Conclusiones

Each participant began a water-only fast in the evening after eating dinner. In the morning (after at least 10 hours fasted) participants underwent an oral glucose tolerance test (OGTT) in order to establish fasting insulin/glucose levels and insulin/glucose levels 2 hours after a glucose load. After a light breakfast following the OGTT, body composition was measured by hydrodensitometry. Participants then performed a treadmill test to establish their VO2max.

In following with a kaupapa Māori approach, I aimed to promote whanaungatanga among the research participants, a concept associated with building relationships and finding common ground, so testing sessions were done in groups of 3-4 men, rather than individually. Participants also shared meals, before and after testing, in order to build relationships between researchers and participants. In most instances, karakia (prayers) were also offered before testing sessions. At the conclusion of the study, all participants received a compiled report of their results as well as the mean results of the group and population norms.

5.2.3.1 Blood biochemistry

After an overnight fast (10-12 hours post-prandial), participants underwent a standard oral glucose tolerance test (OGTT) at an accredited blood pathology lab (Aotea Pathology Ltd, Wellington). Fasting blood samples were collected for analysis of fasting glucose (FastGluc) and fasting insulin (FastIns) before a 75ml glucose beverage was given. Two hours after the glucose load was taken, blood samples were again collected for analysis of glucose and insulin, 2 hours post-glucose load (2hrGluc & 2hrIns).

Analysis of blood was also performed at these accredited laboratories where serum was extracted and frozen for analysis. Serum Glucose concentrations were measured using a

Roche 917 autoanalyser with Gluco-quant® kits (Roche Diagnostics, Manheim, Germany). Serum insulin was measured with a Roche Elecsys® 2010 via an immunometrical method using electrochemical illuminescence. Blood biochemistry followed the same methods used by Stannard et al. (Stannard, Holdaway, Sachinwalla, & Cunningham, 2007). Extraction and analysis of blood was performed at the same lab in Wellington for both arms of the study.

Insulin sensitivity was estimated using the homeostasis model assessment-insulin resistance (HOMA-IR) model (Matthews et al., 1985).

5.2.3.2 Maximal oxygen uptake

Respiratory exchange of participants was measured during an incremental exercise protocol on a WOODWAY® treadmill (the Desmo ‘05’, Wisconsin, USA). The Bruce protocol (R. A. Bruce, 1971) was chosen as it was used in the initial study and was practical for those that were unfamiliar with treadmill running or were relatively unfit. Participants were encouraged to continue exercising for as long as possible, as the speed and gradient of the treadmill increased every 3 minutes, in order to obtain intensities capable of eliciting maximal VO2.

Volitional fatigue was defined as when the subject grasped the safety railing of the treadmill to finish the treadmill test.

Expired respiratory gases were sampled throughout the entire exercise test by an online gas analysis system using Moxus (version 2.1.05) software (AEI technologies Ltd, Illinois, USA). Expired air was collected via a Hans Rudolf mouthpiece with a turbine attached to measure expired volume. Expired air entered a mixing chamber and was analyzed for expired fraction of CO2 using an infrared carbon dioxide sensor and expired oxygen using a zirconium cell- based oxygen sensor (AEI, Illinois, USA).

Both the analysers and software were calibrated each morning before testing was performed using a predetermined mixture of O2 and CO2 (4.9% CO2, 15.6% O2 in Nitrogen) while the

turbine was calibrated with a 3000ml Hans Rudolf calibration syringe. Data were averaged by the software and displayed in 10 second intervals. VO2max was defined as the highest

rolling 1 minute average VO2 (six 10 second recordings) obtained during the test. VO2max

was expressed relative to lean body mass (VO2maxLBM) rather than relative to whole-body

mass as it better represents the aerobic capacity of working muscle, independent of fatness (Coon, Bleecker, Drinkwater, Meyers, & Goldberg, 1989; Stannard, Holdaway, Sachinwalla, & Cunningham, 2007).

5.2.3.3 Body composition

Hydrodensitometry was performed in the morning between 1-2 hours after a small meal (the first meal post-fast) for determination of body volume. Participants wore tight fitting shorts or a swimming costume while in the water tank. Body weight on land was measured using a Sartorius electric scale (EA Model, Goettingen, Germany) and height was measured using a wall mounted ‘Harpenden’ stadiometer (Holtain Ltd, Crosswell, UK).

Participants were given up to 10 minutes to practice the submersion technique and familiarize themselves with the procedure. They were suspended in the water by a harness-like seat attached by ropes to a force transducer sited above the tank. The transducer output, once calibrated would be amplified and converted to a digital signal and used to indicate the underwater weight of the subjects. Once familiar with what was required, subjects were asked to exhale as much air from their lungs as was comfortable while submerging completely underwater by bowing the head forward as far as was comfortable. Once the subject was fully submerged and relatively stable, the measurement of underwater weight began using Labview

software (Eagle Scientific, USA) programmed by our group. Participants were required to stay submerged for 5 seconds as underwater weight was measured. The software provided a graph of underwater weight, during the 5 second period. An average of the 5 second reading was taken, in order to account for the sinusoidal fluctuations in transducer output that occurred from the natural motion of the water.

After the 5 second underwater period, participants were given a signal from the operator to raise their head out of the water. After participants had raised their head out of the water, residual lung volume was measured via oxygen dilution using an oxygen re-breathing technique described by van der Ploeg et al. (van der Ploeg, Gunn, Withers, Modra, & Crockett, 2000). The re-breathing apparatus consisted of a 5L (rubber) anaesthetic bag (Vacumed, California, USA) containing 4.25L of pure oxygen attached to Hans Rudolf 3 way ‘sliding type TM’ Manual directional control valve (2870 series, Missouri, USA). A disposable ‘SureGard’ respiratory filter was used as a mouthpiece for participants, and the control valve allowed the operator to open or close the flow of oxygen from the bag to the mouthpiece.

After raising their head out of the water after the weighing, the mouthpiece of the apparatus was guided into their mouth and participants were asked not to take their first breath until the mouthpiece was securely in the mouth, the lips sealed around it, and the valve opened that allowed the participant to breathe the closed circuit oxygen. After 5-6 breaths in the apparatus, the valve was closed and the gas analysed for O2 and CO2 concentration using the

same gas analysers used in the exercise test above. Body fat percentage was then calculated using previously established methods (Brozek, Grande, Anderson, & Keys, 1963).

Each participant performed the measurement protocol at least 3 times. Percentage body fat was taken as the average of the 3 measurements. If deviation outside 2% body fat occurred, a fourth measurement was also taken, and measurements that deviated outside 2% body fat were disregarded.

Two point calibration of the load cell was performed (once with no weight and again with a 5kg weight) each morning before testing took place.