Exploring interindividual differences in fasting and postprandial insulin sensitivity adaptations in response to...

Area of Science:

• Exercise Physiology
• Metabolic Health
• Human Adaptation

Background:

• Previous research suggests individual variability in exercise training response, particularly for insulin sensitivity.
• However, these studies often overlook technical, biological, and random measurement errors.
• Understanding true trainability requires accounting for these error sources.

Purpose of the Study:

• To investigate interindividual variability in fasting and postprandial insulin sensitivity following low-volume sprint interval training (SIT).
• To determine if observed variations in response are due to inherent trainability or measurement error.

Main Methods:

• Pooled data from 63 untrained participants (49 SIT, 14 controls) over 6 weeks.
• Measured fasting and oral glucose tolerance test (OGTT)-derived insulin sensitivity markers pre- and post-intervention.
• Utilized the standard deviation of individual responses (SD_IR) to assess variability, accounting for measurement error.

Main Results:

• Positive SD_IR values for fasting glucose, 2-h OGTT glucose, glucose AUC, and Cederholm Index suggest potential individual responses.
• However, wide 95% confidence intervals (CIs) and crossing of zero for all variables indicate uncertainty in true interindividual differences.
• Only 2-22% of participants could be classified as responders/non-responders with high certainty.

Conclusions:

• Observed variations in insulin sensitivity following SIT cannot be definitively attributed to inherent trainability.
• High levels of technical, biological, and random error limit the confident identification of responders and non-responders.
• Accurate assessment of training adaptations necessitates rigorous error analysis.