Manual Dexterity in Open-Water Wetsuited Swimmers: A Cohort Crossover Study

Laboratory studies have demonstrated that manual dexterity decreases with increasing cold, which may adversely affect performance. Dexterity may be impaired by cooling of the hand, cooling of the lower motor neurons, and cognitive impairment. Wetsuits are commonly used in open-water swimming and are mandated in some situations. This study investigates the effects of cold-water wetsuited swimming on dexterity.

Five male and 4 female trained swimmers were recruited for this cohort crossover study. Following dual-energy X-ray absorptiometry scans to determine body composition, they swam in a freshwater lake on 7 occasions with water temperatures between 24.5 °C and 8.4 °C. Dexterity was measured preswim and postswim with a "nut-washer-bolt assembly time test" and cognition with a Stroop test. Core and peripheral body temperatures were continuously monitored. Effects were analyzed by linear mixed-model regression.

Pre-post swim difference in time to complete the nut-bolt assembly increased as water temperatures decreased (1.0 s, 95% CI, 0.5-1.5 per 1 °C, P < .0001; R2 = .456), to a maximum of 14.7 seconds (95% CI, 3.3-26.0). This represented a 47.5% increase in assembly time from 24.5 °C to 8.4 °C, which we consider to be of practical significance. Decreased dexterity was associated with decreased forearm and scapular temperature and decreased cognitive function. Body composition did not affect dexterity, cognitive function, or body temperature during swims. Water temperature did not affect swim speed.

Despite the use of wetsuits, manual dexterity decreased with cold-water swimming. Swimmers, triathletes, and event organizers should consider the implications for safety, performance, and equipment utilization.