Acute Effects of Exercise in College Students With ADHD

Overview

The overall objective of this study is to examine physical exercise as an intervention for ADHD. The rationale for the proposed study is that physical exercise could serve as an effective treatment for college students with ADHD that has low costs, low risks, and ancillary health benefits and may address the limitations of existing treatments. The central hypothesis is that college students with ADHD will exhibit greater degrees of improvement in executive functioning (i.e., sustained attention, working memory) immediately following sprint interval training (SIT), relative to non-ADHD peers. This hypothesis was formulated based on preliminary studies demonstrating reduced ADHD symptoms and improved executive functioning following physical exercise. Multiple 2 (ADHD vs. control) x 2 (male vs. female) x 2 (exercise vs. none) repeated measures ANOVAs will be conducted to compare students with ADHD (n = 24) to controls (n = 24). The expected outcomes are to confirm this hypothesis and demonstrate the need for further study of physical exercise. If confirmed, the results will provide pilot data for a larger NIH grant proposal aimed at further examining the acute effects of physical exercise (i.e., improved cognitive functioning immediately following exercise) and also the chronic effects of physical exercise (i.e., improved functioning after engaging in regular exercise for an extended period). This outcome is expected to have an important positive impact because physical exercise may serve as an effective treatment for college students with ADHD that is less risky than stimulants, less time-consuming than therapy, and provides ancillary health benefits (i.e., increasing physical fitness, decreasing obesity).

Participant enrollment will consist of forty-eight University of Wyoming (UW) and Laramie County Community College (LCCC) students (24 ADHD group, 24 comparison group) with an even distribution of men and women in each group. Power analyses (G\*Power 3.1) indicated a sample of at least this size is needed to provide 80% power to detect medium effects which have been observed in samples of children with ADHD. Students taking medications that may confound cognitive performance (e.g., antipsychotics, sedatives), are outside the age range (18-25 years), or are at an elevated risk for physical exercise contraindications will be excluded. Prospective ADHD group participants will be recruited through four means. First, students who complete a separate study and endorse five or more inattention (IA) symptoms or report being previously diagnosed with ADHD will be invited for an eligibility assessment. Second, recruitment flyers will be posted on campus. Third, participants will be contacted from previous studies who were diagnosed with ADHD and consented to contact for future research. Fourth, university medical and mental health staff will advertise the study to student clients who have ADHD. Comparison group subjects will be composed of students who complete a separate study, who disavow being diagnosed with ADHD, and endorse three or fewer IA symptoms. As students enroll in the ADHD group, age- and sex-matched comparison subjects will be enrolled. Prior to study enrollment, prospective participants must stratify as being at low risk for physical exercise contraindications using a health history screening questionnaire. Prospective ADHD participants must also meet diagnostic criteria for ADHD on a structured clinical interview. All prospective participants will attend an in-lab appointment to confirm their eligibility, including (a) stratifying as being at low risk for physical exercise contraindications and (b) ADHD prospects meeting diagnostic threshold. After enrolling in the study, participants will be scheduled for two in-lab experimental appointments: sprint interval training (SIT) and Non-SIT. The ordering of experimental appointments will be counterbalanced. This will be done to evaluate possible appointment ordering effects and minimize confounding effects. Both appointments will be scheduled in the mornings, on the same day of the week and at the same time of day. Participants will be asked to wear athletic clothing, as well as abstain from exercise, alcohol, caffeine, and stimulant medication for 12 hours prior to their experimental appointments to minimize the influence they may have on our independent (exercise) and dependent variables (executive functioning). Participants will complete the execute functioning tasks (i.e., Continuous Performance Task or CPT, Digit Span, Letter-Number Sequencing, and Spatial Span or SS) during both the Non-SIT and SIT appointments. They will also be sent a modified mood (i.e., Depression, Anxiety, and Stress Scale or DASS) and ADHD symptoms (Barkley Adult ADHD Rating Scale or BAARS) questionnaire the morning following all experimental appointments. High-intensity SIT was chosen for the proposed study because moderate- to high-intensity aerobic exercises appears to lead to the greatest improvements in cognitive performance among youth with ADHD. The researcher will lead the participant through a set of stretches and 3 minutes of low-intensity cycling on a Schwinn AD2 Airdyne leg-cycling and arm-cranking ergometer to warm up and increase blood flow to active muscles. Participants will then complete 16 minutes of SIT, consisting of eight bouts of 20 seconds of cycling followed by 100 seconds of rest. After each interval, participants will be asked to provide their perceived exertion during the interval, and the researcher will record participant's peak interval heart rate (HR). These measurements are taken to validate that participants exercised at a high intensity. The experimenter will provide encouragement to the participant to work towards ≥85% of their maximum HR. After the eighth and last interval, the participant will rest for 15 minutes before completing the cognitive tasks (i.e., CPT, Digit Span, Letter-Number Sequencing, and SS). Prior to analyses, all variables will be screened. Violations of statistical assumptions will be addressed through data transformations or nonparametric statistics. Relative improvements on objective measurements of EF (i.e., CPT, Digit Span, Letter-Number Sequencing, and SS performance indices) will be examined through 2 (ADHD vs. comparison) x 2 (men vs. women) x 2 (Non-SIT vs. SIT) repeated measures ANOVAs. When interaction effects are significant, paired samples t-tests will be used to evaluate group differences. When interaction effects fail to reach statistical significance, independent samples t-tests will be used to evaluate group differences. The magnitude of omnibus effects for repeated measures ANOVAs will be calculated using partial eta-squared (ηp2). Within-group effects (Cohen's d) and corresponding confidence intervals for within-group effect sizes will be standardized using the variability of non-SIT scores. Between-group effects will be calculated using Hedges g. Values for ηp2 of .01, .06, and .14 will be considered small, medium, and large effects, respectively; corresponding values for d and g are .20, .50, and .80.