WITHDRAWN: The decrement in swimming performance following an increase in training volume is associated with muscle fibre typology

Abstract

<h2>Abstract</h2><h3>Objectives</h3> We examined if muscle fibre typology (MFT) was associated with the magnitude of change in performance following alterations in swimming training volume in highly-trained swimmers. <h3>Design</h3> Single group intervention. <h3>Methods</h3> Ten swimmers (<i>n</i> = 2 female) completed four consecutive training phases: i) 2-wk normal training (NT); ii) 1-wk decrease (DEC1; 30 % decrease in volume) iii) 3-wk higher-volume training (HVT; i.e., 25 % increase from NT), and iv) 1-wk decrease (DEC2; 30 % decrease in volume). Swimmers performed a 200-m freestyle time trial (200-m TT), assessments of lower and upper-body power and a 10- and 30-s maximal tethered swimming test in the 2 days directly following each training phase. MFT of the gastrocnemius and soleus was estimated by quantification of muscle carnosine concentration using proton magnetic resonance spectroscopy in the week post-DEC2 and expressed as a carnosine aggregated z-score (CAZ-score). <h3>Results</h3> Some, but not all, performance-related and physical tests were affected by alterations to training volume. The relative increase in the 200-m TT time (i.e., slower time) from DEC1 (2:13.3 ± 00:07.3 m:ss.0) to HVT (2:16.0 ± 00:08.4) was associated with CAZ-score (<i>r</i> = 0.697, <i>p</i> = 0.025). 200-m TT performance was restored following DEC2 but there was no performance supercompensation. <h3>Conclusion</h3> The results of this study suggest that swimmers with a greater estimated proportion of type I fibres were better able to tolerate a short-term period of increased training volume. Nonetheless, a progressive decrease in training volume over 7 d was not sufficient to promote performance supercompensation in highly-trained swimmers.