The 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.

The 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.

A 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.

Real 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.

An 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 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.

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 all activity. Average minutes per day of activity within each of the following categories: light = 25.8 mg - 100.5 mg; moderate = 100.6 mg - 428.7 mg; vigorous = > 428.8 mg (mg is the vector magnitude of acceleration calculated in gravities using Euclidean Norm minus 1 metric)

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 all activity. Average minutes per day of activity within each of the following categories: light = 25.8 mg - 100.5 mg; moderate = 100.6 mg - 428.7 mg; vigorous = > 428.8 mg. (mg is the vector magnitude of acceleration calculated in gravities using Euclidean Norm minus 1 metric)

Participants will complete the International Physical Activity Questionnaire (IPAQ) short-form. The IPAQ short-form quantifies physical activity (PA) over the previous week in 2 categories: low, moderate, or high activity; or metabolic equivalents (MET) minutes per week. High PA is categorized as (1)vigorous PA on at least 3 days/week with a combined minimum of at least 1500 MET minutes/week or (2) 7 days of cumulative PA of any intensity that sums to a minimum total of at least 3000 MET minutes/week. Moderate PA is categorized as (1) 3+ days of at least 30 minutes of vigorous PA, (2) 5+ days of moderate PA or walking at least 30 minutes/day, or (3) 5+ days of any level of PA that sums to a minimum of 600 MET minutes/week. Low physical activity is categorized as activity that does not meet the criteria for medium or high activity.

A straight leg raise maximal voluntary contraction (MVC) of each lower extremity will be performed in supine before and within 2 minutes of completing the ASLR fatigue task with a custom made load cell instrumented strength testing device. This device consists of a rigid platform on which the study participant will lie supine. At the foot of the device is a tower that houses 2 load cells and is connected to a lightly padded push plate. This push plate can be raised and lowered such that the participant can push up into the plate (contacts the anterior surface of the participant's shin) or push down onto the push plate (contacts the posterior aspect of the participant's heel). Before the ASLR fatigue task, a minimum of 3 MVC trials will be performed on each leg, with a minimum of 1 minute rest between trials; the highest peak force will be considered the MVC. Only 1 MVC trial per leg will be performed following the fatigue task.

The Active Straight Leg Raise Fatigue Task will be administered. Participants are asked to raise one leg to a heel height of 20 cm while lying supine. Participants are encouraged to keep the leg raised as long as possible. Task failure will be defined as a heel height less than or equal to 10 centimeters off the ground.

An 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) with 5 being the strongest.

Pelvic 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.55 The time in seconds is recorded.

The PFDI-20 is composed of 20 items total on three scales (Pelvic Organ Prolapse, Colorectal-Anal Distress, Urinary Distress), each scored on a 5 point likert scale. Mean scores from each scale are calculated and multiplied by 25, then added together for a total possible range of scores from 0-300. Higher scores indicate increased pelvic floor distress.

Fear of movement (kinesiophobia) will be assessed via the Tampa Scale for Kinesiophobia (TSK). The TSK is a 17-question, self-administered questionnaire that utilizes a 4-point Likert scale (1= strongly agree, 4=strongly disagree). Total scores range from 17-68. A higher score indicates higher levels of kinesiophobia; a score of 17 indicates no/minimal kinesiophobia.

Participants will complete the SF-20 questionnaire, which measures health in six different domains (physical functioning, role functioning, social functioning, mental health, health perceptions, and pain). Scores range from 0-100%, with 0% being the worst score and 100% being the best.

The PSQI assesses seven sleep domains: sleep quality, sleep latency, sleep duration, habitual sleep efficiency, sleep disturbances, use of sleeping medications, and daytime dysfunction. The seven components scores are then added to yield a global PSQI score in the range of zero to 21. Higher scores indicate worse sleep quality. A global score greater than five is diagnostic of poor sleep quality.

Ultrasound imaging will be used to measure the distance between the right and left rectus abdominis at 2 locations above the umbilicus and 2 locations below the umbilicus. IRD will be assessed in supine at rest (end exhalation), while lifting the head, and while lifting one leg.

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.

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.

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.