The crossover-effect within resistance- and strength training is more or less confirmed with multiple studies showing similar results. The studies shows an increase in muscle strength within the contralateral extremity being exercised. Regarding muscle length or mobility (flexibility) the crossover-effect have not been studied.

For a person to gain an increase in muscle strength mobility training in the form of stretching and flexibility training of our skeletal muscle is a common exercise. However, the evidence are scare and there are only a few studies comparing the effect of prolonged static stretching (> 90 sec) and dynamic flexibility training as to which of these methods has the best length-enhancing effect over time.

The purpose of this study is to compare the crossover-effect of eight weeks of oneleg dynamic flexibility training versus oneleg prolonged static stretching versus a nonstretching controlgroup on mobility in the hamstring muscles in adults with reduced mobility of the hamstring muscle. The aim is also to compare the sustained effect of flexibility training between the two groups, eight weeks after completion of the intervention.

Inclusion Criteria:

• Passiv straigth leg raise < 70 degrees
• Read and understand swedish

Exclusion Criteria:

• Injuries within the hamstrings muscle past 3 month
• Disabilities within the muscloskeletal system (i.e. lower back, thoracic spine, cervikal spine, hip, knee, ankle, fot) affecting the participants life
• Neurological, inflammatoric or heart-diseases
• Nociplasic pain disorders
• Medication with possibility affecting muscle strength of flexibility
• Positive neurodynamic test of the lower extremity

The outcome assessor are not aware of the participants group allocation at time of measurement of outcome measures