PMID 37834790

Research
All papers

Minimal Detectable Change in Resting Blood Pressure and Cardiorespiratory Fitness: A Secondary Analysis of a Study on School-Based High-Intensity Interval Training Intervention

Domaradzki J

Question

What are the MDC90 thresholds for resting blood pressure and fitness index in adolescents undergoing school-based HIIT, and do HIIT-induced changes exceed them?

Summary

This secondary analysis used a school-based Tabata-style HIIT study in adolescents to estimate minimal detectable changes for blood pressure and a Harvard Step Test fitness index. The average HIIT changes improved systolic blood pressure and fitness versus control, but most individuals did not exceed the MDC thresholds.

Methodology

  • Secondary school adolescents from one urban school
  • 141 participants.
  • Bodyweight circuit.
  • Work intervals: 20 seconds.
  • Recovery: 10 seconds plus 1-minute breaks between three sessions.
  • Intensity: 75-80% HRmax; achieved mean HR 156.2 +/- 17.8 bpm.
  • 14 minutes.
  • 1 session/week.
  • 10 weeks.
  • Preplanned secondary analysis of a two-group school-based experimental study
  • Systolic blood pressure, Diastolic blood pressure, Fitness index, and Minimal detectable change were tracked.

Outcomes

SBP

Experimental group SBP decreased more than control.

Delta -6.31/-6.32 vs 0.75, p<0.001, d=-1.02.

Improved

DBP

DBP change did not differ significantly between groups.

Delta -2.36 vs 0.79, p=0.107.

No clear change

Fitness index

Fitness index improved more than control.

Delta 2.36 vs 0.35, p=0.002, d=0.54.

Improved

MDC90

MDC thresholds were high and many individuals did not exceed them.

MDC90 SBP 7.82 mmHg, DBP 12.45 mmHg, FI 5.39; 34.25%, 5.48%, and 21.92% exceeded thresholds respectively.

Mixed

Insights

  • Short bodyweight Tabata blocks can fit inside school PE.
  • Progress metrics should account for measurement error and individual variability.
  • Once-weekly dose may be too low for consistent individual responses.

Limitations

  • Secondary analysis.
  • One school and homogeneous age.
  • Sexes pooled due sample size.
  • Harvard Step Test fitness index less precise than VO2max.
  • Internal inconsistency in text about average MDC exceedance.

Safety

  • Adverse events were not reported.
  • Students with medical contraindications to PE were excluded and parental/legal guardian consent was required.
  • Intensity was monitored with Polar H1 heart-rate monitors during the PE-class HIIT.
  • Of 187 initial adolescents, 10 were excluded for medical contraindication, 17 for additional sports training, and 19 during intervention for PE-class absence.