Citrulline, Exercise Training and Muscle Strength in the Elderly

Maintaining muscle strength is mandatory for elderly persons to keep autonomy. Resistance exercise increases muscle strength in old and very old subjects, but there seems to be little effect on muscle mass. Citrulline is an amino acid that stimulates muscle protein synthesis, but its effect on muscle strength and mass remains to be determined. The aim of this study is to assess the effect of citrulline supplementation on muscle strength in elderly institutionalized subjects undergoing a resistance exercise training program.

All the subjects (84) will undergo a resistance exercise training program for 12 weeks. The subjects will have a regimen of high-intensity progressive resistance training of the knee extensors 3 days per week. These muscle groups were chosen because of their importance in functional activities. The subjects will be randomized into two groups. An intervention group will receive orally citrulline at 10 g/day, and a control group will receive an isonitrogenous amount of nonessential amino acids (alanine, aspartate, glycine, serine, histidine and proline in equimolar quantity). During the 12 weeks of supplementation, clinical tolerance will be evaluated. Strength testing will be repeated every two weeks for 12 weeks. The primary endpoint is the outcome of maximum strength of knee extensor muscles. Fat-free mass (DEXA), gait velocity, timed get up and go, spontaneous physical activity (activity monitors), nutritional status (weight, albuminemia, TRANSTHYRETINEMIA) and quality of life will be measured at inclusion and at the end of the study. The number of falls during the study will be recorded.

Inclusion criteria

• Aged over 75 years
• Able to walk at least 6 meters without human assistance.

Exclusion criteria

• Moderate to severe cognitive disorders (MMSE < 20)
• Severe malnutrition (BMI < 18 or weight loss > 10 % in 1 month or > 15 % in 6 months, or albuminemia < 30 g/L),
• Inflammation (CRP > 30 mg/L),
• Severe renal failure (creatinine clearance < 30 mL/mn),
• Stage 4 cardiac failure,
• Respiratory failure,
• Corticoid treatment,
• Participation in another trial