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Skeletal muscle adaptation in adolescent boys
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1982
Year
The study examined how 3‑month sprint versus endurance training altered vastus lateralis muscle fiber size and glycolytic (PFK) and oxidative (SDH) enzyme activities in adolescent boys. The authors measured PFK and SDH activities at baseline, after 3‑month training, and following a 6‑month detraining period. Endurance training raised VO₂max, type‑ST and type‑FTa fiber area, and SDH activity, all of which returned to baseline after detraining, whereas sprint training only increased PFK activity, which also disappeared after detraining; thus, enzyme adaptations were training‑mode specific and mirrored adult patterns in direction but differed in magnitude.
The purpose of the present study was to investigate the effects of 3-month sprint and endurance training programs on the vastus lateralis muscle fiber area and the activities of glycolytic (phosphofructokinase; PFK) and oxidative (succinate dehydrogenase; SDH) enzymes of adolescent boys. Enzyme activities were also determined after a subsequent 6-month detraining period. Endurance training resulted in significant increases in V̇o2max (58.4 to 64.3 ml·min-1·kg-1), in ST and FTa fiber area (6.0 to 7.3 and 8.0 to 10.4 μm2 × 103, respectively), and in SDH activity (6.4 to 9.1 IU). After detraining, V̇O2max and SDH activity returned to pre-training levels. Sprint training resulted in a significant increase only in PFK activity (28.1 to 33.9 IU), which was also abolished in the detraining period. These data demonstrate that in adolescent boys skeletal muscle enzyme changes are specific to the mode of training and that they are similar in direction but different in magnitude to those found in adults.