The Effects of a 16-week Aerobic Exercise and Mindfulness-based Intervention on Chronic Psychosocial Stress: A Nonrandomized Pilot and Feasibility Trial

Intervention Overview This nonrandomized pilot and feasibility trial was conducted as a single-arm trial where all participants were subjected to 16 weeks of aerobic exercise and mindfulness-based training, delivered concurrently. This trial was conducted across two waves: wave 1 (August to November 2016) and wave 2 (April to July 2017). Recruitment was conducted across a one-month time period prior to the trial period of each wave. Pre-test (T0) and post-test (T1) measures were obtained 1 to 4 weeks prior to and after the trial period. As participants were predominantly postgraduate and undergraduate students from a variety of disciplines, these periods were selected to correspond to 'low-stress' periods in the academic calendar (i.e., pre- or -post semester). Participant compliance to the intervention was encouraged in weekly meeting sessions and via weekly email progress reports. Mindfulness-based Intervention (MBI) The MBI was an adaptation of the mindfulness-based Stress Release Program (SRP): a stress management and cognitive therapy program that uses mindfulness practices to raise awareness of the processes underlying stress and negative emotions. The training approach can be summarized in two modules that align with the monitor and acceptance theory (MAT) of mindfulness meditation. This includes: (1) attention monitoring, and (2) acceptance. One instructor who had received direct training from the original facilitators of SRP delivered the intervention. Attention monitoring: The goal of the attention monitoring module was to systematically train participants to improve their ability to observe present-moment experiences through formal meditation practices. The formal practice of meditation involved activities that required sustained focused-attention meditation towards a focus object (i.e., breath, body, sound, or thoughts). The formal practice prescription comprised up to 20 min of focused-attention meditation, daily, over 16 weeks. Completion of this daily target was at the discretion of participants. Formal practice was conducted in a group setting in a seminar room located at Monash University during the weekly training session, and participants were provided with audio recordings containing spoken instructions (Monash University Counselling Services) to guide home practice. To guide progress and track compliance, participants were further instructed to record their formal practice in an online spreadsheet (Google Sheets, Google, US). Formal practice was reported each day as minutes of formal meditation practice. This was converted to hours, and total hours of meditation for each participant across the intervention was recorded as the formal practice dosage. Adherence requirements for the attention monitoring module were completion of at least 50% of the target formal meditation (target = 37.34 h [20 min/day over 16-weeks]; minimum adherence requirement = 18.67 h). Acceptance: The goal of the acceptance module was to foster a mental attitude of acceptance towards negative and stress-laden experiences. This included: (1) a willingness to allow negative experiences to rise and pass, and to let go of thoughts, ideas, or desires that may be associated with the experience (non-attachment), (2) a willingness to be available to negative experiences without attempting to suppress or avoid them (non-avoidance), and (3) a conscious abstention for categorizing an experience as good or bad, or right or wrong (non-judgment). These skills were trained over eight weekly group training sessions and discussion activities (50 min), and homework tasks (completed at discretion of participants) that encouraged participants to reflect on stress-laden or negative experiences with an attitude of acceptance. Adherence requirements for the acceptance module were that participants attend at least 50% of the group psychoeducation sessions, with compliance monitored through attendance records. Aerobic exercise training intervention (AET) The AET program comprised endurance running as part of a half-marathon training program. The AET prescription was three runs per week over 16 weeks (one group session and two self-guided sessions). This included: (1) a 5 min warm up, then an interval run that involved 200 m bursts of near-maximal intensity followed by a 200 m recovery to the total of 16 min, then a 5 min cool down, (2) a short run of moderate or moderate-to-vigorous intensity that gradually increased in duration from 20 min to 60 min over 16 weeks, and (3) a long run at a moderate intensity or moderate-to-vigorous intensity that gradually increased in duration from 20 min to 110 min over 16 weeks. Additionally, participants completed three distance running trials at a moderate or moderate-to-vigorous intensity (Week 6 = 10 km, Week 9 = 10 km, Week 12 = 15 km). Exercise intensity categories were formally defined by the ACSM exercise prescription guidelines: (1) moderate intensity = 46 to less than 64% VO2max, (2) vigorous intensity = 64 to less than 91% VO2max, and (3) near-maximal intensity = greater than or equal to 91% VO2max. Running velocity corresponding to these intensity categories were individually prescribed to each participant by plotting oxygen consumption (VO2 mL/kg/min) against running velocity (km/h) in a regression model derived from a baseline VO2max test. In this way, exercise intensity was completely individualized. In addition to the AET, participants were asked to maintain their regular pattern of physical activity outside of the intervention (e.g., gym, leisure activities, and cycling commutes). To guide performance and track compliance, participants were issued a computerized and GPS-enabled sportswatch (Garmin Forerunner 235, Garmin, US). This device provided participants real-time estimates of running velocity, and therefore of individual exercise intensity. Participants uploaded their running data to an online database weekly, which provided detailed information on training velocity, distance, and time. Adherence requirements for the AET program were completion of at least 50% of all prescribed runs (target = 48 individual runs [3 runs/week over 16 weeks]; minimum adherence requirement = 24 runs). Average % VO2max across all running sessions, total running distance (km), and total running time (h) were also recorded as measures of dosage.