Among the well-known factors that contribute to the development of obesity, childbearing has been reported as an important influential factor. Physical activity is strongly recommended as one of the main tools to reduce any excessive weight gain during pregnancy and also to reduce weight retention in the postpartum period. During the postpartum period, exercise training coupled with a well-balanced nutritional plan, offers an effective intervention to help mothers lose weight safely. International guidelines for physical activity after pregnancy include strengthening routines. Worth noting, most of the above cited studies focused on the benefits of aerobic activities. Strength training interventions are virtually unexplored in postpartum women despite its potential benefits. Compared to the pregnancy period, postpartum barriers to physical activity seem to focus less on health-related barriers. In postpartum, time limitations for childcare become a more common barrier. For this reason, a postpartum exercise program that incorporates the babies in a specific exercise session has a better chance to succeed. The aim of this project is to determine the benefits of strength training in a group class setting in postpartum healthy women with their babies. Whereas mother's participation in regular physical activity may encourage regular physical activity habits in her offspring, a second aim of this project is to also quantify the infant's physical activity. The main measured outcomes are: maternal muscular strength; body composition; aerobic capacity; exercise self efficacy; depressive symptoms; physical activity level and food habits and baby's physical activity level.

Research Questions:

Maternal:

Is a strength training group class (with babies) in postpartum women associated with (I) strength and lean body mass improvement, (II) improvement aerobic capacity, (III) more spontaneous physical activity, (IV) better self efficacy and (V) better mood?

Baby:

Does maternal lifestyle affect the baby's (0-12 months) physical activity level?

Hypothesis:

It is hypothesized that women who complete the 10 week exercise program will have improved strength from pre-intervention to post intervention. It is also hypothesized that women who are adherent to the exercise program will have more active babies.

Methods:

Participants train 60 min per session for 10 weeks on non consecutive days (Tues and Thurs). All training sessions will be supervised by a qualified exercise instructor (graduate in kinesiology) to ensure proper technique and to minimize the risk of injury. Each training session will include a warm up phase of 5 minutes of dynamic and static stretching and a cool down phase consisting of 5 minutes of static stretching. The strength training protocol is based on the American College of Sports Medicine (ACSM) guidelines. Whole-body exercises and different equipment such as weights, elastic bands and balls will be used. Babies will also be included in the exercise routine. Participants will perform 1-3 sets per exercise, 8-12 repetitions per set and a 90-s rest interval between sets. The principle of progressive overload will follow a linear increase as described in ACSM position stand.

All participants will be tested at time points t0 , t1 ( after 5 weeks) and t2 (after 10 weeks; at the and of the study) on: i) strength and body composition; ii) aerobic capacity; iii) objective and subjective physical activity level; vi) exercise self efficacy; v) depressive symptoms and vi) dietary habits.

I. Strength/Body composition assessment At each time point, strength will be assessed for the upper body (push-ups), lower body (squats), and trunk (abdominal curl-up test). The participants will perform push-ups (as many as possible using a fixed pattern of 40 beats per minute - time and number will be recorded up to a maximum of 1 minute). This will be repeated for the number of lower body squat position performed (as many squats as possible using a fixed pattern of 40 beats per minute -time and number will be recorded up to a maximum of 1 minute); these methods have been chosen to reduce the likelihood of any adverse events. The participant will also complete the ACSM-recommended partial curl-up test to assess abdominal strength and endurance. Briefly, as many abdominal curl-ups as possible has to be performed until the participant either stops, or cannot stay in rhythm with a fixed cadence (40 beats/min) up to 1 minute as per ACSM guidelines.

Body composition assessment will include body mass, height, BMI and body fat (sum of five skinfolds: triceps, biceps, subscapular, suprailiac, thigh) measures.

II. Aerobic capacity Briefly, participants perform a 5- min. bout of exercise, stepping up and down from a standard step (height 30 cm) following a specific cadence. During the step test, heart rate (HR) is measured continuously using a heart-rate monitor. Then, VO2max is estimated based on HR and a target exercise intensity (estimated VO2).

III. Physical activity assessment At each time point, participants will to complete two self- reported questionnaires regarding physical activity level, the International Physical Activity Questionnaire (IPAQ; and the Physical Activity Readiness Questionnaire (PAR-Q+).The IPAQ asks participants to recall their levels of physical activity within five domains (leisure, work, transportation, household, recreation) and three intensity categories over a 7-day recall period. The PAR-Q+ determines if it is safe to start an exercise program. Additionally, at t0, t1 and t2 each participant will complete an individual physical activity diary for 7 days. Moreover, during this period participants will continuously wear a pedometer .

IV. Exercise self efficacy Exercise self-efficacy will be measured at each time point (t0,t1 and t2). This survey includes five separate items targeting self-efficacy.

V. Depressive symptoms Levels of postpartum mood will be assessed through the Edinburgh Postnatal Depression Scale (EPDS).

VI. Eating Habits Mother's eating habits will be measured through the Short-Form Frequency Questionnaire (SFFFQ).

VII. Breastfeeding habits will be measured through a Breastfeeding and Infant Feeding Questionnaire.

Baby At each time point, a Rothbart Infant Behavior Questionnaire- Revised (IBQ-R) will be completed by the participants to measure temperament and gross motor activity in infants between the ages of 3 and 12 months.

This study will take place at the Canadian Centre for Activity and Aging gymnasium on Tuesday and Thursday afternoons (time to be determined). Women who contact us will be asked when their baby was born. Those women whose babies are less than 20 weeks of age will be placed in Group A and those women whose babies are older than 20 weeks will be placed in Group B. These groups were divided by baby age because early postpartum women and babies are a different group than those women with babies 6 months and older.

Inclusion Criteria:

• Healthy (free from chronic diseases) women between 8 weeks and 50 weeks after delivery.

Exclusion Criteria:

• Inability to perform strength training or moderate-intensity exercise, athletes/well trained mothers (i.e. mothers undergoing regular strength training), smokers and women who are planning to become pregnant over the subsequent year. Women who cannot read, write and understand English will not be included.

Postpartum women and their infants of both sexes.

De-identified participant data for primary and secondary outcome measures will be made available.

Data will be made available within 1 year of study completion.

Data access requests will be reviewed by an independent review panel. Requestors will be required to sign a data access agreement and privacy statement.