High-intensity Interval Training and Mixed Meal Responses in Persons With Spinal Cord Injury

Persons with chronic paraplegia at an increased risk of developing cardiovascular disease and type-2 diabetes compared to the able-bodied population. There is mounting evidence from the able-bodied literature that high-intensity interval training (HIIT) is more effective than moderate-intensity continuous training (MICT) at improving markers of cardiometabolic health. Before we can understand the long-term training effects of HIIT in this population, it is important to compare the acute metabolic responses to a typical mixed-macronutrient meal following both exercise modalities.

This study is recruiting adults (aged 18-65 years) with paraplegia (T2 or below) who sustained their spinal cord injury more than one-year ago. Participants will need to attend the laboratory at the University of Bath on four separate occasions, once for preliminary testing, and three times for study trials.

The aim of this research is to determine the metabolic responses to a mixed-meal tolerance test following a bout of HIIT and MICT in persons with chronic paraplegia. The hypothesis is that HIIT and MICT will be more effective at reducing the total triglyceride responses compared to a resting control condition.

Preliminary measurements:

Preliminary testing will include anthropometric measurements of supine length, weight, waist and hip circumferences, and resting blood pressure. There will also be an assessment of resting metabolic rate, sub-maximal and maximal exercise capacity, and a HIIT familiarisation session. All of the exercise protocols will take place on an arm crank ergometer at the University of Bath.

Physical activity monitoring:

For 7 days, participants will be fitted with a physical activity monitor (Actiheart™). Participants should not make any conscious changes to their normal lifestyle habits/routines during this period.

Main trial days:

In the 2 days prior to the main trial day, participants will be asked to record their food and drink intake and 48 hours before they should refrain from performing any strenuous physical activity. In the 24 hours prior participants should also refrain from consuming any alcohol or caffeine.

Following a 10-hour overnight fast, an expired gas sample and venepuncture blood sample will be taken prior to exercise. Participants will then perform a bout of HIIT, MICT or a resting control condition. Following exercise, a cannula will be inserted into a vein and baseline blood sample(s) taken for analysis of metabolic markers.

The participant will then be asked to consume a smoothie, consisting of peanut butter, banana, coconut oil, sugar, and chocolate-flavoured whey protein powder. The meal should be consumed within 10 minutes and blood samples will be taken from the cannula at 15, 30, 45 60, and 90 minutes and then at every hour for 6 hours after consumption of the meal to monitor changes in metabolic and inflammatory markers. Expired gas samples will also be taken hourly and indirect calorimetry will be used to estimate relative fat and carbohydrate metabolism in response to the meal.

Eligibility Criteria:
Inclusion Criteria:

* Individuals with a chronic (\>12 months post-injury) SCI below T2
* Individuals who spend \>75% of their waking day in a wheelchair
* Weight stable (weight not changed by \>3% over the last 3 months)

Exclusion Criteria:

* Individuals who an acute (\<12 months post-injury) SCI
* Individuals who spend \<75% of their waking day in a wheelchair
* Individuals on type-2 diabetes medication
* Individuals with a peanut allergy
* Individuals who self-report use of lipid-lowering agents
* Individuals self-reporting active medical issues (pressure sores, urinary tract infections, cardiac disorders, musculoskeletal complaints of the upper extremities, or cardiovascular contraindications to exercise testing)
* Individuals who report uncontrolled or regular autonomic dysreflexia