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Publication Date


First Advisor

Jim Johnson

Document Type

Masters Thesis

Degree Name

Master of Science


Biological Sciences


Swimming-Crawl stroke, Swimming-Equipment and supplies, Center mount snorkel, Freestyle, Swimming, Stroke index, Efficency


Snorkels have been around for thousands of years and now include a snorkel that is mounted in the center of the face, a piece of equipment utilized by current competitive swimmers of all ages and skill levels. According to center mounted snorkel manufacturers and many coaches, snorkels improve swimmers’ stroke efficiencies in freestyle by eliminating the need to turn the head to breathe and are used in training for this purpose. Despite the prevalence and acceptance of the snorkel in swim training, little research exists that examines if snorkels actually do benefit swimmers. The purpose of this study was to determine if there are effects of snorkel use on freestyle swimming efficiency, as approximated by stroke index.

Eleven subjects, all competitive swimmers on Smith College’s women’s swim team, participated in this study. Subjects completed four testing sessions of a 100-yard freestyle maximal effort swim with a center mount snorkel and a 100-yard freestyle maximal effort swim without a snorkel. During the sessions each subject wore a Triton unit attached to their goggles underneath their swim cap. The Triton unit collected data on stroke length, stroke rate, stroke count, velocity, split times, and stroke index for each length of the pool completed by the swimming subjects.

The data analysis concluded that there was a significant difference in the efficiency of the subjects between the snorkel swimming and regular swimming testing conditions. The subjects’ stroke index value for snorkel swimming was significantly less than the stroke index value for regular swimming (p-value = 0.012) meaning the swimmers’ stroke efficiency declined with the snorkel (snorkel 2.56±0.47; no snorkel 2.77±0.46). Stroke length, a component of stroke index, was also found to have a statistically significant difference between testing conditions (p-value = 0.006), specifically decreasing when swimmers used a snorkel (snorkel 0.94±0.15; no snorkel 1.01±0.18). Stroke count, number of strokes per length of the pool, was found to increase significantly (p-value = 0.016) when a snorkel was worn (snorkel 18.7±2.8; no snorkel 17.6±2.4). Stroke rate however showed no significant differences when swimmers used or did not use a snorkel (snorkel 1.43±0.22; no snorkel 1.48±0.19). These observed changes in efficiency and stroke parameters resulting from snorkel use indicate that snorkels likely do not improve the efficiency of swimmers.




54 pages : illustrations (some color). Includes bibliographical references (pages 45-47.