Short reportChanges in skeletal muscle architecture following a cycloergometer test to exhaustion in athletes
Introduction
Muscle architecture is a primary determinant of muscle function.1, 2 The pennation angle (θ) is the angle of insertion of muscle fibre into the tendon aponeurosis. Ultrasound imaging accurately depicts fibre length and orientation, both in physiological and pathological conditions.2 Pennation angle decreases with aging,2 and there is a definite relationship between fibre pennation and muscle size, suggesting that muscle hypertrophy involves an increase in fibre pennation angles,3 even though a definite relationship between pennation and force generating capacity is not certain.4
We ascertained whether short-term exhaustive dynamic exercise induced changes in muscle architecture, as this variable is a major determinant of muscle function, and whether ultrasonography could be used to study acute muscular responses to exercise.
Section snippets
Subjects
Thirty-five male athletes (age 28.8 ± 9.8 years; height: 175.4. ± 5.5 cm; weight: 74 ± 11.5 kg; average years spent training: 11.1 ± 8.4 years; mean weekly duration of training: 10.4 ± 3.20 h) who underwent a pre-participation screening volunteered to participate in this study. Most of them were track and field athletes (16 subjects), five played Soccer, five were swimmers, four cycled and two undertook competitive aerobics, one Karate, one tennis and one rugby. All subjects were medically screened using a
Results
All the athletes stopped the test when exhausted, at a mean work rate of 221.9 ± 63.6 W and an exercise time of 18.75 ± 3.64 min. Lactic acid at rest was 2.3 ± 0.9 mmol/L; at exhaustion, 8.3 ± 4.16 mmol/L; after 5 min of recovery, 8.3 ± 3.05 mmol/L; and after 30 min it was 4.5 ± 2.2 mmol/L.
Serum CK at rest was of 83.13 ± 55.83 U/L and increased significantly after exercise, reaching values of 96.73 ± 61.59 U/L (p = 0.002).
Quadriceps thickness increased in all subjects, from 32.1 ± 3.3 mm at rest to 34.9 ± 3.00 mm after the test
Discussion
There are marked changes in intramuscular architecture of the quadriceps following a bout of cycloergometry to exhaustion, with significant increase of quadriceps thickness (Fig. 1) and pennation angle (Fig. 2). The increased muscle volume after exercise is probably a consequence of muscle oedema produced even by light workloads,6 and also a result of a slowing of muscle relaxation due to intracellular accumulation of Ca++ and H+. Elevation of the Ca++-dependent proteolytic pathway degrades
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