Vitamin D and Exercise to Improve Physical Function in Older Adults

INTERVENTION: 4000IU/day vitamin D plus progressive multi‐modal exercise training. The 24‐week intervention period is divided into two 12‐week phases: "pre‐training", involving commencement of 4,000 International Units per day of vitamin D3 or placebo, and "training", involving commencement of the exercise protocol while maintaining the vitamin D supplementation protocol. The exercise protocol consists of three sessions per week. It will be administered by a trained exercise scientist in a group session once per week and then the participants complete a further two sessions at their home unsupervised. The training consists of progressive lower limb resistance and aerobic training targeting improvements in mobility and cardiovascular fitness. At the end of pre‐training compliance by capsule count will be conducted as a proxy for adherence to the protocol. Each session consists of a warm‐up (slow walking and stretching, 10 minutes), followed by approximately 1 hour of aerobic training (moderate‐intensity walking or jogging, approximately 30 minutes) and resistance training (leg‐strengthening exercises including knee extension and flexion, squats, side leg raises and calf raises, approximately 30 minutes), and a cool‐down (slow walking and stretches, 10 minutes). Participants will be instructed to complete aerobic and resistance training exercises at moderate intensity, based on self‐perceived exertion reported on the Borg scale. All participants will be provided with adjustable leg weights for the purpose of completing resistance training during home‐based exercise. Participants will be instructed on the use of these weights during supervised sessions, where assessments will be performed to determine whether participants are ready to increase weight amounts for the subsequent week. Participants will also be provided with an instruction booklet, along with their physical activity diary, which details exercise movements and use of leg weights. Supervisors will monitor the conduct of the participants to ensure safety. CONDITION: Cardiometabolic Health Insulin Resistance Mobility Limitation Sarcopenia PRIMARY OUTCOME: Insulin sensitivity by measuring serum glucose and insulin conducted by trained technicians from Monash Pathology at Monash Medical Centre Physical function (1) hand grip strength using a Jamar hydraulic hand grip dynamometer (Lafayette Instrument Company, USA) (2) Knee Extension Strength in both legs using a Baseline cable tensiometer (Fabrication Enterprises, USA) (3) 400 Metre Walk time measured by a stopwatch and conducted on the grounds of the hospital (4) Short Physical Performance Battery consisting of Repeated Chair Stands from a normal chair, Standing Balance, Gait Speed Test on a short 2.44m walking flat course (5) Stair Climb Power Test conducted in the stairwell of a flight of 10‐steps. SECONDARY OUTCOME: Body composition assessed by way of a whole‐body dual‐energy X‐ray absorptiometry (DXA) scan (Hologic Discovery W, Hologic, USA). Bone health: Peripheral quantitative computed tomography (pQCT) scans will be performed in the participant’s non‐dominant lower‐leg. Both regular (Stratec XCT 3000, Stratec, Germany) and high‐resolution (HR‐pQCT; Scanco Xtreme CT II) scans of the tibia will be performed. Inflammation by measuring serum high‐sensitivity C‐reactive protein conducted by trained technicians from Monash Pathology at Monash Medical Centre, Vascular health: Blood pressure and Arterial Stiffness will be measured using a digital blood pressure and pulse wave analysis monitor (Mobil‐O‐Graph, NG apparatus, I.E.M., Stolberg, Germany). INCLUSION CRITERIA: Community‐dwelling; age 55‐80 years; BMI 25‐40 (overweight or obese); low vitamin D status (serum 25‐hydroxyvitamin D [25OHD] less than or equal 49.9nmol/L); willing, and has GP approval, to complete a 12‐week exercise intervention, willing to be randomised to either vitamin D or placebo.