Outcome
Type |
Measure |
Description |
Time frame |
Safety issue |
Primary |
Change in blood pro-peptide of type 1 collagen (P1NP) concentration |
P1NP is a marker of bone resorption and it will be measured during the fasted state |
of dietary provision to the same time on the morning following the final day of dietary provision (three days later), in each condition |
|
Primary |
Change in blood ß-carboxyl-terminal cross-linked telopeptide of type 1 collagen (ß-CTx) concentration |
ß-CTx is a marker of bone formation and it will be measured during the fasted state |
of dietary provision to the same time on the morning following the final day of dietary provision (three days later), in each condition |
|
Secondary |
Change in blood 17ß-oestradiol concentration |
17ß-oestradiol is a reproductive hormone that fluctuates during the menstrual cycle and is involved in the regulation of bone resorption |
of dietary provision to the same time on the morning following the final day of dietary provision (three days later), in each condition |
|
Secondary |
Change in blood triiodothyronine (T3) concentration |
T3 is a thyroid hormone that has previously been shown to decrease in response to low energy availability has been proposed as a useful marker of low energy availability |
of dietary provision to the same time on the morning following the final day of dietary provision (three days later), in each condition |
|
Secondary |
Change in blood ß-hydroxybutyrate (ß-OHB) concentration |
ß-OHB is a ketone body produced during periods of energy and/or carbohydrate restriction |
of dietary provision to the same time on the morning following the final day of dietary provision (three days later), in each condition |
|
Secondary |
Change in blood calcium concentration |
Calcium is a micro-nutrient involved in the regulation of bone (re)modelling and may change in response to low energy availability |
of dietary provision to the same time on the morning following the final day of dietary provision (three days later), in each condition |
|
Secondary |
Change in blood magnesium concentration |
Magnesium is a micro-nutrient involved in the regulation of bone (re)modelling and may change in response to low energy availability |
of dietary provision to the same time on the morning following the final day of dietary provision (three days later), in each condition |
|
Secondary |
Change in blood phosphorus concentration |
Phosphorus is a micro-nutrient involved in the regulation of bone (re)modelling and may change in response to low energy availability |
of dietary provision to the same time on the morning following the final day of dietary provision (three days later), in each condition |
|
Secondary |
Change in resting metabolic rate (RMR) |
This is amount of energy used by the body at rest and is measured via indirect calorimetry compared to RMR predicted using previously validated equations. It has been proposed that a ratio of <0.9 may be used as a surrogate marker of energy deficiency |
From the morning of the first day of dietary provision to the same time on the morning following the final day of dietary provision (three days later), in each condition |
|
Secondary |
Change in ratio of measured:predicted resting metabolic rate (RMR) |
This is the ratio of RMR measured via indirect calorimetry compared to RMR predicted using previously validated equations. It has been proposed that a ratio of <0.9 may be used as a surrogate marker of energy deficiency |
From the morning of the first day of dietary provision to the same time on the morning following the final day of dietary provision (five days later), in each condition |
|
Secondary |
Change in blood plasma volume (estimated using haemoglobin concentration and haematocrit) |
Plasma volume is a measure of the proportion of blood that is made up of plasma. It has been shown to change in response to low energy availability and may influence the concentrations of primary measures independent of low energy availability, per se. |
of dietary provision to the same time on the morning following the final day of dietary provision (three days later), in each condition |
|
Secondary |
Change in heart rate variability |
It has been proposed that low energy availability impairs cardiovascular function and heart rate variability is a measure of the variation in time between each heart beat |
of dietary provision to the same time on the morning following the final day of dietary provision (three days later), in each condition |
|
Secondary |
Change in the spectral density of heart rate variability in low and high frequency bands |
It has been proposed that low energy availability impairs cardiovascular function and spectral analysis of heart rate variability provides information on the function of sympathetic and parasympathetic regulation of heart rate |
of dietary provision to the same time on the morning following the final day of dietary provision (three days later), in each condition |
|
Secondary |
Change in aortic stiffness |
It has been proposed that low energy availability impairs cardiovascular function and aortic stiffness is estimated via measurement of arterial stiffness at the wrist |
of dietary provision to the same time on the morning following the final day of dietary provision (three days later), in each condition |
|
Secondary |
Change in forearm resting blood flow |
It has been proposed that low energy availability impairs cardiovascular function and forearm blood flow is a marker of cardiovascular function that can be measured using plethysmography |
of dietary provision to the same time on the morning following the final day of dietary provision (three days later), in each condition |
|
Secondary |
Change in forearm peak blood flow |
It has been proposed that low energy availability impairs cardiovascular function and peak forearm blood flow is a marker of cardiovascular function that can be measured using plethysmography |
of dietary provision to the same time on the morning following the final day of dietary provision (three days later), in each condition |
|
Secondary |
Change in body weight |
Body weight could be expected to decrease in response to caloric restriction and will therefore be measured and can be used to indicate adherence to dietary provision |
of dietary provision to the same time on the morning following the final day of dietary provision (three days later), in each condition |
|
Secondary |
Change in fat-free mass |
Fat-free mass could be expected to decrease in response to caloric restriction and will therefore be measured and can be used to indicate adherence to dietary provision |
of dietary provision to the same time on the morning following the final day of dietary provision (three days later), in each condition |
|
Secondary |
Change in baroreflex sensitivity |
It has been proposed that low energy availability impairs cardiovascular function and baroreflex sensitivity is a marker of the functionality of the system of cross-talk between cardiac control and blood pressure |
of dietary provision to the same time on the morning following the final day of dietary provision (three days later), in each condition |
|