Combined exercise and nutritional intervention
Participants were divided into groups of two to three individuals, and each group visited our institute biweekly for 12 weeks. In each session, a 50-minute exercise program for spinal extensor strengthening was executed. Exercise intensity was determined by measuring the amount of time (in seconds) that each motion was maintained per set. Before and after each session, 5-minutes of warm up and cool-down on the major muscle groups was included. The back extensor strengthening exercises included (1) 5-minutes of McKenzie back extension exercise; (2) 5-minutes each of curl-up, side-bridge, and bird-dog exercises; (3) 10-minutes of plank exercises (basic > elbow > one-side); and (4) 10-minutes of squatting exercise. An exercise booklet describing the back extensor strengthening exercises was provided to each participant so they could follow the regime of exercising three times per week (including bi-weekly visits to the institution). In the initial evaluation, exercise intensity was individually defined, based on the number of repetitions and maintenance time of each exercise. On their visit to the institution every two weeks, the exercise intensity was increased by 20% so that progressive resistance exercise was possible. Weekly video calls and participation checks were conducted to improve the exercise compliance.Each participant’s daily calorie and protein intake was calculated using the 24-hour recall method. A liquid protein supplement (125 mL) and an energy bar (Selex core protein; Maeil Health Nutrition Co., Ltd., Gyeonggi-do, Korea; 46 g of carbohydrates, 16 g of fats, and 20 g of proteins with 1830 mg of leucine, providing a total of 423 kcal) were provided to each participant per day for 12 weeks. The supplementation was scheduled to be taken once a day, irrespective of whether it was before or after exercise. To monitor the nutritional supplementation, participants were provided with monitoring sheets to record the time of the day on which they consumed the protein supplement; this data were collected every 2 weeks (institute visiting day) [