PMID 34562202

Research
All papers

Six weeks of high-intensity interval training enhances contractile activity induced vascular reactivity and skeletal muscle perfusion in older adults

Herrod PJJ, Atherton PJ, Smith K, Williams JP, Lund JN, Phillips BE

Question

Does 6 weeks of time-efficient HIIT improve skeletal muscle microvascular responsiveness to acute contractile activity in healthy older adults?

Summary

This randomized controlled trial tested 6 weeks of fully supervised cycle-ergometer HIIT in healthy older adults aged 65-85 years. HIIT improved anaerobic threshold, dynamic exercise capacity, systolic blood pressure, and microvascular blood-volume response to a bout of knee-extension exercise, while the no-intervention control group did not change. The study had 100% HIIT session compliance but used a small, carefully screened healthy sample.

Methodology

  • Twenty-five healthy older adults aged 65-85 years randomized to HIIT or no-intervention control; 23 included in final analysis.
  • 25 participants.
  • Cycle ergometer.
  • Work intervals: 5 x 1-minute high-intensity cycling efforts.
  • Recovery: Recovery period included but not specified in the text read.
  • Intensity: High intensity; 10% increase after 3 weeks if modified Borg RPE <=8.
  • Approximately 15 minutes.
  • 3 sessions per week.
  • 6 weeks.
  • Randomized controlled trial comparing 6-week fully supervised HIIT with a no-intervention control period.
  • Microvascular blood volume response, Anaerobic threshold, Dynamic exercise capacity, and Resting blood pressure were tracked.

Outcomes

Microvascular responsiveness

HIIT increased microvascular blood-volume response to acute knee-extension exercise; control did not change.

HIIT 1.8 +/- 0.6 to 2.3 +/- 0.8, p < 0.01; control p = 0.94; interaction p < 0.01.

Improved

Anaerobic threshold

HIIT increased anaerobic threshold.

13.2 +/- 3.4 to 15.3 +/- 3.8 mL/kg/min, p < 0.01.

Improved

Dynamic exercise capacity

HIIT increased peak wattage during CPET.

145 +/- 60 to 159 +/- 59 W, p < 0.01.

Improved

Blood pressure

HIIT reduced systolic blood pressure but did not significantly change diastolic blood pressure.

SBP 142 +/- 16 to 133 +/- 11 mmHg, p < 0.01; DBP time p = 0.27 and interaction p = 0.76.

Mixed

Insights

  • Short cycling HIIT can improve fitness and vascular responsiveness in carefully screened older adults.
  • Clinical safety monitoring in this study was much higher than typical consumer settings.
  • Microvascular benefits are mechanistic and need clinical outcome confirmation.

Limitations

  • Small sample.
  • Healthy older adults only.
  • Strict exclusions for diabetes, active CVD, uncontrolled hypertension, and high BMI.
  • CEUS chronic baseline comparisons need validation.
  • Clinical significance of MBV response change is unknown.

Safety

  • All HIIT sessions were supervised with 12-lead ECG, BP, and pulse oximetry.
  • One MBF measurement failed because of cannula failure causing contrast extravasation.
  • No exercise adverse events were reported in the read text.