MEASURING HEART RATE AND BLOOD PRESSURE DURING STRENGTH TRAINING PROGRAMS
Blood pressure is difficult to measure in regular exercise situations, but heart rate monitors can give a useful rep-by-rep estimation of BP.
While it is generally known that heart rate response to endurance exercise is an important indicator of cardiovascular effort and a guide for training intensity, many fitness professionals aren’t aware of the immediate cardiovascular response to strength training.
Generally, adults are advised to perform aerobic exercise at approximately 75 percent of their maximum heart rate. Training at this intensity typically results in a peak systolic blood pressure increase of about 35 percent. But in studies conducted with middle-aged adults, peak systolic blood pressure increases of approximately 35 percent were also found during 10 repetition maximum efforts in arm strength exercises, and 50 percent increases were found during leg strength exercises, in other words, the systolic blood pressure response to standard strength training is similar to that of endurance exercises, and well within acceptable limits for physical activity.
While this is good news for strength-training participants and personal trainers, it is not practical to monitor a client’s blood pressure during an exercise set. Fortunately, the increase in systolic blood pressure is paralleled by a similar increase in heart rate on a repetition by repetition basis. So, by wearing a heart rate monitor, heart rate can be constantly viewed and the training program can be altered accordingly. For many populations, such as cardiac rehab patients, post-surgery participants and elderly exercisers, monitoring heart rates during strength exercise simply makes good sense.
Heart rate research
A study conducted on the heart rate response to various strength exercises and training intensities found that strength training performed in a sensible manner appears to produce cardiovascular responses similar to standard aerobic exercise.4 The strength exercises examined were machine chest presses and machine bicep curls for the upper body muscles, and machine leg extensions and machine leg curls for the lower body muscles. The training intensities assessed were at 70 percent and 85 percent of maximum resistance (70 percent and 85 percent of 1 RM).
All of the research subjects wore new electronic heart rate monitors while they performed as many repetitions as possible with both 70 percent and 85 percent of their 1 RM in the four strength exercises. And, the subjects recovered as long as necessary to return to their resting heart rates between successive trials.
Study results
Results of the study were somewhat surprising. Exercising to the point of muscle fatigue with 70 percent and 85 percent of maximum resistance produced almost identical increases in heart rate. On average, the 70 percent of 1 RM weight-load increased subjects’ heart rates to 123 beats per minute, and the 85 percent of 1 RM weight-load increased their heart rates to 122 beats per minute. As shown in Figure 4, the peak strength-training heart rates reached 69 percent and 68 percent of the maximum predicted heart rate, respectively.
It is interesting to note that both of these peak strength-training heart rates were lower than what is typically recommended for aerobic exercise (approximately 75 percent of maximum predicted heart rate). This finding indicates that properly performed strength training and standard aerobic exercises can produce similar heart rate responses.
The increase in heart rate above resting level was 53 beats per minute when exercising with 70 percent of 1 RM weight-load, and 50 beats per minute when training with 85 percent of 1 RM weight-load.
On average, the subjects completed about 13 repetitions at 70 percent of 1 RM, and about 7 repetitions at 85 percent of 1 RM. That is, when training with the lighter weight-loads, the participants’ heart rates increased about 4 beats per repetition (53 beats divided by 13 reps), and when training with the heavier weight-loads, their heart rates increased about 7 beats per repetition (50 beats divided by 7 reps). Figure 5 illustrates these response relationships graphically.
Although both exercise weight-loads seem to be safe from a cardiovascular perspective, training with 70 percent of 1 RM is recommended for cardiac rehabilitation patients, frail elderly participants and other at-risk populations, as the heart rate increase is less on a repetition by repetition basis.5 Also, if a physician requires a lower peak heart rate, the exerciser may simply perform fewer repetitions with the 70 percent of 1 RM weight-load. As indicated in Figure 1, performing 11, nine or seven repetitions at 70 percent of 1 RM would raise the heart rate approximately 44, 36 or 28 beats above resting, respectively. This training resistance should still be sufficient to stimulate strength gains, even though the exercise set is terminated prior to experiencing muscle fatigue.
Summary
Strength training performed in a sensible manner (slow movement speed, full movement range, strict exercise form) appears to produce cardiovascular responses similar to standard aerobic exercise. In this study, the peak systolic blood pressure response was approximately 35 percent above resting level during aerobic exercise that was performed at 75 percent of maximum predicted heart rate. The peak systolic blood pressure response during upper-body and lower-body strength exercises with the 10-repetition maximum weight-load was about 35 percent and 50 percent above resting level, respectively.
The heart rate increases in a similar manner to systolic blood pressure during strength exercise, and is considerably easier to monitor. Peak heart rates attained when training to fatigue with both 70 and 85 percent of maximum weight-load averaged about 70 percent of maximum predicted heart rate. Heart rate increased approximately 7 beats per repetition with 85 percent of the 1 RM resistance, but only 4 beats per repetition with 70 percent of the 1 RM resistance.
Due to the slower heart rate increase on a repetition-by-repetition basis, training with 70 percent of maximum weight-load is recommended for persons with cardiovascular concerns. By wearing a heart rate monitor, trainees may safely perform strength exercises within physician-prescribed heart rate ranges. Clearly, heart rate-monitored strength training is just as important as heart rate-monitored aerobic activity for cardiac rehabilitation patients, post-surgery participants, elderly exercisers and other high-risk individuals. Of course, monitoring heart rate can also be useful for determining individual recovery periods between successive sets or exercises. For example, people requiring a more full recovery could wait until their heart rate is within 10 beats of the resting level before performing their next bout of exercise.
REFERENCES
1. American College of Sports Medicine. The recommended quantity and quality of exercise for developing and maintaining cardio-respiratory and muscular fitness in healthy adults. Medicine and Science in Sports and Exercise 22: 265-274, 1990.
2. Westcott, W. Strength training and blood pressure. American Fitness Quarterly 5: 38-39, 1986.
3. Westcott, W., and B. Howes. Blood pressure response during weight training exercises. National Strength and Conditioning Association Journal 5: 67-71, 1983.
4. Westcott, W., and S. O’Grady. Strength training and cardiac postrehab. IDEA Personal Trainer 9(2): 41-46, 1998.
5. Westcott, W., and T. Baechle. Strength Training For Seniors. Human Kinetics: Champaign, Ill., 1999.
Wayne L. Westcott, Ph.D., is fitness research advisor at the South Shore YMCA in Quincy, Mass., and author of 21 books on strength training.
Baylor University Athletic Recruiting.
Women And Heart Disease. What You Need To Know.