The aim of this study is to build on previous published work, which has indicated lumbar mobilisations have the ability to increase hamstring extensibility and decrease muscle activity. The primary aim of this project is investigate if lumbar mobilisations have an affect on the Nordic Hamstring exercise.

Aim: To investigate the short-term effects L4 and L5 Unilateral Posterior Anterior (UPA) Mobilisations on the lumbar spine on the Nordic Hamstring Exercise. Measures will include hamstring peak torque, sEMG activity and knee angle at first rapid change in angular acceleration.

The study aims to investigate the short-term effects L4 and L5 Unilateral Posterior Anterior (UPA) Mobilisations on the lumbar spine on the Nordic Hamstring Exercise. Measures will include hamstring peak torque, sEMG activity and knee angle at first rapid change in angular acceleration.

Recruitment will take place via flyer and email. All testing will take place in the biodex laboratory at Teesside University. Due to the nature of the cross-over design participants will attend the laboratory six times, two for familiarisation sessions, and a remaining four testing session all 72 hours apart. The four testing sessions will contain two control and two intervention sessions attended in a randomised order.

Following recruitment participants will be required to complete a medical questionnaire and sign a consent form following reading the participant information sheet.

The Nordic Hamstring exercise will be performed by each participant across the intervention and control conditions. Participants will watch a video of a subject completing the Nordic exercise program. They will also receive the following verbal instructions:

'Players start in a kneeling position, with the torso from the knees upward held rigid and straight. The training partner ensures that the player's feet are in contact with the ground throughout the exercise by applying pressure to the player's heels/lower legs. The player then lowers his upper body to the ground, as slowly as possible to maximize loading in the eccentric phase. Hands and arms are used to break his forward fall and to push him back up after the chest has touched the ground, to minimize loading in the concentric phase (Mjølsne et al, 2005; Petersen et al, 2011).

All participants will be given the opportunity to ask questions as necessary.

A standardised warm-up on an ergometer will be undertaken for 5 minutes at 60% max resting heart rate.

Following the warm-up all participants will familiarise themselves with the Nordic Hamstring Exercise on the hamstring solo equipment. They will be able to practice up to 8 repetitions. This data will be used for a reliability study to understand the number of required repetitions for the main study.

During testing participants will attend the same laboratory for the remaining four testing sessions. They will receive two intervention sessions, when the lumbar mobilisations will be performed, and two when the control is administered.

The same warm-up undertaken during the familiarisation session will be undertaken prior to testing.

The intervention will consist of unilateral lumbar mobilisations at the L4 and L5 level in a Posterior Anterior direction. The side of the mobilisation will be determined by dominate leg - considered the kicking foot. The mobilisations will be administered by a physiotherapist with at least 12 years clinical experience. Teksan grip sensors will be worn by the physiotherapist to calculate the force applied to the participant. Grade three mobilisations will be applied for a one minute period three times at both L4 and L5 level.

For the control, all participants will be laid prone on the medical plinth in the same position will no mobilisations administered.

Outcome measures will include collection of hamstring peak force data, sEMG of the Biceps Femoris, 3D Motion capture data and subjective likert scale of exercise difficulty.

Inclusion Criteria:

Current Teesside University Students/Staff 18+ years Engaged in Football related activity once a week Provide Informed Consent No current musculoskeletal Injury

Exclusion Criteria:

Current symptomatic low back pain or lower limb pathology including any injuries to the lower limb/lumbar spine within the last 6 months Previous ACL/Hamstring Rupture tear or diagnosed anterior knee pain. Under supervision of another health clinician Medical questionnaire not completed Red flags on medical questionnaire Any neurological problems Contraindications or precautions to spinal mobilisation

• malignancy, inflammatory or infectious processes involving the spine or peripheral joints,
• osteoporosis,
• spinal disorders including spondylolisthesis, ankylosing spondylitis, spinal fusion