Regular Exercise for Peripheral Arterial Ischaemia: a Randomised Intervention Trial

Progressive resistance training (PRT) or weight lifting training is a common type of strength training for developing the strength and size of skeletal muscles. It uses the force of gravity or in our case compressed air resistance to oppose the force generated by muscle through concentric or eccentric contraction. Effectively stimulating and overloading the muscle to generate muscle adaptations such as improvements in strength, endurance and power. PRT is an anabolic form of exercise, differing substantially from aerobic exercise in its ability to induce muscle hypertrophy and associated metabolic and functional changes. It has been shown in randomised controlled trials (RCTs) of similar cohorts to improve insulin sensitivity, glucose homeostasis, blood pressure, dyslipidaemia, markers of inflammation and catabolism, and visceral obesity, thus addressing virtually all of the known risk factors associated with peripheral arterial disease (PAD). PRT also improves aerobic capacity, osteoarthritis pain and disability, depression, functional status, gait and balance impairments, bone density, and insomnia, thus addressing the spectrum of associated clinical disorders in older adults with PAD. Notably, high intensity PRT is feasible when robust aerobic exercise is impossible (as in our cohort) due to osteoarthritis or advanced peripheral arterial disease. PRT has also been shown to significantly improve walking ability when compared to control and/or baseline values in asymptomatic patients and those with mild to moderate claudication. In addition PRT has also been shown to improve functional status, quality of life and well-being scores in this same cohort. We will be comparing high intensity PRT to low intensity PRT and to a control condition. Participants who receive high intensity resistance training will receive weight lifting exercises of 10 major muscle groups. Frequency of training will be 3 days per week under supervision using pneumatic resistance equipment. The exercises chosen include the large muscle groups of the arms, legs and trunk. More specifically we have chosen exercises that specifically focus on areas where claudication most commonly occurs, such as the calf or thigh. Exercises chosen include: calf plantar flexion, ankle dorsiflexion, knee extension, leg press, leg curl, hip extension, hip abduction, chest press, seated row and lat pulldown. These are symmetrical exercises and functionally relevant to activities of daily living, as well as gait performance, both of which are affected by intermittent claudication. For each exercise participants will perform 3 sets of 8 repetitions, with controlled concentric and eccentric phases (4 seconds per repetition with 2 minutes rest between sets). Exercise to claudication pain was deemed unnecessary due to two recent aerobic exercise trials achieving improvements in walking distances based on a chosen exercise intensity that deliberately did not invoke claudication pain. In addition, in our experience of 25 years of working with persons with PAD, typical high intensity, low volume PRT has never caused the onset of claudication pain. However, if it does occur the participant will be encouraged to continue exercising to complete the set. If the pain becomes unbearable, they will be allowed to stop and rest until the pain dissipates enough for them to complete the set. In addition this group will receive usual medical care advice on foot care, lifestyle change, such as quitting smoking, and maintaining a healthy weight. Advice on completing walking exercise will not be provided. The initial intensity for the high intensity treatment group will be set at 50% of the most recently determined peak strength (1 repetition maximum or 1RM). Intensity will then be increased each session, over a 2 week period until 80% 1RM has been reached. Resistance used will be increased by about 3% per session or as tolerated using Borg scale rating of perceived exertion on a continuous basis throughout the 6 months. Repetition maximum testing will be repeated at 2 week intervals to ascertain progress and regulate intensity. All training will be fully supervised by skilled exercise physiologists to maintain proper intensity and progression, as well as to ensure correct technique. Supervision was deemed necessary for both groups as a recent meta-analysis demonstrated that supervised exercise therapy showed statistically significant and clinically relevant differences in improvements of maximal treadmill walking distance compared with non-supervised exercise regimens. Therefore both training groups will be exercising within a group of up to four participants per one exercise physiologist for approximately one hour, 3 days per week for an overall duration of 6 months. The low intensity training protocol was designed with the intention of mimicking many current community resistance training intensities. Participants who receive low intensity resistance training will be trained by the same exercise physiologists in the same facility under the same training protocol. The one exception will be the change in intensity. The initial intensity for this treatment group will be set at 20% of the most recently determined peak strength (1 repetition maximum or 1RM). Intensity will then be increased each session, over a 1-2 week period, in 3% increments until 30% 1RM has been reached, and the load will be maintained at that level for the duration of the 6-month trial. In addition, as with the high intensity group, this group will receive usual medical care advice on foot care, lifestyle change, such as quitting smoking, and maintaining a healthy weight. Advice on walking exercise will not be provided.