The present study will investigate the effect of acute exercise on fasting and postprandial risk markers for coronary heart disease (CHD) in healthy male cigarette smokers and non-smokers.

Participants will complete two, 2-day trials in a random crossover design separated by an interval of at least 1 week. On day 1, participants will rest (control) or complete 60 minute of treadmill exercise at 60% of maximum oxygen uptake (exercise). On day 2, participants will rest and consume two high fat meals (breakfast and lunch) over an 8-h period during which 13 venous blood samples and nine blood pressure measurements will be taken at pre-determined intervals.

It is hypothesised that men who smoke cigarettes will exhibit impaired fasting and postprandial metabolic risk markers compared to non-smokers, but a single bout of exercise will be equally, if not more, efficacious for improving the CHD risk factor profile in smokers than non-smokers.

Cigarette smoking is a strong and independent risk factor for CHD and is associated with impaired postprandial metabolism. Previous studies suggest that postprandial metabolism and other risk markers for CHD can be improved with acute exercise in healthy non-smokers, but less is known about responses in cigarette smokers. Therefore, the present study will compare the effect of acute exercise on fasting and postprandial risk markers for CHD in healthy male cigarette smokers and non-smokers.

A total of 12 healthy male cigarette smokers and 12 healthy male non-smokers matched for age and body mass index will be recruited. Before the main experimental trials, participants will attend the laboratory for a preliminary visit to complete screening questionnaires and to undergo familiarisation, anthropometric measurements (stature, body mass, waist and hip circumference, body fat) and exercise testing to determine maximum oxygen uptake.

Participants will complete two, 2-day (08:00-17:00) experimental trials in a randomised cross over design: control and exercise. On day 1, participants will arrive at the laboratory at 08:00 having fasted overnight and a baseline fasting venous blood sample and blood pressure measurement will be taken. A high fat breakfast and lunch meal will be consumed at 08:30 and 12:00, respectively. The control and exercise trials will be identical, except a 60 min bout of treadmill exercise at 60% of maximum oxygen uptake will be performed at 14:30 in the exercise trial.

On day 2, participants will arrive at 08:00 having fasted overnight for 10 h and will rest in the laboratory until 17:00. Participants in the smokers group will be asked to stop smoking at 08:00. A high fat breakfast and lunch will be consumed at 09:00 and 13:00, respectively. Venous blood samples from a cannula will be collected in the fasted state and at 0.25, 0.5, 1, 2, 3, 4, 4.25, 4.5, 5, 6, 7 and 8 h after the breakfast meal. Resting arterial blood pressure will be measured in the fasted state and at hourly intervals thereafter.

Inclusion criteria:

• 20- to 45-year-old healthy male smokers or non-smokers;
• Be able to exercise continuously for 1 hour;
• Body mass index between 18.5 and 29.9 kg/m2;
• Weight stable for the past 3 months;
• No known contradictions to maximal exertion exercise (e.g., recent musculoskeletal injury, congenital heart disease).
• A regular cigarette smoker or non-smoker for the last 12 months according to the definition below;

The National Health Interview Survey (NHIS) definitions will be used to identify cigarette smokers and non-smokers (Link: NHIS Adult Tobacco Use):

1. Current smokers will be defined as an adult who has smoked ≥100 cigarettes in their lifetime and who currently smokes cigarettes every day.
2. Non-smokers will be defined as an adult who has never smoked or who has smoked < 100 cigarettes in their lifetime

The following questions will determine the eligibility and group allocation:

1. Do you currently smoke cigarettes on a daily basis?
2. Have you smoked at least 100 cigarettes in your entire life?

If the person answers YES to Q1 and YES to Q2 they are eligible for the study and will be allocated to the smokers group.

If the person answers NO to Q1 and NO to Q2 they are eligible for the study and will be allocated to the non-smokers group.

Individuals answering any other combination (YES, NO or NO, YES) will not be eligible to take part in the study.

Exclusion Criteria:

• Not meeting the criteria for a smoker or non-smoker (defined above);
• Current E-Cigarette smoker;
• Musculoskeletal injury that has affected normal ambulation within the last month;
• Any muscle or bone injuries that do not allow them to walk and run on a treadmill;
• Uncontrolled exercise-induced asthma;
• Heart conditions;
• Coagulation or bleeding disorders;
• Diabetes (metabolism will be different to non-diabetics potentially skewing the data);
• Taking any medication that might influence fat metabolism;
• Taking any medication that might influence blood glucose (e.g., insulin for diabetes);
• Dieting or restrained eating behaviours;
• Weight fluctuation greater than 3 kg in the 3 months prior to study enrolment;
• A food allergy.