The Effects of Small Changes in Power Output Below and Above the Maximal Lactate Steady State in Performance Fatigability in Older Females and Males
Rafael de Almeida Azevedo, Guillaume Y. Millet, Juan M. MuriasPurpose:
In young adults, performance fatigability is affected by sex even with minor power output (PO) changes around the maximal lactate steady-state (MLSS). This study investigated whether these sex- and intensity-dependent effects persisted in older adults.
Methods:
9 females (65±5 yrs) and 10 males (67±4 yrs) performed three 30-min constant-PO exercise bouts at MLSS, 10 W below (MLSS−10), and 10 W above (MLSS+10), each followed by a time to task failure (TTF) test at 80% peak-PO. Performance fatigability was assessed via knee extensor isometric maximal voluntary contractions (IMVC), voluntary activation (VA), and potentiated 100 Hz doublet torque (Db100) before, immediately after the constant-PO and the TTF bouts.
Results:
IMVC declined less after MLSS−10 (-18±8%) than MLSS+10 (-22±8%; p=0.04), but neither differed from MLSS (-20±8%). Similarly, Db100 decline was smaller at MLSS−10 (-14±6%) than MLSS+10 (-19±9%; p=0.03) but similar to MLSS (-15±0%). VA decreases were similar across all intensities (-6-7%; p>0.05). No sex differences were found for any fatigability variables (p>0.05). Despite the shorter TTF with increased in intensity at the end of each 30-min constant-PO (p<0.001), performance fatigability parameters at failure were similar across conditions (p>0.05), without sex-related differences.
Conclusions:
Unlike previous reports in younger populations, older males and females exhibited similar fatigability profiles after slight manipulations in PO around the MLSS, suggesting sex-based differences in muscular endurance diminish with age.