businesses Twitter
6.2.4. Preliminary testing
Prior to main trials participants visited the laboratory for two preliminary trials; (i) participant screening and (ii) exercise familiarisation.
6.2.4.1. Participant screening
Before the start of any study procedures participants provided formal written consent.
Participants underwent screening and preliminary anthropometric measures. After familiarisation with the laboratory environment, test equipment and test procedures, participants also completed two preliminary exercise tests.
Participants were provided with a participant information sheet (Appendix M), describing the purpose, protocol, demands of the study and any potential risks or harms of taking part.
Participants were allowed at least 48 h to read over the participant information sheet. After further verbal explanation of the study and discussion of any questions, participants completed an informed consent form (Appendix N). Written informed consent was obtained by means of participant dated signature and dated signature of the designated researcher who presented and obtained informed consent. The informed consent process was undertaken in privacy. The researcher taking consent was adequately trained, following completion of a Good Clinical Practise and Consent for Research training course.
Experimental procedures began with the completion of a set of questionnaires to help determine participant’s suitability to take part in the study. Specifically, participants completed questionnaires (Appendix S) to assess;
health status (health screen questionnaire)
physical activity readiness (PAR-Q)
food preference and breakfast pattern questionnaire
dietary habits (TEFQ)
The health status questionnaire screened for regular medication use and recent history of infectious disease. The PAR-Q is a validated questionnaire, used to determine if physical activity could pose a problem or hazard to participants. Tolerance to food items available at the standardised and buffet meals was assessed using the food preference questionnaire, those expressing a dislike for >20% of the food items available were excluded from the study.
disinhibited and restrained eating). Participants scoring 11 or more for any factor on the TFEQ were considered to exhibit restrained or disinhibited eating tendencies, and consequently questionnaires were further scrutinised before determining suitability to take part in the study.
Height was measured to the nearest 0.1 cm using a stadiometer (Seca Ltd, Germany) and body mass was measured to the nearest 0.1 kg using a segmental body composition analyser (Tanita, Illinois, US). Body fat percentage was measured using bioelectrical impedance (Tanita, Illinois, US). For measurements of height, body mass and body fat percentage participants wore light clothing and removed their shoes and socks. BMI was subsequently calculated as body mass in kilograms divided by squared height in metres. Waist circumference was determined as the narrowest part of the torso between the xiphoid process and the iliac crest (Ross et al. 2008). A manual sphygmomanometer and stethoscope was used to measure resting blood pressure. An appropriately sized blood pressure cuff was selected and positioned over the brachial artery. Measurements were taken in triplicate after sitting for at least five min and the mean of these were used.
A fasting blood sample was collected to confirm that participants were non-diabetic (fasting glucose concentrations <7 mmol.L-1, HbA1c <6.5%), and for the measurement of fasting total cholesterol, high density lipid-cholesterol, low density lipid-cholesterol and triglyceride concentrations. To measure glucose, cholesterol and triglyceride a blood sample was collected from the participant’s finger using a lancet (Accu-Check Lancets, Roche, Basel, Switzerland). Samples were immediately dispensed onto test strips and analysed using hand held monitors (Accutrend Plus, Roche, Basel, Switzerland and CardioChek, PTS diagnostics, Indianapolis, USA). For the measurement of HbA1c, a venous blood sample was collected by venepuncture of an antecubital vein.
All participants underwent a 12 lead resting echocardiogram (ECG), performed by a suitably qualified member of the research team. The results from the resting ECG determined whether the participant was suitable to continue in the study, or if further ECG examination was required under exercising conditions in a clinical setting by trained staff.
Finally, a suitably trained member of staff performed a physical examination of the participant to assess the nervous, pulmonary and circulatory systems for abnormalities. A
verbal detailed medical history was also obtained, and this subsequently determined the suitability of the participant to continue in the study.
Provided it was determined safe for participants to exercise, participants completed two preliminary exercise tests on a level motorised treadmill (Technogym Excite Med, Cesena, Italy). After familiarisation with the protocol and treadmill, participants completed a 16 min progressive submaximal test, as described in Chapter 4. The initial treadmill speed was set between 4.0 and 8.0 km·h-1 depending on the fitness level of each participant and was increased between 0.5 and 1.0 km·h-1 after the completion of each 4 min stage. Oxygen consumption and carbon dioxide production were determined from continuous breath-by-breath analysis (MetaMax 3B, Cortex, Biophysik, Leipzig, Germany). Prior to sample analysis, the analyser was calibrated with certified reference gases. The Borg scale was used to obtain the participants RPE at the end of each 4 min stage (Borg 1973). This scale ranged from six (no exertion) to 20 (maximal exertion). Heart rate was measured throughout using short-range radio telemetry (Polar T31; Electro, Kempele, Finland).
After a period of rest, dictated by the participant, participants completed a V̇O2 peak test. An incremental uphill treadmill protocol was used to test participants’ until volitional exhaustion.
Run speed was constant and set at a speed corresponding to a heart rate of ~150 beats·min-1. Treadmill gradient began at 1% and increased by 1% at 1 min intervals until exhaustion, which was reached within 5 to 18 min. Samples of expired air and heart rate were collected throughout. Measures of RPE were collected at the end of each 1 min stage.
To ensure attainment of V̇O2 peak participants were required to meet ≥2 of the following criteria:
plateau in oxygen consumption
heart rate within 10 beats·min-1 of age predicted maximum
RER≥1.1
RPE≥19 (Cooke 2001)
The achieved V̇O2 peak of each participant was used in combination with individual walking/running speed-oxygen uptake regression equations to determine a walking/running speed corresponding to 60% V̇O2 peak. Participants started at this speed during familiarisation trials, with subtle adjustments made if necessary i.e. for cardiovascular drift.
Participants visited the laboratory on a second occasion for an exercise familiarisation trial, at least 7 days after the screening visit. Participants performed 60 min of continuous treadmill exercise on a level motorised treadmill (Technogym Excite Med, Cesena, Italy) at a speed predicted to elicit 60% V̇O2 peak. Work rate was measured throughout (MetaMax 3B, Cortex, Biophysik, Leipzig, Germany) to monitor the intensity of the treadmill exercise, with adjustments made to the treadmill speed if necessary. Heart rate was also measured throughout (Polar T31; Electro, Kempele, Finland). Ratings of perceived exhaustion were collected at 15, 30, 45 and 60 min.
To ensure that participants adhered to the strict dietary and physical activity standardisation before each main trial, participants were given verbal and written instructions at the familiarisation visit. Specifically, participants were reminded to refrain from alcohol, caffeine, and taking part in any structured form of physical activity in the 48 h before each main trial.
An explanation was provided for how to record and subsequently replicate dietary intake before each main trial using a weighed food diary. Before the first trial participants recorded their dietary intake for 48 h and were instructed to consume identical amounts of food and drink items, at identical times, in the 48 h before the second trial. Participants were provided with a food record diary and set of food weighing scales, if required, to assist with this.
Participants were provided with food to consume the eve before each main trial, along with verbal and written instructions on how to prepare this meal. This meal was the final meal consumed before each trial and was consumed before 21:00, water was available ad libitum after this time. Participants were instructed to note the time this meal was consumed on the eve of the first trial, and this was to be strictly matched on the eve of the second trial.
Participants were asked to confirm that they had adhered to the dietary and exercise standardisations before starting each experimental trial day.
6.2.5. Experimental protocol
Participants completed two main trials (control and exercise) in a crossover design with each trial being separated by at least 7 days in males, and by 28 days in females to control for the effects of the menstrual cycle (Figure 6.4).Each trial lasted 8 h and commenced at 09:00 after an overnight fast of at least 12 h.
The exercise trial commenced with 60 min continuous treadmill exercise (Technogym Excite Med, Cesena, Italy). The speed of the treadmill was set to that determined in the exercise familiarisation trial to elicit 60% V̇O2 peak. Heart rate and expired air samples were collected by breath-by-breath analysis (MetaMax 3B, Cortex, Biophysik, Leipzig, Germany) throughout the treadmill session. Ratings of perceived exertion were assessed at 15, 30, 45 and 60 min during the exercise. Energy expenditure during the exercise session was calculated from oxygen uptake and carbon dioxide production (Frayn, 1983). These measurements were also used to calculate RER (carbon dioxide production divided by oxygen consumption). After the run participants rested in the laboratory for 7 h (sitting, reading, working at a desk or watching films). Blood samples and appetite questionnaires were completed periodically. Set meals were provided at 1.5 h and 4 h, and a buffet meal at 7 h.
The procedures in the control trial were identical to the exercise trial except that no exercise was performed. The sole exception to this was that resting expired air samples were collected during the first hour to assess resting metabolic rate. These data subsequently permitted the calculation of net exercise energy expenditure i.e. gross exercise energy expenditure during exercise minus resting energy expenditure.
Figure 6.4. Schematic representation of the main trial protocol. VAS, visual analogue scale.