[Editor’s Note: Following is a reprint of an article published a number of years ago on the PERF website.]
By Tom Storer, Ph.D.
Hello from the Strength Lab. Last time, we talked about the value of resistance exercise training (weight training) for pulmonary patients as part of a comprehensive program of pulmonary rehabilitation. This follow-up presents more on strength training, specifically the considerations in structuring a resistance training program for people with COPD. Surprisingly, not a lot is known about the optimal design of weight training programs for this application. While it is well acknowledged that muscle atrophy and the accompanying decline in physical function does accompany lung disease, guidelines for specifically rehabilitating muscle in patients with lung disease are lacking. What we do know about resistance exercise in pulmonary rehabilitation has come from a very few published research studies demonstrating the excellent trainability of people with lung disease as well as from extrapolations of guidelines developed for healthy populations.
The basic elements included in a good program of resistance exercise training include:
Days per week per part: this element identifies how many days an individual will exercise any given muscle or muscle group.
Figure 1 illustrates the major muscles and muscle groups that should be regularly exercised. Current recommendations in healthy populations suggest a minimum of two days per week, although three days per week may bring about greater, but not necessarily proportional improvements.
Exercises per body part: several different exercises are available to train each muscle. Decisions must be made regarding how many exercises are appropriate for each part.
Sets per exercise: one of the biggest areas of discussion in resistance exercise prescription today centers around the number of sets (the number of complete cycles or repetitions of an exercise) that should be performed for each exercise. Is one set enough? Will three sets give a much better result?
Rest interval: this guideline specifies the length of time a person should recover between sets of an exercise. Rest periods may be as short as 15 seconds or as long as 2-4 minutes. In people who experience shortness of breath upon exertion, longer rest periods may be necessary to maintain adequate oxygen saturation.
Repetitions per set: a repetition is one complete cycle (the up and down parts) of an exercise. The number of repetitions per set may vary with goals, training experience, or phase of training.
Load: In resistance exercise training, load refers to the amount of weight or resistance moved during the exercise. Load is often prescribed on the basis of a standard test for strength known as the one-repetition maximum test (1-RM). The 1-RM is the maximum amount of weight that can be lifted one time only in any particular exercise. Load prescriptions typically utilize 50-100% of this 1-RM weight. Alternatively, load can be assigned on the basis of completing a certain target number of repetitions before the weight can no longer be lifted. We refer to this as the xxRM method, with xx indicating some number of repetitions. For example, an exercise prescription might call for 8-12 RM. This means that the trainee would select a weight that could be lifted in good form at least 8 times, but not more than 12 times.
How has the research guided us in the design of resistance exercise training programs? A synthesis of the published studies investigating the trainability of muscle in patients with lung disease would suggest training frequencies of 2-3 days per week, with 1-3 sets of 8-10 repetitions utilizing loads progressing from 50 to 85% of a current 1-RM assessment. Typically, rest intervals have not been reported, but our experience in the El Camino College Pulmonary Fitness Program (ECC-PFP) suggests 1-2 minutes as an appropriate range. Studies utilizing some combination of these guidelines have demonstrated substantial improvements in muscle strength and size in patients with mild to moderate COPD. In our ECC-PFP, we have documented in 12 participants with COPD, 84% and 87% improvements in leg muscle and chest muscle strength, respectively, over the course of three years (Figure 2).
Most of this improvement occurred within the first 8-9 months. However, strength has continued to increase over the three year period of observation.
Some recent resistance training guidelines recommended for healthy individuals have suggested use of a single set of 8-12 repetitions to fatigue. However, specific exercise and physical activity guidelines for older adults (the majority of patients with COPD fall into this group) recommend 2-3 sets. We have found that a single set of one exercise for each body part may be an ideal starting point for people with COPD, but principles of progression suggest that, to maximize the response, two or possibly three sets would be more advantageous as the patient progresses. This could take the form of 2-3 sets of one exercise or a single set of two or more exercises per muscle or muscle group. Some muscles or muscle groups might receive more training than others. For example, large leg muscles, which are important for walking, stair climbing, and getting up and down from a chair might benefit from multiple set training. A consideration in choosing a number of sets is the time available for the training sessions in the context of a complete and balanced exercise program. We have long appreciated the value of aerobic exercise training, as well as stretching and flexibility exercises in a comprehensive pulmonary exercise program. These aspects, of course, take time.
In our experience, fewer rather than more repetitions seem to be better tolerated by the COPD patient, with 6-10 repetitions appearing optimal. However, some patients should begin resistance exercise training with lighter loads and more repetitions such as in the 8-12 range. As strength increases and joints, ligaments, and tendons adapt to new stresses, the load can be appropriately increased with a complementary decrease in repetitions. As with endurance training, a gradual introduction to resistance training, perhaps with 1 set of 8-12 repetitions using 50-60% of 1-RM for major muscle groups, will avoid excessively sore muscles and allow the participant to establish a training base from which one may progress. We typically see our beginning patients able to progress to a second set within 3-4 weeks of twice-weekly training. After another 3-4 weeks of adaptation, most patients can tolerate increased percentages of newly established 1-RM values. Loads for the lower extremity exercises can generally increase by 10% whereas a 5-7% increase in percent 1-RM for upper extremity exercises is more appropriate.
Other considerations in the formulation of a resistance training program for people with COPD include the type of resistance used, choice of exercises, and safety considerations. Many types of resistance are available including elastic resistance, machine weights, free weights, and body weight. Choice of equipment is often dictated by what is available. However, almost any form of resistance will suffice so long as it can be graded in its application, is safe to use, and has some motivational appeal to the participant. The latter is often accomplished when the participant sees a known amount of weight move. Consideration should be given to the minimal weight that can be set for any given exercise. Some types of weight machines have minimal resistances that are too high or weights that are in increments that are too large for some debilitated COPD patients. The ideal rest interval between sets is difficult to establish for the patient with COPD primarily because of varying degrees of dyspnea and/or oxyhemoglobin desaturation. While a one-minute rest interval between sets might be attempted, in practice, 2-3 minutes may be required. Number and choice of exercises may be dictated by patient goals (e.g., improving ability to climb stairs in the patient’s domicile) or by contraindications such as arthritic joints or osteoporosis (a particular problem in patients undergoing long-term corticosteroid therapy). A free weight squat, for example, would typically not be appropriate in the COPD population. However, performing the seated leg press exercise or repetitions of standing up from a bench or chair while holding progressively heavier dumbbells on the hips may be acceptable alternatives. If patients cannot stand up from the chair or bench with their body weight alone, the seat height may be elevated.
Resistance training, even at high intensities has been shown to be safe and beneficial for healthy older adults. No untoward responses have been reported in resistance training studies with COPD patients even with training intensities as high as 85% 1-RM. Additional safety concerns include the need to use a biomechanically safe lifting technique. Part of the correct lifting technique includes proper breathing, avoiding the Valsalva maneuver [breath holding]. In order to help maintain oxyhemoglobin saturation levels in the appropriate range (90%), diaphragmatic and pursed lip breathing may be performed as necessary. It may be necessary to periodically monitor oxygen saturation with a pulse oximeter and level of dyspnea with a visual analog scale. Periodic blood pressure measurements are needed in order to monitor the pressor response to the resistance exercise.
While these training strategies have been shown to be safe and effective in improving muscle strength, size, and function in small groups of patients, they should be viewed as suggestions only; further research will be needed to establish firm resistance training guidelines for COPD patients. It is clear, however, from the existing published research on resistance exercise training in COPD, as well as our four years of experience in adding weight training to pulmonary exercise programs that patients with COPD are responsive to resistance training and can make and sustain significant improvements in strength. Future research will help in the design of optimal training programs for these patients in order to overcome the muscular weakness and loss of functional ability that attends this disease.
Next time, I’ll give you illustrations and descriptions of basic resistance training exercises. Be sure to obtain physician approval before starting off on your own. Better yet, get that approval and join your friends in a structured pulmonary exercise program.
Tom Storer, Ph.D. is a former member of the PERF Board of Directors. He is also a popular exercise physiologist with a great deal of “hands-on” experience in dealing with the problems experienced by patients with respiratory disease.