Women in Cardiac Rehabilitation: Optimizing the Training Response

Cardiovascular disease (CVD) is the foremost leading cause of death in women.1 More than 1 in
3 female adults are affected by CVD.2 Though the prevalence of CVD in women remains high,
there is a relative paucity of research pertaining to women in Cardiac Rehabilitation (CR).
Improvements in peak VO2 in CR are prognostically important 3-5 and several studies have
shown that women increase their aerobic capacity in CR to a lesser degree than men.6,7 Even
as women participate in many traditional CR programs, data specificity and subsequent
research has yet to emerge in a meaningful way so that women-centered CR can be better
customized and their outcomes properly assessed.

It is understood that women demonstrate a lower VO2 max than that of men8 on entry into CR
which is often attributed to their smaller muscle mass, lower hemoglobin and blood volume,
and smaller stroke volume relative to men.9 A finding of our previous study on aerobic
capacity in patients entering cardiac rehabilitation revealed that values of peak VO2 on
entry to CR were extremely low, particularly in women.6 It has been observed in the CR
setting that women have lower physical function scores than men.10 Handgrip strength also
differs between men and women.11 Baseline maximal exercise capacity of peak VO2 has been
found to be the best predictors of baseline physical function score along with strength
measures of leg press and bench press.10 Another study of ours revealed that while a peak VO2
below 15 was associated with high risk of annual all-cause mortality among men, a peak VO2
below 12 was associated with highest risk among women.12 Though women in another study had
lower peak exercise capacities than men, they achieved similar relative improvements as a
result of cardiac rehabilitation.13 Research in the field deserves further exploration as the
results remain mixed. As women improve less than men in attaining peak VO2, we have put
together a training program for women with a goal of optimizing their training potential in
CR. This program combines the utilization of a training technique termed interval training
along with specific strength training exercises of the legs. Previous studies that included
both men and women with CAD have indicated that high intensity interval training might be
more beneficial than moderate or standard intensity training in terms of improvements in
aerobic fitness.14-16 However, the specificity of benefits for women remains rather elusive.
Thus, studying variations in strength and power with appropriate interval training could help
us attain better outcomes.

We hypothesize that women, irrespective of age, would be capable of high intensity interval
training to improve peak aerobic capacity in the CR setting. Furthermore, since women often
have a deficit of thigh strength entering CR, strength training will also be included. The
purpose of this study is to examine the value of high intensity interval training and
strength training to maximize aerobic fitness in Cardiac Rehabilitation for women. This may
contribute to establishing specific protocols and training guidelines for future program
design for women in CR. Since a set of comprehensive CR guidelines pertaining to women is
lacking, it is hoped that the results of this study will help us develop exercise protocols
and regimen to better structure and modulate CR programs for optimal benefit to women.

Study Design: Describe the research design, including a description of any new methodology
and its advantage over existing methodologies.

This is a prospective study to be conducted at University of Vermont Cardiac Rehabilitation
Center involving female cardiac patients. At entry to CR, data to be collected from patients
participating in the study include: 1) Baseline characteristics such as age, body weight and
height for calculation of BMI, systolic and diastolic blood pressure (rest), heart rate
(rest, peak), medications, prior cardiac event etc., 2) Aerobic fitness assessment using a
symptom-limited graded exercise tolerance test on treadmill to determine Peak metabolic
equivalents (METs peak) and Peak VO2, 3) Strength measurement assessment using a
single-repetition maximal lift (bench press for upper body and leg extension for lower body)
and a handgrip dynamometer for handgrip strength, 4) Perceived exertion rate after each
training session using BORG 6-20 scale18, 5) Self-reported physical functioning assessment
using the Medical Outcomes Study Short Form-36 (MOS SF-36) survey questionnaire (0-100 scale)
with 100 representing excellent physical functioning, 6) a co-morbidity score to determine
the presence of peripheral vascular disease, cerebrovascular disease, chronic lung disease,
or orthopedic limitations. If a co-morbid condition is present, it is quantified by severity
as follows: 1, present but not exercising-limiting; 2, present and impacts on exercise
performance; and 3, exercising-limiting; a total co-morbidity score ranging from 0 to 12 is
to be determined for each participant, and 7) any "quality of life improvements" for
participants as measured by the MacNew Heart Disease Health-Related Quality of Life
Questionnaire.19 All of these measures with the exception of the MacNew questionnaire are
collected on all CR entrants in the clinical setting.

The standard exercise training protocol will comprise of 3-one hour long sessions per week
spanning 12 weeks, consisting of aerobic exercise and resistance training. Each session
includes treadmill walking, rowing, cycling and aerobic exercise in the control group will be
performed at an intensity of 70-85% of peak HR (moderate intensity) for a total of 45 minutes
with rest periods as needed between equipment Patients will also participate in resistance
training which will include 1 set of 10 repetitions at an intensity of 60-65% of the single
repetition maximal lift (1-RM) of the following: leg extension, leg curl, bench press,
shoulder press, lateral pull down, and bicep curl. For those who underwent CABG, upper body
resistance training will take place 3 months post-operatively.

The high intensity interval training with more intensive strength training will consist of
3-one hour sessions over the course of 12 weeks. For this group, all aerobic training will
comprise of "high intensity interval treadmill walking" (HIT). Patients will warm up for 5
minutes at 60-70% of peak HR followed by 4 minute intervals to achieve 90-95% of peak HR. In
between each interval will be a 4 minute walking period at 50-60% of peak HR. You will also
perform other types of exercise such as cycling and rowing for up to a total of 45 minutes of
aerobic exercise. You can rest, as needed, in between different types of exercise equipment.
Additionally, this group will undergo strength training as described above, however, they
will do 2 sets of 10 repetitions for upper leg exercises at an intensity of 80% 1-RM.

At entry to CR, the study participants will be asked to fill out the following
questionnaires:

1. Medical Outcomes Study Short Form-36 (MOS SF-36) survey questionnaire to report the
physical functioning

2. MacNew Heart Disease Health-Related Quality of Life Questionnaire to measure quality of
life improvement

At the completion of the study after 12 weeks, the participants will be asked to do the same
measures. Random IDs will be given to patients filling out the survey instruments to maintain
privacy and confidentiality. Additionally, the results will be stored on a password-protected
secure computer network of UVMMC.

Statistical Considerations:

Power calculations undertaken by us (80% power with 5% level of significance) based on
Wisloff study15 suggested that a sample size of 19 per group is needed to detect a difference
of 30% between groups in Peak VO2 by exercise training regimen. We intend to conduct an
interim updated power analysis once we have 10 patients to better fine tune the power
analysis.

Baseline characteristics will be presented as mean SD. Non- paired t-tests will be used for
comparison between groups at baseline (pre-test), at the conclusion of the study (post-test),
and percent changes after exercise regimen. ANOVA for repeated measures will be used for
analyzing the effect of the exercise regimen between groups. A level of significance of
P<0.05 will be used to indicate statistical significance.

All eligible participants in the study will perform the CR exercise training under the
supervision of exercised physiologists. This study presents minimal risk to participants as
indeed, CR participation yields a 25% decrease in overall mortality and a 31% decrease in
hospitalizations in year 1.20

Benefits of CR include improved overall cardiovascular health, knowledge of physical
functioning opportunities and limitations, and ability to both undertake and continue
exercise for a longer span of time beyond the end of the study. An underlying assumption of
the study is optimization of exercise might yield a greater training increase in Peak VO2 in
the HIT group along with possible greater improvements in fitness and quality of life.

Both groups will obtain all of the standard benefits of CR which include a lower mortality
rate, a lower re-hospitalization rate, and an improved quality of life.

Data Safety and Monitoring:

Hard copy of paper data will be stored in locked office and file cabinets. All electronic
data will be password protected and stored on the UVMMC secured network server.

Inclusion Criteria: Heart disease, eligible for cardiac rehabilitation -

Exclusion Criteria: Peak VO2 < 12 ml/kg/min