REF-1433 · Svedenhag & Seger, 1992 · Medicine and Science in Sports and Exercise · Paper · PubMed

What heart rate should I aim for when I run in the pool?

Lower than on land: in 10 trained runners heart rate ran 8-11 bpm lower in water at equal oxygen uptake (max 172 vs 188); ~10 bpm is our rounding of group means. 1992, abstract.

Main caveat: Abstract only; no SDs or individual data.
limited evidenceMeasured on trained to highly trained athletes

Svedenhag and Seger (Huddinge University Hospital, Sweden) studied how water immersion changes the cardiorespiratory and lactate responses to running.

Ten trained runners (mean age 26) wearing a buoyant vest ran in water at four submaximal loads set by target heart rates of 115, 130, 145 and 155-160 beats/min and at maximal intensity, and the values were compared with treadmill running. At a given VO2, heart rate was 8-11 beats/min lower in water than on the treadmill, irrespective of intensity.

Maximal oxygen uptake (4.03 vs 4.60 L/min) and maximal heart rate (172 vs 188 beats/min) were lower in water. Perceived exertion (legs and breathing) and RER were higher in submaximal water running, ventilation was similar, and blood lactate was consistently higher in water, whether related to VO2 or to %VO2max.

The authors read this as immersion-induced cardiac adjustments that extend up to maximal exercise, with the hydrostatic load and an altered running technique adding anaerobic metabolism.

Our reading: the number behind "set water heart-rate targets lower than land targets": at the same oxygen uptake heart rate was about 10 bpm lower and the maximum 16 bpm lower (our arithmetic), while the effort felt harder — so land heart rate, if held in water, overshoots the intended oxygen uptake at submaximal intensities and cannot be reached near the top, and land RPE, if held in water, undershoots it.

It is an old study (1992); newer work outside the base (Nakanishi 1999, Dowzer 1999) also found much lower maximal heart rate in deep water, and a later review (Killgore 2012) that the gap shrinks with experience.

Protocol

Participants: n = 10 trained runners, mean age 26 years (men by PubMed indexing).
Water running: with a buoyant vest, at four submaximal loads set by target heart rate (115, 130, 145 and 155-160 beats/min) and at maximal intensity.
Land comparison: treadmill running, with values compared at a given VO2 and %VO2max.
Measures: VO2, heart rate, perceived exertion (legs and breathing), blood lactate, RER, ventilation.
Funding and interests: PubMed lists "Research Support, Non-U.S. Gov't"; no funder named and no conflict statement in the abstract record.

Key Results

MeasureWater (vest)Treadmill
Heart rate at a given VO28-11 beats/min lower, irrespective of intensityreference
Maximal VO2 (L/min)4.034.60
Maximal heart rate (beats/min)172188
Perceived exertion, legs and breathing (submaximal)higher—
RER (submaximal)higher—
Ventilation (L/min)similarsimilar
Blood lactate, at a given VO2 and %VO2maxconsistently higher—
Not in the abstract: SDs, individual differences, the RPE values, water temperature.

Mechanisms

Measured: lower heart rate at the same VO2 at every intensity, lower maximal VO2 and heart rate, higher perceived exertion, RER and lactate in water.
Authors' interpretation: immersion induces acute cardiac adjustments (in line with earlier cycle-ergometer studies in water) that extend to maximal exercise; the external hydrostatic load and an altered running technique add anaerobic metabolism during supported water running.
Inference: hydrostatic pressure moves blood toward the chest and raises stroke volume, so the same cardiac output needs fewer beats; the arms and a different leg action in water recruit muscle less economically, which fits the higher lactate and exertion.

Practical Application

What heart rate should I aim for when I run in the pool? Lower than on land: in 10 trained runners heart rate ran 8-11 bpm lower in water at equal oxygen uptake (max 172 vs 188); ~10 bpm is our rounding of group means. 1992, abstract.
Set the dose by structure and effort, with lowered heart-rate targets: land heart-rate zones overshoot in water at submaximal intensities and cannot be reached at the top; land RPE, held in water, may undershoot because submaximal water running felt harder (the abstract does not say the RPE comparison was at equal oxygen uptake; REF-1438 measured the undershoot in recreational runners).The "~10 bpm lower" target is our rounding of this study's 8-11, not a tested prescription.
The base's operational deep-water line needs this caveat: REF-922 keeps fitness "provided the water sessions carry the same duration and intensity as the runs they replace"; same intensity cannot be set from land heart rate, and recreational runners steering by feel ran at a lower intensity (REF-1438).
What it does not show: training effects, women, runners new to water running, water running without a vest.

Limitations

Abstract only; no SDs or individual data.
Ten men, trained runners; experience with water running not stated in the abstract.
Buoyant vest only; water temperature not given in the abstract.
Acute responses; no training outcome.
Old study (1992); later deep-water studies outside the base found similar or larger maximal gaps.
Funding: "Research Support, Non-U.S. Gov't" per PubMed; no conflict statement in the record.
How this entry was checked and changed
Why this level

(from the abstract) — a within-subject comparison of 10 (the rubric's B for crossovers under 15); one sex (men by PubMed indexing), one laboratory, 1992