Unaccustomed High-Mileage vs Intensity Training-Related Changes in Performance and Serum Amino Acid Levels

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Abstract
To test the overtraining-related "imbalanced amino acid hypothesis" (19), the influence of an unaccustomed average 103 % 4 wk-1 increase in training mileage (ITV) on performance and on serum levels of individual amino acids (AAs) was examined in distance runners and controlled by an unaccustomed average 152 % · 4 wk-1 increase in tempo-pace and interval runs (ITI). Two mmol · l-1 lactate performance (2 LP) increased, 4 LP stagnated and total running distance (TD) decreased in the incremental test during ITV - which may indicate an ITV-dependent overtraining - in contrast to an ITI-related increase in 2 LP, 4 LP and TD. The summed serum AAs decreased in ITV (2744 ± 534 vs 2933 ± 663 umol · l-1; p < 0.05) in contrast to an ITI-related increase (3541 ± 657 vs 3252 ± 885 umol · l-1; p < 0.05) with an average 29) % higher final summed AAs concentration during ITI (p < 0.05). During ITV 12 individual AAs decreased by 6 -17 %, 8 remained constant and 3 increased (Cys, Met, fTrp) by 6 - 19 %, as opposed to an ITI-related increase in 16 AA by 6 - 55 %. The observed IPV-related changes in serum AAs profile were smaller than after completing contests as a marathon, a 100 km-runoran ultra-triathlon. It may be concluded that the observed small changes in AAs profile or AAA/BCAA and AA/LNAA ratios only represent an epiphenomenon without recognizable influence on incremental test performance, since increases in fTrp/LNAA ratios (+ 28 % in ITV vs + 45 % in ITI) were found to be related both to performance impairment (ITV) and improvement (ITI).

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