second group, we found that pure forms of aerobictraining were not used. Instead, we found that multipleforms of therapeutic exercise, including aerobic training,stretching or flexibility exercise, balance and relaxationtraining, and Tai Chi were used. Therefore, weplaced the studies using aerobic exercise plus otherinterventions into a group we called “combination training.”Combination training was used in 29 of the studies,16 studies examined changes in habitual gait speed and13 studies examined changed in fast gait speed (Tabs. 2and 3). We did not include warm-up or cool-down as acomponent of the exercise intervention because theywere included in almost every study. The Appendixcontains descriptions of the type of exercise used in thehabitual and fast gait speed studies.Exercise intensity and dosage. The effect of exerciseintensity was examined in the 24 habitual gait speedstudies. Participants in 10 studies performed a highintensityexercise program, participants in 5 studiesperformed a moderate-intensity exercise program, andthose in 9 studies performed a low-intensity exerciseprogram (Tab. 2). Exercise intensity was categorizedbased on primary research and guidelines56–58 from theavailable information and data in the articles. Researchresults support the use of 60% to 80% of the 1-RM levelto produce a strengthening effect in untrained individuals.54 For strength training programs, the exerciseprograms were classified as high intensity if exerciseswere performed at 60% to 80% of the 1-RM level. Theexercise programs were classified as moderate-intensitystrength training when resistance was progressed, butnot in a specified manner, and when unsupervisedexercise sessions were included. The exercise programswere classified as low-intensity strength training wheninsufficient information was provided to place them intoeither of the other groups. For the combination trainingprograms, high-intensity exercise was denoted whenparticipants worked at 70% to 85% of HRR or 80% ofAPHRM.57 For moderate intensity, 50% to 69% of HRRor 60% to 70% of APHRM was used. Finally, 50% ofHRR or 60% of APHRM was considered a low-intensityexercise program.57As with exercise intensity, the effect of exercise dosage(duration of the exercise sessions and frequency ofexercise bouts per week) was examined in the 24 studiesfor habitual gait speed. Research findings56 and AmericanCollege of Sports Medicine (ACSM) guidelines onstrength training58 recommend that training be done fora minimum of 2 days a week, 4 sets per muscle group,with a warm-up and a cool-down. For aerobic exercise,the literature and ACSM guidelines support the use of 20to 60 minutes of exercise per session, for 3 to 5 days perweek, to produce an effect for endurance training.58,59To determine exercise dosage, the total minutes of