Author(s): YEH, K.T., CHENG, H., TSAI, S., LIU, H., Institution: NATIONAL TAIWAN NORMAL UNIVERSITY, Country: TAIWAN, Abstract-ID: 826

INTRODUCTION:
The correlation between external load, such as exercise work rate (WR) and exercise density (ED), which incorporate exercise duration into calculation, with internal load, such as lactate levels and session rating of perceived exertion (sRPE), is evident. Existed studies in the relationship between external and internal load are still a lack of different inter-set rest intervals and training to failure. Therefore, this study aimed to assess the relationship between external and internal load in resistance training with different inter-set rest intervals and training to failure.
METHODS:
Healthy young males (n = 18; age = 22.9 ± 1.9 years; weights = 69.7 ± 5.9 kg) completed four trials, namely resistance exercise with short (60 seconds), medium (120 seconds), and long rest (180 seconds) interval and training to failure (120 seconds rest interval). The prescription consisted of squat, bench press, and deadlift, performed for 3 sets of 7 repetitions (70% of 1RM). Blood lactates were measured before and after exercise. sRPE was assessed 30 minutes post-exercise. External load calculations included WR(VL) = (load × repetitions × sets) ÷ exercise time (kg/min), WR(J) = (load × repetitions × sets × distance) ÷ exercise time (joules/min), and Exercise density (ED) = (load × repetitions × sets) ÷ total rest interval time (kg/min).
RESULTS:
sRPE and changes in blood lactate concentration were higher in short rest interval compared to long rest interval, and in failure trial compared to non-failure trial (p < 0.05). WR (VL), WR (J), and ED decreased with inter-set rest intervals. WR (VL), WR (J), and ED in the failure trial were higher than medium and long rest intervals, whereas ED in the failure trial was significantly lower than short rest interval (p < 0.05). Moderate correlations were found between external load and sRPE (p < 0.05, r = 0.303-0.406) and changes in blood lactate concentration (p < 0.05, r = 0.416-0.498).
CONCLUSION:
The relationship between external and internal load in resistance training with different inter-set rest intervals and training to failure further ensured the reliability of external load to monitor the training dose.