Training quantification in endurance sports: training load and the acute performance secrement

The aim of the thesis was to obtain a better understanding into current measurements of Training Load (TL) in endurance performance and whether these TL metrics estimate the training stress imposed by endurance exercise.

In the first study of the thesis (Chapter 3), the concept of Acute Performance Decrement (APD) was introduced. 14 recreational and competitive cyclists were asked to perform a 5 min TT as a baseline, and after various cycling training sessions. The cycling training sessions consisted of a 5 min TT, a 20 min TT, a 20 min and a 40 min sub-maximal cycling session. The resulting APD was calculated as the percentage change in 5 min TT from baseline and was compared with the TL metrics from the corresponding training sessions. The results shown that an APD was found after all training sessions (ηp2=0.971; P<0.001). A similar APD was observed after the 5 and a 20 min sessions that contradicted the TL metrics. These findings suggest that the basis for TL metrics may be flawed. The

TL metrics based on the concept of TWD did not agree with how APD responded after the various cycling training sessions.

In the second study (Chapter 4), the concept of APD was investigated in running. The aim of the study was to investigate whether TL responses were in an agreement with APD. 11 well-trained runners were asked to perform a 1500m TT as a baseline, and after various running sessions. Continuous (CON) and intermittent (INT) running bouts of different duration were examined. The running sessions consisted of either maximal effort for 10 min (10CON, 10INT) or sub-maximal for 25 min (25CON, 25INT). The results showed that an APD was found after all training sessions. TL metrics showed the opposite response compared to APD. APD was found to be similar when compared after the training sessions, with differences found only after 10INT vs 25CON (P=0.02). In contrast, TL metrics provided the opposite pattern with higher scores observed for CON vs INT and lower scores for 10 min vs 25 min training sessions (P<0.001; ηp2 =0.563).

In the third study (Chapter 5), APD and TL metrics were examined after running at two different intensities and two durations. 12 trained runners were asked to perform a 1500m TT as a baseline and after 4 training sessions. The training sessions consisted for two different intensities (RPE of 5 and 8) and durations (10 min and 40 min). APD was calculated as the percentage change in 1500m TT. The results showed that the training sessions that lasted for 40 min resulted in greater TL metric scores compared to those that lasted for 10 min (P<0.001; ηp2 >0.781). In contrast, APD was found to be similar after the 10 min (RPE 8) and 40 min (RPE 5) training sessions (P > 0.99).

The findings from this thesis demonstrated that training stress as indicated by APD occurs in response to a combination of exercise intensity and duration that is not reflected by most TL metrics. Across all studies, the magnitude of APD was found to depend mainly on how intense the exercise dose was, however, extended exercise durations were found to increase the training stress. In all experimental studies, an agreement between TL metrics and APD was not found. These findings may provide concern for the validity of the TL metrics but may pave the road for the development of new TL metrics. It is suggested that new TL metrics are required that need to account for the effects of intensity and duration and their interaction.