Military performance depends on high level cognition specifically, executive function (EF) while simultaneously performing strenuous exercise. However, most studies examine cognitive performance following, not during, exercise. Therefore, our aim was to examine the relationship between EF and exercise intensity. Following familiarization, thirteen Reserve Officer Training Corp cadets (19.6 ± 2 yrs, 5 women) completed a graded exercise test (GxT) and two EF exercise tests (EFET) separated by ≥ 24hrs. EFET was a combined iPad-based EF test (Cedar Operator Workload Assessment Tool) and GxT. Heart rate (HR) and Prefrontal cortex (PFC) oxygenation (Near infrared spectroscopy, NIRS) were continuously recorded. The EF score was analyzed for accuracy of responses (%Hit Rate). Heart Rate Reserve was calculated to normalize exercise intensity (%HRR). PFC oxygenation utilized NIRS variables to calculate Tissue Saturation Index (%TSI). Data from EFET trials were averaged into a singular response. % Hit Rate declined at HRRs ≥ 80%, reaching nadir at 100% HRR (74.09 ± 10.63 %, p < 0.01). TSI followed a similar pattern, declining at ≥ 70% HRR and at a greater rate during EFET compared to GxT (p < 0.01), reaching a nadir in both conditions at 100% HRR (60.39 ± 2.94 vs. 63.13 ± 3.16 %, p < 0.01). Therefore, EF decline is dependent on exercise intensity, as is % TSI. These data suggest reductions in EF during high intensity exercise are at least in part related to attenuated PFC oxygenation. Thus, interventions that improve PFC oxygenation may improve combined exercise and EF performance.

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Military performance often depends on high level cognition specifically, executive function (EF) while simultaneously performing strenuous exercise. Studies of EF during exercise have provided varied results (enhanced vs diminished function). Similarly, cognitive change models suggest that changes in EF (positive or negative) during exercise stem from a reallocation of substrates (e.g. blood flow, O2) from the prefrontal cortex (PFC). PFC oxygenation increases during low and decreases at high exercise intensities. Thus, understanding PFC oxygenation responses during concurrent EF and exercise provides insight into EF and exercise performance which is applicable to the military. Purpose To determine PFC oxygenation and EF performance over a range of exercise intensities. Methods 15 Reserve Officer Training Corp (ROTC) cadets (19.6 ± 2 yrs, 5 women) completed 4 visits separated by ≥24hrs. Visit 1) familiarization trial 2) treadmill maximal graded exercise test (GxT): 3.5 mph, 0% grade increasing 2% every 2‐min until 16%, at which speed increased by 0.5 mph every 2‐min until exhaustion. Visits 3) & 4) Executive function and exercise test (EFET, data from visits 3 & 4 average into a singular response). EFET was combined comprehensive iPad based EF test (Cedar Operator Workload Assessment Tool, fixed to the treadmill) and GxT. Heart rate (HR), respiration rate (RR), arterial blood saturation (SpO2) (Equivital Life monitoring system) and PFC oxygenation (Near infrared spectroscopy, NIRS) were continuously recorded. The EF score for each intensity was analyzed for accuracy of correct responses and termed % Hit Rate = correct responses, (correct responses+ false positives + incorrect response). Heart Rate Reserve was calculated to normalize exercise intensity (%HRR). NIRS variables, oxygenated hemoglobin (O2Hb), deoxyhemoglobin (HHb), and total hemoglobin (tHb) were used to calculate Tissue Saturation Index (TSI). Results Data are mean ± SD, effect size Ω2. During the EFET, % Hit Rate was unchanged from baseline until 70% HRR (99.0 ± 7.0 vs 85.0 ± 6.0 %, p < 0.01) where it steadily declined with intensity to a nadir at 100% HRR (51± 20 %, p < 0.01). TSI followed a similar pattern to Hit Rate, only declining ≥70%HRR and did so at a greater rate during EFET compared to GxT (p<0.05, Ω2=0.02), reaching a nadir in both conditions at 100% HRR (59.3 ± 2.0 vs. 61.7 ± 3.5 %, p<0.05). Other variables, RR, SpO2, and HR did not differ in response in the EFET compared to GxT (p>0.05). Conclusion EF is only affected during high intensity exercise (above 70%HRR), where it declines linearly to maximal exercise. This is mirrored by PFC oxygenation, declining 3 70%HRR and to a greater extent than just exercise alone (vs GxT) at very high intensity. Systemic variables are not different between GxT and EFET. Therefore, EF decline is dependent on exercise intensity, as is TSI. These data suggest reductions in EF during high intensity exercise are at least in part related to attenuated PFC oxygenation.

Introduction Both sport and tactical performance relies on one’s ability to complete high levels of physical exercise simultaneously engaging in complex cognitive tasks (e.g. executive function). Several studies have found that combined cognitive tasks and muscle contractions can induce an earlier onset of fatigue and impair performance. However, it remains unclear if cognitive stress attenuates whole body dynamic exercise performance. Purpose To determine if the addition of a cognitive task would limit maximal whole‐body exercise performance. Methods 16 healthy Reserve Officer Training Corp cadets (19.6 ± 2 yrs, 5 Female) completed 3 graded exercise tests (GxT) separated by ≥ 24 hrs. The first GxT began at 3.5 mph, 0% grade increasing 2% every 2‐min until 16%, where speed increased by 0.5 mph every 2‐min until volitional fatigue. The next two GxTs (EFET, executive function exercise test) were identical to the first GxT while simultaneously completing an executive function test (Cedar Operator Workload Assessment Tool) on an iPad fixed to the treadmill. Heart rate (HR), respiration rate (RR), arterial blood saturation (SpO2) (Equivital Life monitoring system) and cerebral oxygenation (calculated tissue saturation index, TSI) using Near infrared spectroscopy was recorded throughout each test. Performance was determined by the number of stages completed. All data during the two EFET tests were averaged to form a singular response. Results Data are mean ± SD, effect size calculated as Ω2. Concurrent executive function test and exercise did not significantly affect the number of stages completed when compared to the GxT (Stages completed, GxT= 8.6 ± 1.3, EFET= 8.5± 1.2, p= 0.2). However, 5 of 16 subjects completed fewer stages during EFET compared to GxT (Stages completed, GxT= 9.2± 1.3, EFET= 8.5± 1.1, p<0.01) were labelled Non‐Resilient (NR). The other 11 subjects who completed the same or more stages during the EFET were labeled Resilient (R) (Stages completed, GxT= 8.4± 1.3, EFET= 8.5± 1.2, p= 0.10). The R group had similar TSI responses between trials (p= 0.3, Ω2 = 0.01) while the NR group had a greater decay in TSI at the highest intensities during EFET compared to GxT (p<0.01, Ω2 = 0.11). Post hoc was unable to identify disparities at specific intensities (90% 61.9± 1.7 vs 63.7± 1.3 d=1.2 p>0.05, 100% 59.9± 1.7 vs 62.1± 1.3 d= 1.4 p>0.05, EFET vs. GxT, respectively). No difference in HR during EFET trials compared to GxT for NR (p=0.9, Ω2= 0.02) or R (p=0.5, Ω2 = 0.06) groups. No other variables differed between trials and groups. Conclusion Concurrent cognitive task does not impact graded exercise performance. However, our data suggests inter‐individual responses exist, where that some individuals maintain performance, while others cannot. The large effect size indicates NR were unable to sustain TSI during EFET. Therefore, maintenance of exercise performance with cognitive task seems to be related to one’s ability to preserve brain oxygenation during high intensity exercise.