Impact of Heat on Dual Task Performance

Participants will perform single and dual tasks at baseline (normal temperature). These tasks are cognitive (recall and serial subtraction) and motor (gait and balance). Then participants will put on firefighter gear and walk on the treadmill in a hot, humid environment until their core temperature reaches 39C. Then, they will repeat the single and dual tasks with the elevated core temperature.

• heat stress (Other): participants will walk in a heat chamber to increase core temperature

Primary outcomes

• expanded timed up and go [baseline and post-heat stress, both day 1]: A timed test where participants stand from a chair, walk 10 m, turn, and return to the chair. Longer times indicate slower gait speed
• Firefighter balance test [baseline and post-heat stress, both day 1]: A timed test where participants walk an obstacle course measuring dynamic balance, having to step up/down, walk a narrow path, and duck under an obstacle. Longer times indicate worse dynamic balance.
• Backward Digit Recall [baseline and post-heat stress, both day 1]: A timed test where participants recall a series of numbers in reverse order. More digits indicate better recall.
• Serial Sevens Subtraction [baseline and post-heat stress, both day 1]: A timed test where participants count backwards from a starting value by 7s, with the more correct responses in 20 seconds indicating better cognitive ability for this task.
• Serial Sevens Subtraction-Expanded Timed Up and Go Dual Task [baseline and post-heat stress, both day 1]: Performance of serial sevens subtractions while performing the Expanded timed up and go test (ETUG). This test is timed (ETUG) and correct responses tabulated (subtraction).
• Serial Sevens Subtraction-Firefighter Balance Test Dual Task [baseline and post-heat stress, both day 1]: Performance of serial sevens subtractions while performing the Firefighter Balance Test (FFBT). This test is timed (FFBT) and correct responses tabulated (subtraction).
• Backward Digit Recall-Expanded Timed Up and Go Dual Task [baseline and post-heat stress, both day 1]: Performance of backward digit recall while performing the Expanded timed up and go test (ETUG). This test is timed (ETUG) and correct responses tabulated (Recall).
• Backward Digit Recall-Firefighter Balance Test Dual Task [baseline and post-heat stress, both day 1]: Performance of backward digit recall while performing the Firefighter Balance Test (FFBT). This test is timed (FFBT) and correct responses tabulated (Recall).

Sex: All, ages: 18 Years to 57 Years, accepts healthy volunteers

Inclusion Criteria:

* health via PARQ+

Exclusion Criteria:

* inability to safely swallow core temperature pill
* musculoskeletal injury in past 3 months
* diagnosed concussion or vestibular disorder
* known pregnancy

• Cheung SS, McLellan TM, Tenaglia S. The thermophysiology of uncompensable heat stress. Physiological manipulations and individual characteristics. Sports Med. 2000 May;29(5):329-59. doi: 10.2165/00007256-200029050-00004. PMID 10840867
• Moreira PED, Dieguez GTO, Bredt SDGT, Praca GM. The Acute and Chronic Effects of Dual-Task on the Motor and Cognitive Performances in Athletes: A Systematic Review. Int J Environ Res Public Health. 2021 Feb 10;18(4):1732. doi: 10.3390/ijerph18041732. PMID 33579018
• Ness BM, Zimney K, Schweinle WE, Cleland JA. DUAL-TASK ASSESSMENT IMPLICATIONS FOR ANTERIOR CRUCIATE LIGAMENT INJURY: A SYSTEMATIC REVIEW. Int J Sports Phys Ther. 2020 Dec;15(6):840-855. doi: 10.26603/ijspt20200840. PMID 33344002
• Ball D. Contrasting effects of heat stress on neuromuscular performance. Exp Physiol. 2021 Dec;106(12):2328-2334. doi: 10.1113/EP088191. Epub 2020 Jul 15. PMID 32608071
• Doohan MA, Watzek JT, King N, White MJ, Stewart IB. Does increased core temperature alter cognitive performance during exercise-induced heat strain? A narrative review. J Appl Physiol (1985). 2023 Jul 1;135(1):35-52. doi: 10.1152/japplphysiol.00070.2023. Epub 2023 May 4. PMID 37141422
• Donnan K, Williams EL, Morris JL, Stanger N. The effects of exercise at different temperatures on cognitive function: A systematic review. Psychol Sport and Exerc. 2021;54.

• Erin McCallister, Study director, Louisiana State University Health Sciences Center Shreveport