Amy L. Moran

Soleus and EDL muscle contractility across the lifespan of female C57BL/6 mice.

All previous aging research on the contractility of rodent skeletal muscle has been conducted on male rodents. Because males and females age differently, we undertook this study to determine if and when age-related decrements in skeletal muscle contractility occur in female mice. Soleus and extensor digitorum longus (EDL) muscles from female C57BL/6 mice aged approximately 4, 8, 16, 24 and 28 mo were assessed in vitro for contractility and subsequently contractile protein content. EDL muscle was resistant to age-related changes in force generation but displayed characteristics of becoming more slow-twitch like. Maximal isometric tetanic force (Po) generated by soleus muscle declined with age. Soleus muscle size and contractile protein contents were not affected by age and thus could not explain the age-related force decrements. Soleus muscle specific Po declined with age being approximately 26% lower in muscles of 16-28 mo-old mice indicating that a deterioration in soleus muscle quality of female mice occurred beginning around the age of ovarian failure. Thus this study provides essential, comprehensive baseline data for future studies on age-related muscle dysfunction in the female mouse.

Estradiol's beneficial effect on murine muscle function is independent of muscle activity

Estradiol (E₂) deficiency decreases muscle strength and wheel running in female mice. It is not known if the muscle weakness results directly from the loss of E₂ or indirectly from mice becoming relatively inactive with presumably diminished muscle activity. The first aim of this study was to determine if cage activities of ovariectomized mice with and without E₂ treatment differ. Ovariectomized mice were 19-46% less active than E₂-replaced mice in terms of ambulation, jumping, and time spent being active (P ≤ 0.033). After E₂-deficient mice were found to have low cage activities, the second aim was to determine if E₂ is beneficial to muscle contractility, independent of physical activities by the mouse or its hindlimb muscles. Adult, female mice were ovariectomized or sham-operated and randomized to receive E₂ or placebo and then subjected to conditions that should maintain physical and muscle activity at a constant low level. After 2 wk of hindlimb suspension or unilateral tibial nerve transection, muscle contractile function was assessed. Soleus muscles of hindlimb-suspended ovariectomized mice generated 31% lower normalized (relative to muscle contractile protein content) maximal isometric force than suspended mice with intact ovaries (P ≤ 0.049). Irrespective of whether the soleus muscle was innervated, muscles from ovariectomized mice generated ∼20% lower absolute and normalized maximal isometric forces, as well as power, than E₂-replaced mice (P ≤ 0.004). In conclusion, E₂ affects muscle force generation, even when muscle activity is equalized.

Effects of Estrogen Replacement on Physical Activity and Body Mass in Aged Mice That Have Experienced Natural Ovarian Failure

2 tests, and ANOVAS. Results : Athletes reported siginficantly greater exercise time (p<.0001) and significantly greater frequency of UI with exercise (p<.0001). There were no significant differences in pelvic floor muscle activity between groups. Conclusions : Although there were no significant differences in pelvic floor muscle activity between athletes and non-athletes, both groups reported greater frequency of UI with greater exercise time. This suggests that pelvic floor muscle activity alone does not predict UI, and that activity related to UI should also be considered. Clinical Relevance : Future studies may focus on the role of increasing pelvic floor muscle activity and endurance to prevent urinary incontinence in these very active women.

Effects of Estrogen Replacement on Voluntary Aerobic Exercise and Body Weight in an Animal Model of Menopause

2 functional activities when compared to women who received no post-operative intervention and adhered to standard care post C-section. Number of Subjects: Eighteen women (n=11 treatment; n=7 control), ages 24 to 35 years old, status post C section were recruited for this study. Those with a history of infection or incision dehiscence, hypertension, diabetes, chronic low back pain or chronic illness were excluded. Participants were randomly assigned to either the treatment or control group. Materials/ Methods: All participants subjective reports of pain and functional abilities were collected in post-operative Week 3, 6 and 8 using the Pain Disability Index, Resumption of Activities of Daily Living Scale, SF 36v2 Survey, a Visual Analog Scale, and Revised Oswestry Disability Index. Objective evaluations of function were performed in conjunction with subjective tests and included rising/sitting down from a chair; stepping up onto different steps; time standing in single leg stance; and lifting up to 20 pounds from floor to knuckle level and knuckle to shoulder level (Week 6 and 8 only). Incision mobility and measurements of rectus diastasis were also performed. Women in the treatment group received treatment 1 time per week for 6 weeks in addition to testing. Women in the control group participated in testing only in Week 3, 6, and 8. Treatment consisted of incision ultrasound and mobilization, abdominal and pelvic floor muscle setting activities, education in proper infant-care body mechanics, and diastasis approximation activities. Statistical analysis included Mann Whitney U, chi square, and paired t tests. Results: Participants in the treatment group demonstrated clinically significant improvement in incision mobility compared to controls (p=.09) with statistically significant change in incision mobility in post-operative Week 3 to Week 8 (p=.001); a reduction in supraumbilical and umbilical diastasis in Week 6 (p=.05) and Week 8 (p=.001); an increase in ability to climb steps without pain by Week 8 (p=.05), and had higher scores on the SF 36v2 in the physical comprehensive summary score (p=.05) compared to controls. Conclusions : The results of this pilot data provides evidence that conservative physical therapy management post C-section reduces pain, incision adhesions, and diastasis while improving physical function in women to a statistically greater degree than standard post C-section care. Clinical Relevance : Physical therapy intervention following C-section may help women recover more rapidly than rest and lifting restrictions alone. Physicians and physical therapists can use this information to make more sound decisions regarding post-operative management of women who have undergone C-section.