The postpartum period is associated with decreases in physical activity levels, muscular strength, muscular endurance, and pelvic floor muscle function, but little scientific evidence exists on how best to initiate and progress exercise in the postpartum period. This proposal aims to improve habitual physical activity levels, neuromuscular health (i.e., strength, fatigability, symptom burden) and overall wellbeing (i.e., decreased fear of movement, improved sleep quality, improved perception of quality of life) through participation in a weekly exercise program. This study will help to inform postpartum exercise recommendations and is novel as it allows participants to incorporate their children into the exercise routine, thus removing a primary barrier to physical activity/exercise.
18 years of age or older
gave birth in the 24 months prior to study enrollment
less than 6 weeks postpartum or not medically appropriate to engage in exercise regardless of time since childbirth (will be screened using the Get Active Questionnaire for Postpartum)
prescription anti-inflammatory/pain medications that are taken daily;
significant orthopedic conditions that would contraindicate performance of the fatigue task and participation in the exercise intervention (such as fractures, severe scoliosis, etc)
moderate to severe cardiovascular &/or pulmonary disease that contraindicates participation in exercise
Parallel
Progressive exercise
Other interventionA progressive, 8-week exercise intervention has been developed and will be administered in a group setting.
Active Straight Leg Raise Test
Diagnostic testThe ASLR test is a well-established clinical test that assesses stability of the lumbar spine/pelvis, posterior pelvic pain severity, and ability to activate the abdominal muscles. It is performed in supine. Participants are instructed to raise one leg, with the knee straight, to a heel height of 20 cm. The leg is held at the top for 5 seconds, then slowly lowered to the ground. The participant is asked to report perceived difficulty to raise the leg on a 0 to 5 scale (0=not at all difficult; 5=unable to lift leg) and pain on a 0 to 10 scale (0=no pain; 10=worst possible pain). If difficulty or pain are rated at a 1 or higher, the test is repeated with the researcher providing external compression of the pelvis. If perceived difficulty or reported pain are lower with compression, the test is considered positive for lumbopelvic instability. The test is then repeated on the opposite limb.
Active Straight Leg Raise Fatigue Task
Other interventionThe protocol is similar to the ASLR test, except that the participant is instructed to maintain the elevated leg off the ground for as long as possible. A biofeedback air cuff will be placed under the participant's lumbopelvic region to assess movement of the spine/pelvis. The cuff will be inflated to 40 mm Hg, and the participant instructed to keep the needle as close to 40 mm Hg as possible throughout the test; no information will be provided on how to affect cuff pressure, but visual feedback of cuff pressure will be provided throughout the task. Ratings of perceived exertion (RPE) and pain will be obtained from participants every 30-60 seconds. Task failure will be defined as a heel height ≤10 cm or a change in cuff pressure ≥20 mm Hg. Both limbs will be tested, but in different sessions. The order of limb testing (dominant vs non-dominant) will be randomized and counter-balanced. Limb dominance will be self-reported.
Lower Extremity Strength Testing
Other interventionA straight leg raise maximal voluntary contraction (MVC) of each lower extremity an MVC of the hip extensors of the grounded limb will be performed in supine before and within 2 minutes of completing the ASLR fatigue task. The straight leg raise MVC will be performed with a custom-made load cell instrumented strength testing device, which consists of a rigid platform on which the participant will lie. At the foot of the device is a tower that houses 2 load cells connected to a lightly padded push plate. The hip extension MVC will be performed on a force plate. Before the ASLR fatigue task, a minimum of 3 MVC trials will be performed for each muscle group, with a minimum of 1 minute rest between trials; the highest peak force will be considered the MVC. Only 1 MVC trial per muscle group will be performed following the ASLR Fatigue Task.
Ultrasound imaging of abdominal wall
Diagnostic testReal time ultrasound will be used to assess inter-recti distance above and below the umbilicus. Participants will be assessed with B Mode images in supine at rest, in supine while lifting their head, and in supine while performing a straight leg raise. The Principle Investigator has training and experience in musculoskeletal ultrasound.
Pelvic Floor Muscle Strength Testing
Other interventionAn internal vaginal pelvic floor muscle assessment will be performed at baseline and study completion by a licensed physical therapist with advanced training in pelvic floor muscle examination and treatment. Pelvic floor muscle function will be assessed using the PERFECT scale, which assesses both muscular strength ("P" for "power") and endurance ("E"). Strength is assessed by cueing the participant to perform a maximal voluntary pelvic floor muscle contraction while the examiner has their index finger inserted into the vagina. The modified Oxford scale is used to grade strength on a scale of zero (0) to five (5).
Pelvic Floor Muscle Endurance Testing
Other interventionPelvic floor muscle endurance is also assessed via the internal vaginal PFM examination. After strength testing is performed, participants are instructed to perform a maximal PFM contraction and hold for as long as possible (maximum of 10 seconds). The examiner counts the length of the contraction, and timing is stopped either when (1) strength of the contraction declines or (2) the maximum of 10 seconds is reached. The time in seconds is recorded.
Average Total Activity Counts (TAC) per day over 7 days
Physical activity habits around the time of testing will be assessed with a tri-axial accelerometer for 7 days outside of the laboratory, in part by measuring the TAC per day. TAC is the total number of filtered, full-wave rectified, integrated accelerations (all directions). These will then be averaged/day based on the total number of valid wear days for each participant.
Physical Activity Measured by Average Steps per day over 7 days
Physical activity habits around the time of testing will be assessed with a tri-axial accelerometer for 7 days outside of the laboratory, in part by measuring mean steps per day. This will be quantified as reported by the Ametris (formerly ActiGraph) accelerometer and CentrePoint analysis software. The Algorithm used by Ametris is not publicly available, but Ametris/ActiGraph accelerometers are frequently used in research quantifying physical activity.
Mean Duration per day of Moderate-Vigorous Physical Activity (MVPA) over 7 days: tri-axial counts
Physical activity habits around the time of testing will be assessed with a tri-axial accelerometer for 7 days outside of the laboratory, in part by measuring mean duration per day of MVPA. Intensity of physical activity assessed using tri-axial counts (per the accelerometer software) are as follows: Light physical activity is between 200 and 2690 counts/min, moderate intensity between 2690-6166 counts/min, and vigorous intensity is ≥ 6167 counts/min. MVPA is ≥2690.
Mean Duration per day of Moderate-Vigorous Physical Activity (MVPA) over 7 days: vertical counts
Physical activity habits around the time of testing will be assessed with a tri-axial accelerometer for 7 days outside of the laboratory, in part by measuring mean duration per day of MVPA. Intensity of physical activity assessed using vertical counts (per the accelerometer software) are as follows: Light physical activity is between 100 and 759 counts/min, moderate intensity is 760-5999 counts/min, and vigorous intensity is ≥ 6000 counts/min (MVPA is \> 760 counts/min).
Assessment of fatigability of the lumbopelvic stabilizing muscles measured by the ASLR Fatigue Task: Mean Pain Score
For the ASLR Fatigue Task, the participant is instructed to maintain the elevated leg off the ground for as long as possible. A biofeedback air cuff placed under the participant's lumbopelvic region assesses movement of the spine/pelvis during the test. The cuff will be inflated to 40 mm Hg, and the participant will be instructed to keep the needle as close to 40 mm Hg as possible throughout the test. Pain Scores will be measured (0-10 with higher scores increased pan) every 30-60 seconds. Task failure will be defined as a heel height ≤10 cm or a change in cuff pressure ≥20 mm Hg.
Percent Change in Global Surface EMG Recordings: Abdominal Muscles
Electromyography (EMG) will be reported as the root mean square (RMS) value. The percent change in EMG from the start of the ASLR Fatigue task to task failure will be examined.
Percent Change in Global Surface EMG Recordings: Rectus femoris
EMG for the rectus femoris will be normalized to the maximum RMS EMG obtained during lower extremity strength testing. The percent change in EMG from the start of the task to task failure will be examined.
Root mean square (RMS) of global EMG
Muscle behavior will be quantified from surface EMG recordings of the rectus abdominis and rectus femoris using multi-channel array surface EMG electrodes during maximal and submaximal contractions and fatiguing exercise of the abdominal muscles. If successful, RMS of global EMG will be reported.
Percent of Maximum Voluntary Isometric Contraction (MVIC)
Muscle activity will be quantified from surface EMG recordings of the rectus abdominis and rectus femoris using a multi-channel array surface EMG electrodes during submaximal contractions and fatiguing exercise of the abdominal muscles, and normalized to the RMS EMG during maximal voluntary isometric contractions (MVIC). If successful, percent of MVIC will be reported.
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