The Effects of Low Energy Availability and High Impact Jumping on Markers of Bone (re)Modelling in Females
The Effects of Low Energy Availability and High Impact Jumping on Markers of Bone (re)Modelling in Females
Osteoporosis is worldwide health epidemic categorized by poor bone health, primarily
 diagnosed by low bone mineral density, and costs healthcare systems billions every year.
 Athletes and exercising people who expend large amounts of energy in physical activity, or
 restrict diet in order to lose weight, are at risk of low energy availability. This is when
 an individual fails to match their exercise energy demand with a appropriate dietary intake
 in order to maintain optimal physiological function; which can lead to low bone mineral
 density, osteoporosis both early and later in life and an increased risk of injury. Runners
 are particularly susceptible to stress fracture in response to low energy availability due to
 repetitive ground impact. Research shows that as little as five days low energy availability
 significantly reduces bone formation, and significantly increases bone resorption, in
 physically active women. The ideal solution is to restore energy availability; however, this
 is often very difficult during periods of intense training and conflicts with the goal of
 weight loss. Therefore, there is a need to develop an alternative tool to protect bone
 health. It is critical that any exercise intervention does not further reduce energy
 availability as previous research shows that this accelerates bone loss rather than prevents
 it. Low repetition high impact jumping exercise is highly beneficial to bone health and has
 been shown to improve bone structure when used as a long-term intervention in energy replete
 states. It takes very little time to complete and uses a very small amount of energy.
 However, no study to date has examined the effects of such an intervention during low energy
 availability. The current study will investigate whether low repetition high impact jumping
 prevents or reduces the reduction in bone formation and the increase in bone resorption
 experienced during five days of low energy availability and findings will have implications
 on athletic and recreational training recommendations in order to protect bone health.
Participants will complete two four-day experimental conditions within the first seven days
 of two separate menstrual cycles. These will be preceded by a four-day baseline assessment
 period. There are three experimental conditions in total: control (CON), low energy
 availability (LEA) and low energy availability and high impact jumping (LEA+J). Participants
 will be randomly allocated to complete the control condition and either the LEA or LEA+J
 condition. The order in which the two conditions are completed will be randomized and
 counterbalanced. In total, fifteen laboratory visits will be required per participant:

 Baseline assessment (four days and one visit):

 Visit 1:

 Participants will come to the laboratory to complete the informed consent procedure on day 1,
 once they have had at least 24 hours to consider the participant information sheet. Providing
 informed consent is given, participants will complete three questionnaires (a health screen,
 the Low Energy Availability in Females Questionnaire and the International Physical Activity
 Questionnaire) which include questions regarding their medical and injury history, dietary
 habits, menstrual cycle and physical activity habits. They will then have their height and
 weight taken. Provided the responses and measures confirm that the participant meets the
 inclusion and exclusion criteria, they will then undergo familiarization of resting metabolic
 rate assessment where they will lay supine in a dimly lit room whilst expired gas is
 collected via a mouthpiece. During familiarization the researcher will check for signs of
 hyperventilation. Following that, the participants will be familiarized with a jumping
 exercise routine if the participant is randomized into the group that will be performing this
 routine during an experimental condition. Finally, the participant will be asked to complete
 an incremental exercise test to volitional exhaustion on a treadmill whilst expired gas is
 collected and analysed using a metabolic cart, and heart rate and rating of perceived
 exertion are taken, as a measure of aerobic fitness.

 For the following three days (2, 3 and 4), participants will be instructed to self-report
 weighed energy intake using a set of scales provided and a food diary according to the
 instructions on the diary itself which the researcher will read through with the participant.
 They will be asked to eat according to their usual dietary habits and return it
 electronically at the end of day 4, or during a subsequent visit. Participants will also be
 provided with a tri-axial accelerometer (Actigraph GT3X+) device and instructed to wear it
 around the waist for the entirety of days 2, 3 or 4 (apart from when bathing and washing).
 They will be not required to visit the laboratory on days 2, 3 or 4.

 Experimental conditions (four days and four visits, per condition):

 The following will outline the experimental protocol assuming the participant is completing
 the LEA+J condition followed by the CON condition, and end with a description of how the
 protocol differs should they be randomly allocated to complete the LEA condition as opposed
 to the LEA+J, condition. Participants will be required to refrain from exercise which is not
 part of the study for the entirety of all experimental conditions.

 LEA+J condition:

 Participants will be required to notify the research team at the onset of their next menses
 and will commence the experimental condition the following day, or the day after that if the
 participant is not able to do what is required of them the following day. From the first
 until the last day of each condition, participants will be required to wear the Actigraph
 device at all times apart from when bathing and washing. Participants will be instructed to
 record their diet during day 1, as they did during days 2, 3 and 4 of the baseline condition,
 and will be asked to eat according to their usual dietary habits but instructed to make
 choices that they will be able to replicate ahead of each subsequent experimental condition.
 They will not be permitted to drink caffeine or alcohol.

 Visit 1:

 Participants will be required to collect their final meal on day 1 from the laboratory and
 will be instructed to eat it at exactly 20:00. They will complete the Pittsburgh Sleep
 Quality Index (PSQI; a questionnaire regarding sleep habits and quality during the last
 month). They will also be instructed to refrain from any other food or drink, other than
 water, for the rest of the evening. Participants will be provided with a self-report water
 intake record sheet and water bottle from which to drink and instructed to report daily water
 intake from the start of day 2 until the end of the condition. They will also be provided
 with a small container suitable to collect a urine sample upon waking the following morning.
 Participants will be instructed to bring the sample with them to the laboratory, where it
 will be analysed and disposed of immediately.

 Visit 2:

 On day 2 of the first condition, participants will be required to arrive at the laboratory
 between 06:00-09:00 without eating breakfast or ingesting caffeine for at least 18 hours
 prior. The participant will be asked to travel by car or by public transport and restrict
 walking distance as much as possible. Weight and body composition will be taken in shorts and
 underwear using scales and bio-electrical impedance. The investigators will then perform a
 resting metabolic rate assessment and a series of cardiovascular measures using pressure
 cuffs, tonometry and electrocardiography. A venous blood sample will be split into plasma and
 serum separation Vacutainers from the arm by a phlebotomy trained researcher using standard
 venepuncture methods. The participants will then be instructed to complete a brief high
 impact jumping exercise routine on a Kistler force platform with demonstrations by the
 researcher and continued feedback to maintain optimum form. All jumps will be performed
 barefoot. The investigators will then provide a breakfast to consume in the laboratory along
 with a multivitamin multi-mineral tablet. The food the participants are required to eat for
 the rest of the day will be packed into a cool box to take away and the participants will not
 be permitted to consume anything which is not provided within the cool box, other than
 "calorie-free" drinks (black coffee, black tea, green tea, etc.). The participants will be
 instructed to perform a similar jump routine at home at least 8 hours after the morning jump
 routine. All jumps will be performed barefoot.

 Visits 3 and 4:

 On days 3 and 4, participants will be required to arrive at the laboratory between
 06:00-09:00 without eating breakfast. Participants will return any uneaten food from the
 previous day and report any items consumed (other than "calorie-free" drinks) that were not
 part of the cool box provided. The participants will complete the morning jump routine and
 have their prescribed breakfast with multivitamin and multi-mineral tablet at the laboratory,
 before leaving with the rest of their food for that day packed in a cool box. The
 participants will not be permitted to consume anything which is not provided within the cool
 box, other than "calorie-free" drinks. The participants will be instructed to complete the
 evening jump routine - as on day 2.

 During day 4, participants will only be permitted to drink water and will be instructed to
 consume their final meal at 20:00 and refrain from any other food or drink (other than water)
 for the rest of the evening. At the end of day 6, the participants will also be provided with
 a small container suitable to collect a urine sample upon waking the following morning.
 Participants will be instructed to bring the sample with them to the laboratory, where it
 will be analysed and disposed of immediately.

 Visit 5:

 On day 5, participants will repeat the same process as on day 2, except will be required to
 arrive at the laboratory at the exact same time rather than anywhere between 06:00 - 09:00
 and they will not complete the morning or evening jump routines, the PSQI or be given
 breakfast, a multivitamin multi-mineral tablet nor food to take away.

 Participants will be provided with an ovulatory test kit to take away and use once per day
 (urinate on a stick as per a pregnancy test) for up to 8 days in the middle of the menstrual
 cycle. Once a positive test is observed the participants will report this to the research
 team and if no positive is reported within 8 days this will also be reported to the research
 team.

 CON condition:

 Visits 1-5:

 Participants will again be required to notify the research team at the onset of the next
 menses (following the end of the LEA+J condition) and will commence the CON condition the
 following day, or the day after that if the participant is not able to do what is required of
 them the following day. The same procedure as in the LEA+J condition will be repeated,
 however, rather than recording their diet during day 1, participants will be instructed to
 repeat what was previously recorded. Also, the total energy intake in the food provided in
 the LEA+J condition will be a third of that provided in the CON condition and participants
 will not take a multivitamin multi-mineral tablet or be required to perform morning or
 evening jump routines.

 How will the protocol differ for participants completing the LEA condition?

 The procedure for the LEA condition is the same as in the LEA+J condition, however,
 participants will not be required to perform morning or evening jump routines.
To take part in this study, the following inclusion criteria must be met:

 -  Menstrual cycles that are between 21 - 35 days in length for at least the previous
 three cycles

 -  Regular length of menstrual cycle (less than six days difference between cycles) for
 at least the previous three cycles

 -  Body mass index between 18.5 - 30 kg.m squared

 -  Weight stable for the past three months and not currently dieting

 Participants will not be able to take part in this study if any of the following exclusion
 criteria are met:

 -  Smoker

 -  Pregnant

 -  Vegan

 -  Have used hormonal contraception at any point within the previous three months

 -  Regularly engage in >3 vigorous, or >5 moderate, exercise sessions a week

 -  Compete regularly in a high or multi-directional impact sport at national level or
 higher

 -  Have sustained a bone injury within the previous twelve months

 -  Have sustained any injury within the past six months that restricted their ability to
 exercise

 -  Taken hormone replacement therapy (HRT) at any point during the past three months

 -  Have been previously diagnosed with an eating disorder

 -  Have taken any medications (other than vitamin or mineral supplements) known to effect
 bone metabolism within the previous three months (e.g. glucocorticoids,
 anticonvulsants or anabolic steroids)

 -  Have previously been diagnosed with a medical condition known to impact bone health
 (e.g. hypothyroidism, hyperthyroidism, diabetes mellitus, hypercortisolism and renal
 or gastrointestinal disease)

 -  Have previously been diagnosed with a pathology known to impact menstrual function
 (e.g. primary ovarian insufficiency, hyperprolactinemia, thyroid dysfunction,
 polycystic ovarian syndrome and any other conditions of androgen excess)