This study will compare the impact of traditional group fitness versus a game-based fitness program, designed to maximize enjoyment, on physical fitness.

Fewer than 1 in 10 middle-aged US adults get the recommended amount of aerobic physical activity (PA), greatly increasing their chances of heart disease and stroke. There are over 50 million adults with fitness center memberships, which are used only once per month and, after joining new programs, people quickly stop coming. While many barriers to PA have been cited (e.g., time, cost), the investigators believe that a key, modifiable, and underappreciated barrier is that most adults simply do not enjoy physical activity enough to do it regularly. Studies consistently observe that people who enjoy physical activity more are more likely to be more active in the future. Despite this consistent observation, the investigators are not aware of studies that ask "Would an adult PA program designed to maximize enjoyment increase PA adherence and fitness?". In 2015, our team set out to design an exercise program for adults that maximized enjoyment. Taking inspiration from Pickleball, a popular game of modified tennis, our team created PlayFit. PlayFit is an exercise program in which adults come together three times each week to play a range of sports, all modified to 1) reduce effort (e.g., smaller playing area), 2) reduce injuries (e.g., lightweight low-pressure balls) and 3) reduce competitiveness (e.g., teams chosen randomly, minimize physical contact, no keeping score). Pilot work in the summer of 2016 with 22 adults identified five modified sports that all had Metabolic Equivalent (MET) levels between 5.5 and 6.5 and high satisfaction scores (average of 8.0 out of 10). More importantly, the comments suggest that the investigators have created a social, enjoyable experience: "that was SO much fun", "I've never had so much fun playing soccer". People liked "the laughter during the games", "no pressure, not competitive" and that "it's not about ability, it's just about having fun with people".

In this study, the investigators initially proposed testing whether PlayFit would lead to greater fitness gains, compared to group fitness, to help providers understand in a way that helps providers and fitness center staff understand: "What exercise program should I recommend to promote long-term adherence and fitness?". All subjects were to be expected to exercise three-times weekly for 60 minutes for 12 months. The investigators planned to randomly assign 360 adults to two conditions: 1) Group Fitness activities and 2) PlayFit. The investigators hypothesized that both PlayFit and Group Fitness would increase Maximum Oxygen Uptake (V02max) significantly at 6 months but, after 12 months, mediated by greater enjoyment and higher adherence, participants randomized to PlayFit would have greater fitness and activity gains at 12 months than Group Fitness. The results of this study would have the potential to help patients, providers and fitness center directors by answering the question: "What exercise program should be recommended to sedentary adults in order to promote long-term adherence and fitness?"

Although we originally intended for data collection to conclude by 2021, human-subjects research was largely prohibited throughout 2020 due to the SARS-CoV-2 pandemic. Near the end of 2020 we began to conduct outdoor-only activities. Indoor human-subjects research continued to be restricted throughout 2020 and early 2021.

Once large-scale research restrictions were lifted, recruitment and baseline testing resumed in May 2021, with the first new cohorts beginning in their respective sessions in August 2021. Unfortunately, all human-subjects research was again prohibited for approximately 45 days during January and February 2022. For several reasons, including the likely deconditioning of participants during the pause, that several participants responded that they were unwilling or fearful to return given the perceived health risks, and that some community partners were no longer willing to host the PA sessions during the pandemic, we concluded that our best course of action was to analyze data up to the most recent measurement timepoint preceding this 45-day mandated pause in data collection (month 3).

This decision meant that we were unable to test our original hypotheses. For example, only baseline cardiorespiratory fitness and accelerometry data were available, as the second time point to collect these data was to occur at month 6. However, analyses for group session adherence were possible, as these data were collected continuously throughout the study.

Inclusion Criteria:

• Age 18+
• Sedentary (<90 minutes of self-reported moderate-vigorous activity each week)
• Health care provider must give permission.

Exclusion Criteria:

• History of heart disease, stroke or chest pain.
• Participating in another research study involving physical activity or weight loss.
• Planning to have surgery or move in the next year.

Final, clean, data filed will be uploaded to a publicly available site (e.g., ISPSR), within 12 months of finishing study.

Within 12 months of completing the final follow-up visit on the last study subject.

Adverse event data were collected monthly for the duration of participation in the study, up to 1 year. This time period varied by participant due to the impact of the SARS-CoV-2 pandemic.

Injuries and other adverse events were assessed monthly using a self-report questionnaire that consisted of 7-items focusing on injury location and severity.

Human-subjects research was largely prohibited throughout 2020 and early 2021 due to the SARS-CoV-2 pandemic. Large-scale research restrictions were lifted in May 2021. All human-subjects research was again prohibited during January and February 2022. After that pause, participants were unwilling to return given the perceived health risks and community partners were no longer willing to host the PA sessions during the pandemic. Full participation in the trial as planned was then not possible.

Participants are aware of the two different exercise conditions and accept randomization into either of the two. The investigator and outcomes assessor are masked, but participant is aware of group assignment.