Osteoporosis is a systemic bone disorder characterised by a reduced bone mass and structural deterioration, increasing the risk of fragility fractures, particularly in women post-menopause. Bone mass and structure can be assessed by scans.

Antiresorptive medications are commonly prescribed to reduce bone resorption, preventing further bone loss and thus reducing the possibility of fracture. Exercise can also benefit bone mass and structure but current evidence do not show whether exercise is more, or less, effective in combination with antiresorptive medication.

This study will compare the effect of a brief, home-based exercise programme on bone mineral and structural properties in women taking/ not taking antiresorptive medication.

Exercise can benefit bone density and induce structural changes, leading to a decrease in fracture risk. High-impact exercise is often recommended for promoting bone health as it generates the brief, high strains that stimulate bone adaptation. Brief multidirectional hopping exercises have been demonstrated to be a practical and sustainable intervention with older men, pre- and postmenopausal women. They allow exercise to be conducted on one leg, whilst changes in the other leg can be used as a control to compare what would happen without exercise.

The effects of exercise on bone density and structure may be different in women taking osteoporosis medication, but few studies have examined this group. This study thus aims to evaluate the effects of exercise on bone density and structure according to osteoporosis medication use.

The study will be a 12-month long randomised controlled trial including two groups: with and without antiresorptive osteoporosis medication for at least 12 months. Participants must not plan to change their treatment choices during the 12-month study. All participants will complete a 12-month unilateral hopping exercise intervention.

Screening and baseline measurements will include dual X-ray absorptiometry (DXA) and computed tomography (CT) scans of the hip, blood collection, hop assessment and questionnaires. Eligible participants will then be invited to commence the exercise intervention and randomly allocated an exercise leg, with the contralateral leg being untrained to provide a control leg. Randomisation of exercise and control legs will be performed by selecting an opaque sealed envelopes which contain "R" or "L" letters. It is not possible to blind the participant or researchers supervising the intervention to leg allocation.

An initial familiarisation session will be conducted under supervision. The exercise intervention involves a home-based exercise programme starting at three days per week, with the goal of increasing to seven days per week. It will begin with a warm-up targeting the legs and lower back, followed by a progressive exercise regimen that will gradually increase in technique, intensity, and frequency to ensure safety. It will be personalised according to the participants' physical abilities and responses during or after the exercise. Weekly supervised group sessions will be offered, and used to advise participants on progression of exercise. An exercise logbook will monitor adherence. A questionnaire on any injuries, soreness, or discomfort will be administered monthly online or by phone. Participants will be instructed to reduce intensity and frequency or discontinue exercise if they experience any adverse symptoms or discomfort.

Follow-up measurements will be conducted six and twelve months after the start of the exercise intervention is completed. All measurements , except for the CT scan, will also be repeated after six months with each visit expected to last no more than two hours. whereas at twelve months, all measurements will be repeated. CT scans will take place at Glenfield Hospital, Leicester. All other visits will take place at Loughborough University.

Inclusion Criteria:

• Women aged 55-75 years old

• >4y since menopause/hysterectomy/oophorectomy.

• Baseline femoral neck or lumber spine BMD T-score between -1 and -3.

• Able to complete the hopping exercises.

• Have no regular involvement for more than once/week in:

  1. Strength, powerlifting or high load resistance exercise.
  2. High to moderate impact exercise that known to involve ground reaction forces 2 to 4 times greater than body weight (e.g. Jogging).

• Treatment group: taking antiresorptive treatment for osteoporosis continuously for at least 12 months, and who intend to continue this medication for the rest of the study.

• Control group: not taking any medication affecting bone and no intention to commence such medication for the rest of the study.

Exclusion Criteria:

• Body mass index (BMI) >35 kg/m2
• Any medical condition, surgery, or injuries that contraindicate exercises including lower limb or back pain, knee or hip osteoarthritis.
• Vertebral fracture or multiple low trauma fractures (recent expert consensus recommends lower impact exercise for these groups)
• Replacement of hip joint(s)

The researcher conducting imaging assessments and analyses will remain blinded.