Short-term, Home-based, High-intensity Interval Training (HIT) for Improving Fitness

This study will aim to evaluate the efficacy of a short-term, home-based, high-intensity interval (HIT) programme in improving cardiovascular fitness in healthy volunteers aged 55 and above, with an age-comparison to younger individuals taking part in the same training regime.

It will also explore the efficacy of time-matched 'static' interventions for improving cardiovascular parameters in middle-aged females and older adults.

Patients with lower peak oxygen uptake have higher mortality and morbidity when undergoing major surgery. Aerobic fitness is a potentially modifiable risk factor for postoperative complications.

Traditional pre-operative exercise interventions to improve fitness involve high time and supervision-demands, often resulting in poor compliance. High-intensity interval training (HIT) is a time-efficient, feasible method to improve pre-operative fitness, however current studies only involve exercise in the laboratory setting.

Study Design Thirty-six healthy volunteers aged 55y and over will be randomly allocated to one of three groups: 1) Laboratory-HIT; 2) Home-HIT; 3) No intervention. All HIT sessions will involve a brief warm-up, followed by five 1-minute bouts of high-intensity (body-weight based) exercise, interspersed with 90-seconds recovery, concluding with a brief cool-down. The primary endpoint of the study is change in VO2 peak with secondary endpoints of changes in: anaerobic threshold, insulin sensitivity and muscle mass.

Subjects will be expected to perform up to a maximum of 16 HIT sessions (maximum 5 sessions per week) within a period of 31 days. Aerobic fitness will be assessed prior to and following the exercise, as will body composition, muscle structure, physical function and insulin sensitivity.

For the age comparison, 24 young individuals will be recruited to either a control or home-HIT arm.

In addition, the efficacy of time-matched 'static' interventions for improving cardiovascular parameters in 24 middle-aged females will also be assessed as exploratory work for these interventions.

The efficacy of the static interventions in older adults at home will also be explored.

Power calculation: The investigators performed a power calculation for the primary outcome of VO2 max in older adults using data from a previous study at our centre on home versus laboratory HIIT. Assuming an effect size F of 0.6 for three groups and a within group SD of 5, the alpha level was set at 0.05 and the 1-beta at 0.80. This concluded that 30 participants would be required. To allow for potential non-completion and missing data 36 older participants will be enrolled to the study (12 to each group).

Eligibility Criteria:
Inclusion Criteria:

Age \> 55 years Able to give informed consent

Exclusion Criteria:

* Current participation in a formal exercise regime
* A BMI \< 18 or \> 35 kg·m2
* Active cardiovascular disease:

  * Uncontrolled hypertension (BP \> 160/100)
  * Angina
  * Heart failure (class III/IV)
  * Significant arrhythmia
  * Right to left cardiac shunt
  * Recent cardiac event
* Taking beta-adrenergic blocking agents
* Cerebrovascular disease:

  * Previous stroke
  * Aneurysm (large vessel or intracranial)
  * Epilepsy
* Respiratory disease including:

  * Pulmonary hypertension
  * Significant COPD
  * Uncontrolled asthma
* Malignancy
* Metabolic disease e.g. diabetic patients
* Clotting dysfunction
* Significant Musculoskeletal or neurological disorders
* Family history of early (\<55y) death from cardiovascular disease