Does Exercise Snacking Improve Muscle Function in Older Adults?

Muscle size declines at around 0.5-1% per year after 50 years of age, with muscle strength declining up to twice as fast as muscle size. This may eventually lead to loss of independence if tasks of daily living become too strenuous to be performed safely. Exercise is recognized as a safe and effective means to counteract muscle loss during aging, however access to gym equipment may be logistically challenging or unpalatable to older adults. This research is designed to investigate the effect of 28 days of home-based leg exercise that doesn't require exercise equipment or supervision (exercise snacking), accompanied with a daily protein supplement in the form of commercially available yogurt, on the skeletal muscle health (i.e. function and size) of independent, community-dwelling older adults. To achieve this, two groups will be compared; one group will undertake exercise snacking and consume a 150 g yogurt with the breakfast meal for four weeks, with the second group only receiving the daily yogurt with no exercise snacking.

The study will require potential participants to undergo an eligibility screening with a member of the research team, followed by a period of seven days of habitual activity monitoring and 3 days of diet recording. Eligible participants will be allocated into study groups by way of minimization based on sex, age, BMI, and number of sit-to-stands performed in a minute. Participants will undertake two familiarisation sessions with strength, power, neural drive, and balance tests at least seven days apart, the first following eligibility screening and the second familiarisation session at least five days before the first main trial.

Thereafter, both groups will undertake a main trial the day before commencing 28 days of daily 150 g yoghurt supplement with the breakfast meal, with the exercise snacking group (ES) also undertaking two bouts of exercise snacking a day. The main trial will include measures of leg muscle function and neural drive, standing and single leg balance, and movement co-ordination during tasks of everyday ambulation. Participants will wear a physical activity monitor and pedometer for the seven days and record diet for three days during the last week of the intervention. The day after the intervention period, a follow-up main trial will be conducted as per the first main trial, followed by an optional qualitative interview regarding participant's experience of the trial.

Eligibility Criteria:
Inclusion Criteria:

* Not underweight or obese (body mass index ≥20 and ≤ 30 kg/m2)
* Not regularly engaging in recreational sports or structured exercise (once a week or more).
* Non-smoker (for \>5 years)
* Healthy (see exclusion criteria)

Exclusion Criteria:

* Any chronic illness, cardiac, pulmonary, liver, or kidney abnormalities, uncontrolled hypertension, peripheral arterial disease, insulin- or non-insulin dependent diabetes or other metabolic disorders - all ascertained through preliminary screening.
* Individuals with a history of bone, joint or neuromuscular problems or a current musculoskeletal injury ascertained through preliminary screening.
* Individuals with any joint replacement surgical implants or other artifacts containing metal.
* Individuals with a clinically diagnosed allergy or intolerance of dairy products.
* Individuals with contraindications to exercise including chest pain, dizziness, or loss of consciousness, or who have been instructed by their doctor to only do physical activity recommended by them.
* Individuals who score less than 8 on the Short Physical Performance Battery or score zero on any component of the test.