PMID 35646132

Research
All papers

Effects of aquatic high-intensity interval training and moderate-intensity continuous training on central hemodynamic parameters, endothelial function and aerobic fitness in inactive adults

Tang S, Huang W, Wang S, Wu Y, Guo L, Huang J, Hu M

Question

How do 6 weeks of aquatic HIIT and moderate-intensity continuous swimming affect central hemodynamics, endothelial function, and aerobic fitness in inactive adults?

Summary

In inactive adults, 6 weeks of aquatic HIIT and aquatic moderate continuous training both improved some body composition and vascular measures. HIIT used only 6 minutes of hard swimming per session and improved VO2max and flow-mediated dilation, while MICT produced stronger blood-pressure and resting heart-rate reductions.

Methodology

  • 31 inactive adults randomized; 26 analyzed after attendance exclusion.
  • 31 participants.
  • Breaststroke swimming.
  • Work intervals: 30 s.
  • Recovery: 60 s rest.
  • Intensity: 75-90% HRmax week 1; 95% HRmax and RPE 15-18/20 weeks 2-6.
  • 18-20 min training segment; about 53-55 min including warm-up/cool-down.
  • 3 sessions/week.
  • 6 weeks.
  • Randomized controlled active-comparator trial
  • VO2max, Vascular function, Body composition, and Metabolic markers were tracked.

Outcomes

VO2max

HIIT improved absolute and relative VO2max; MICT did not.

HIIT relative VO2/kg 30.9 +/- 6.2 to 33.5 +/- 6.4; group x time p<0.05.

Improved

FMD

FMD improved after aquatic exercise, with clearer significance in HIIT.

HIIT FMD 3.56 +/- 1.67 to 4.94 +/- 2.10, p<0.05; MICT p=0.072.

Improved

Blood pressure

MICT reduced central and peripheral blood pressure more consistently than HIIT.

MICT reduced bSBP, bDBP, aSBP, aDBP, aMP, and HR; HIIT reduced aMP only.

Mixed

Body composition

Both groups reduced weight, BMI, and fat mass; HIIT also increased skeletal muscle and reduced fat percentage.

HIIT fat % p<0.001 and skeletal muscle p<0.01; MICT fat % not significant.

Improved

Insights

  • Aquatic HIIT delivered 6 minutes of hard work per session with measurable aerobic and endothelial gains.
  • MICT may be a better short-term aquatic option when blood-pressure reduction is the priority.
  • Water-based HR targets may need validation for each user.

Limitations

  • Small sample.
  • Short intervention.
  • Five participants excluded for low attendance.
  • Land-derived HRmax may not map cleanly to water exercise.
  • No explicit adverse-event reporting.

Safety

  • No explicit adverse-event report was found.
  • Participants with severe respiratory disease, kidney dysfunction, or cardiovascular disease were excluded.
  • Floats could be used to assist swimming.