Maximum Sustained Fin-Kick Thrust Underwater

By Rubicon Foundation editorial team

6 min read · 24 October 2026

Maximum sustained fin-kick thrust in underwater swimming is a 1995 journal article by Yamaguchi H, Shidara F, Naraki N and Mohri M. Published in Undersea & hyperbaric medicine, it addresses the production of sustained thrust by fin-kicking underwater—a subject central to swimming performance, diver mobility and the demands of moving through water.

What does sustained fin-kick thrust mean?

Thrust is the forward force generated when a swimmer moves water with the legs and fins. A fin converts muscular movement into water displacement: its shape, stiffness and motion influence how effectively a kick produces propulsion.

“Sustained” distinguishes continuing effort from a brief burst. A diver may need to swim steadily rather than accelerate momentarily, so the capacity to maintain useful thrust involves both the force produced by each kick and the ability to repeat that movement over time.

The article’s subject therefore sits at the intersection of human physiology and underwater mechanics. It concerns how the body and fin work together in an environment where water resistance makes movement substantially different from walking or running.

Why is propulsion different underwater?

Water is denser than air, so moving a body through it creates considerable resistance. As swimming speed rises, drag increases sharply; posture, exposed area and movement technique all affect how much effort is needed to make progress.

Fin-kicking also asks the muscles to work against the resistance of the water during repeated leg movements. The diver’s breathing equipment and other carried gear can add load or alter balance, while buoyancy and trim influence whether effort goes into forward travel or unwanted vertical and sideways movement.

These interactions make underwater propulsion a practical problem as well as a matter of athletic performance. Efficient movement can help a diver manage a task or cover distance without unnecessary exertion, although the demands vary with conditions, equipment and individual capability.

Which physiological ideas help frame the question?

Muscular power and endurance are related but distinct. A short, forceful effort depends on producing high force quickly; sustained swimming requires repeated contractions and the capacity to continue working as fatigue develops.

Exercise underwater also takes place within the particular constraints of diving. Immersion changes how the body handles blood flow and heat, while breathing through diving equipment adds a respiratory workload. The balance between effort, breathing and available reserves matters whenever a diver is physically active.

Thrust: forward force generated through interaction between the fin and water.
Drag: resistance to movement, influenced by speed, posture and exposed area.
Fatigue: the decline in capacity to maintain muscular work.
Efficiency: how effectively effort produces useful movement rather than wasted motion.
Workload: the combined physical and respiratory demands of swimming underwater.

Why does this matter to divers and clinicians?

For divers, propulsion affects the ability to move while carrying equipment, maintain position and respond to changing task demands. Poorly matched effort and technique can lead to tiring quickly, especially when conditions make swimming more difficult or the diver must continue working for an extended period.

For diving physicians and hyperbaric clinicians, exercise capacity is part of understanding how divers tolerate work underwater. A discussion of fin-kick thrust connects physical performance with workload management; it does not replace an individual assessment of fitness, symptoms or fitness to dive.

Scientific divers may also need to move while carrying out observations or handling equipment. In that setting, propulsion is part of working effectively underwater, alongside buoyancy control, safe task planning and attention to the limits imposed by the environment.

How does the topic fit into diving research?

Research on underwater swimming draws together biomechanics, exercise physiology and equipment considerations. Measuring or characterising propulsion offers a way to examine how movement produces force, while the idea of sustained effort brings endurance and fatigue into the same practical question.

That broader perspective helps distinguish the ability to generate thrust from the ability to keep doing so. Both are relevant to underwater mobility, but neither alone describes a diver’s overall safety or performance: conditions, breathing, buoyancy, technique and task demands also shape the experience.

The publication appeared in Undersea & hyperbaric medicine in 1995, placing its subject within the wider scientific interest in human performance in aquatic and diving environments. Its title identifies a focused question about fin-driven movement and sustained force, a topic that remains relevant wherever divers must propel themselves through water.

Frequently asked questions

What is fin-kick thrust?

It is the forward force created when fin movement pushes water. The resulting propulsion depends on the interaction of the diver’s movement, the fin and water resistance.

Why distinguish sustained thrust from a brief burst?

A brief burst concerns a short, forceful effort, while sustained thrust concerns continued propulsion. Divers may need to maintain movement over time, making endurance and fatigue relevant alongside force.

Does fin-kick performance alone determine diving safety?

No. Underwater swimming is affected by conditions, equipment, buoyancy, technique, breathing workload and the task. Questions about personal fitness or symptoms should be discussed with a diving-medicine physician.

Citation details

Title: Maximum sustained fin-kick thrust in underwater swimming
Authors: Yamaguchi H, Shidara F, Naraki N, Mohri M
Year: 1995
Published in: Undersea & hyperbaric medicine : journal of the Undersea and Hyperbaric Medical Society, Inc 22(3)
Identifiers: PMID 7580765
Record type: Journal article
Repository record: Rubicon Research Repository, handle 123456789/2219

This page is an original summary written by the Rubicon editors from the publication’s bibliographic record. It does not reproduce the paper, its abstract or its data; consult the publication itself for its methods and findings.