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

PMID: 37834790
Journal: Journal of Clinical Medicine
Published: 2023 Sep 23
Authors: 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.

## Population

- Secondary school adolescents from one urban school
- Sample size: 141
- Age: About 16 years
- Sex: 52 boys and 89 girls
- Fitness level: School PE students; extra sports training excluded
- Health status: No medical contraindication to PE

## Methodology

- Preplanned secondary analysis of a two-group school-based experimental study
- 10 weeks
- Secondary school physical education classes in Wroclaw, Poland
- Randomized and controlled study design.

## Protocol

- School PE Tabata HIIT.
- Modality: Bodyweight circuit.
- Work intervals: 20 seconds.
- Recovery: 10 seconds plus 1-minute breaks between three sessions.
- Sets or repetitions: Three Tabata sessions: pushups/high knees, dynamic lunges/spider crawling, plank-to-pushups/side squeezes.
- Intensity: 75-80% HRmax; achieved mean HR 156.2 +/- 17.8 bpm.
- Session duration: 14 minutes.
- Frequency: 1 session/week.
- Program length: 10 weeks.
- Standard physical education.
- Modality: Usual school PE.
- Session duration: 45-minute PE lesson context.
- Frequency: School PE schedule.
- Program length: 10 weeks.

## Outcomes

### SBP
Status: improved
Experimental group SBP decreased more than control.

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

### DBP
Status: no clear change
DBP change did not differ significantly between groups.

Delta -2.36 vs 0.79, p=0.107.

### Fitness index
Status: improved
Fitness index improved more than control.

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

### MDC90
Status: mixed
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.

## Practical 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 And Adherence

- 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.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/37834790/) (pubmed)
- [DOI](https://doi.org/10.3390/jcm12196146) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10573284/) (full text)

## Agent Guidance

Preserve the paper-level scope of this note. Do not generalize beyond the population, protocol, measured outcomes, and limitations above.