Aerobic and resistance training exercises have been shown in many studies to improve cardiovascular and respiratory health. Exercise helps lower blood pressure, reduce resting heart rates, lower cholesterol levels and improve arterial flexibility.
Regular exercise also helps improve a cardiovascular diagnostic measure known as heart rate variability (HRV). In simple terms, HRV is the amount of time that transpires between heartbeats and is usually evaluated in milliseconds. In general, if there is a large gap in time between heartbeats, one’s HRV is considered to be good. On the flip side, if there is a short gap in time between heartbeats, a person’s HRV is considered bad.
When physicians evaluate a patient’s HRV, they are most interested in seeing whether the heartbeats are getting closer together or farther apart when measured over time. When they are getting closer together, physicians become concerned as this indicates the heart is working harder than it did before. Poor HRV (meaning shorter and shorter gaps of time between heartbeats) is a significant predictor of cardiovascular events such as heart attacks and strokes.
During exercise, heartbeats increase in frequency and occur in shorter time spans as the heart responds to increased demands from muscles and other tissues in the body to provide a heightened supply of oxygen. After exercise, the heart rate slows down over time and eventually settles back to a normalized level known as a person’s “resting heart rate.” The ultimate HRV goal in improving cardiovascular health is to lengthen the resting activity of the heart, which also leads to lower resting heart rates.
One such exercise technique you might not think of as providing a heart health benefit is flexibility training, i.e., stretching. To wit, a study published online ahead of print in the Journal of Strength and Conditioning Research demonstrated how a simple 10-minute, three-stretch program significantly improved HRV and resting heart rate in 10 males with limited flexibility.
In fact, the mean post-stretching improvement in one of the HRV measures evaluated in the study achieved from a single 10-minute stretching session was 16% compared to the study subjects’ mean pre-stretching HRV. Mean resting heart rate recorded 30 minutes after the 10-minute stretching session decreased by 12% compared to the pre-flexibility training levels. Those are pretty significant improvements from a single 10-minute stretching session!
The study authors described the stretching program used in the research project as follows:
“The stretching protocol was performed according the static method in the following exercises:
(a) trunk flexion with the right knee extended and the left lower limb relaxed in semiflexion;
(b) trunk flexion with the left knee extended and the right lower limb relaxed in semiflexion;
(c) trunk flexion with the feet united, hips abducted, and knees flexed — butterfly position.
The session consisted of 3 stretches for 30 seconds at the maximum range of motion with a 30-second rest between sets and 1-minute rest between exercises. Each training session lasted approximately 10 minutes, and the HR was recorded continuously. All subjects performed the same exercises, and the HR was recorded during 30 minutes at rest in the supine position, along the whole stretching session and throughout 30-minutes post exercise recovery also in the supine position.”
It should be noted that the average age of the study subjects was 23, and that they acknowledged exercising three to five times a week for at least one year prior to the study. They were selected for the study because they were considered to have limited flexibility as determined by a diagnostic test known as the “sit and reach” test in which a person sits with feet extended in front and then tries to extend their hands as far forward as possible to reach the toes or beyond. People with distances below 28 cm are considered to have poor flexibility, and the mean distance exhibited by the 10 study subjects was 23 cm.
Stretch It Out
Now, the research study does not address how long after a single stretching session HRV and heart rate improvements persist, and the study authors do not speculate as to whether the improvements can be sustained through an ongoing, regular stretching program. All the same, the benefits of a simple stretching program likely confer to people of all ages regardless of current flexibility or exercise frequency in our opinion.
For example, if you exercise regularly but don’t include a modest stretching program at the end of your workout, this study offers another reason to do so beyond relieving muscle soreness and joint stiffness. In addition, if you happen to miss a workout on a given day (too busy, traveling, other commitments), stretching for 10-20 minutes before you go to bed at night will not only help you relax and aid your ability to fall asleep, but this study suggests that a single stretching session can also deliver short-term cardiovascular benefits.
Conversely, if you are not currently engaged in a regular aerobic and/or resistance training exercise program but desire to improve your cardiovascular health, adding a daily 10-20-minute stretching program may not only help wake up your muscles and joints to the prospect of regular exercise, but could also offer you a short-term protective cardiovascular benefit.
Supporting these points, the study authors concluded, “The present results suggest that stretching routines may contribute to a favorable autonomic activity change in untrained subjects. Because sedentary persons have higher potential risk for the later development of cardiovascular disease, they could therefore benefit from the cardiovascular protection effect of flexibility training on the parasympathetic activity (our insert: parasympathetic activity in this context means the energy demands placed on the heart).”
 Farinatti PTV, et al. Acute Effects of Stretching Exercise On The Heart Rate Variability In Subjects With Low Flexibility Levels. Journal of Strength and Conditioning Research. 2011 March 3 [Epub ahead of print].