee flexors and extensors). To evaluate success of training, cross-sectional area (CSA) of the quadriceps femoris muscle and its isokinetic and isometric force were quantified. Muscular capillarization was measured in biopsies of the vastus lateralis muscle. In vivo, muscular energy and lipid metabolites were quantified by magnetic resonance spectroscopy and parameters of muscular microcirculation, such as local blood volume, blood flow and velocity, by contrast-enhanced ultrasound analyzing replenishment kinetics.


RESULTS
The significant (P<0.001) increase in CSA (60+/-16 before vs. 64+/-15 cm(2) after training) and in absolute muscle strength (isometric, 146+/-44 vs. 174+/-50 Nm; isokinetic, 151+/-53 vs. 174+/-62 Nm) demonstrated successful training. Neither capillary density ex vivo (351+/-75 vs. 326+/-62) nor ultrasonographic parameters of resting muscle perfusion were significantly different (blood flow, 1.2+/-1.2 vs. 1.1+/-1.1 ml/min/100g; blood flow velocity, 0.49+/-0.44 vs. 0.52+/-0.74 mms(-1)). Also, the intensities of high-energy phosphates phosphocreatine and beta-adenosintriphosphate were not different after training within the skeletal muscle at rest (beta-ATP/phosphocreatine, 0.29+/-0.06 vs. 0.28+/-0.04).


CONCLUSIONS
The significant increase in muscle size and strength in response to concentric isokinetic and isometric resistance training occurs without an increase in the in vivo microcirculation of the skeletal muscles at rest.
Weber
Marc-André
MA
Department of Diagnostic and Interventional Radiology, University of Heidelberg, Heidelberg, Germany. MarcAndre.Weber@med.uni-heidelberg.de
Hildebrandt
Wulf
W
Schröder
Leif
L
Kinscherf
Ralf
R
Krix
Martin
M
Bachert
Peter
P
Delorme
Stefan
S
Essig
Marco
M
Kauczor
Hans-Ulrich
HU
Krakowski-Roosen
Holger
H
D000255:Adenosine Triphosphate / Q000378:metabolism; D001706:Biopsy; D001783:Blood Flow Velocity; D003287:Contrast Media / Q000008:administration & dosage; D005260:Female; D006801:Humans; D050356:Lipid Metabolism / Q000502:physiology; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008297:Male; D008833:Microcirculation; D008875:Middle Aged; D053580:Muscle Strength / Q000502:physiology*; D018482:Muscle, Skeletal / Q000098:blood supply / Q000000981:diagnostic imaging / Q000502:physiology*; D010101:Oxygen Consumption / Q000502:physiology; D010725:Phosphocreatine / Q000378:metabolism; D011134:Polysaccharides / Q000008:administration & dosage; D055070:Resistance Training / Q000379:methods*; D014463:Ultrasonography
D003287:Contrast Media; D011134:Polysaccharides; D010725:Phosphocreatine; C059891:SHU 508; D000255:Adenosine Triphosphate