This program consisted of 12 group exercise sessions over a three-month period that were offered in Spanish and English. Each two-hour session consisted of 90 minutes of flexibility, cardiovascular, and strength exercises to meet physical activity recommendations and 30 minutes of group discussions that focused on topics related to the adoption and maintenance of physical activity.

Mothers randomized to the HBI group participated in a three-month program where they were given print-based materials (offered in Spanish or English) at each monthly assessment time point. The print-based materials provided information on multiple cardiovascular, strength training, and flexibility exercises that they could do at home.

Mothers were given physical activity goals and coping resources to practice at home and were asked to record their experiences on an activity log. Course content was taught from a detailed training manual and was based on concepts and strategies from social cognitive theory that have been effective in increasing physical activity and fitness levels among mothers. In the first month, mothers attended group exercise sessions twice per week (total of eight group sessions) and exercised on their own once per week. In the second month, mothers attended group exercise sessions once per week (total of four group sessions) and exercised on their own twice per week. In the third month, mothers exercised on their own three times per week.

Self-reported duration of moderate/vigorous physical activity was assessed using the Check and Line Questionnaire (CALQ), with higher numbers representing greater average minutes of moderate/vigorous-intensity PA completed/day over a three-day assessment period. Objective physical activity was assessed using the Fitbit One (2009 version), which is an accelerometer worn on the hip (clipped to a participant's clothing at the waist). For the current study, very active minutes were examined (measure of basal metabolic rate/minute). Activity data was averaged across the three days that the Fitbit was worn, with greater number of very active minutes indicating greater daily moderate/vigorous-intensity physical activity levels.

Cardiorespiratory fitness was assessed via predicted relative maximum oxygen consumption, also known as relative VO2 max (ml/kg/min) after participants completed a timed mile walk, with a greater relative VO2 max being an indicator of greater cardiorespiratory fitness.

Muscle endurance was assessed by the number of modified push-ups completed in correct form, with a greater number of 90° push-ups completed representing greater muscular endurance.

Flexibility was assessed by a modified sit and reach test (in inches) where mothers were instructed to reach forward as far as they could with their hands over each other, over a three-foot ruler, without removing their body from the wall and holding this position for at least two seconds, with greater inches indicating greater flexibility.

Physical Activity Self-efficacy was assessed using the Barriers Self-Efficacy Scale. The 14-item Barriers Self-Efficacy Scale measures a mother's level of confidence in engaging in physical activity despite barriers experienced over the next three months, with higher scores (range=0-100) reflecting higher self-efficacy for physical activity in the face of barriers.