Nowadays, ageing is an important aspect to consider from a social, healthcare and economic perspective. For this reason, it is necessary to focus on all the elements which can help staying healthy and active in old age. Physical activity and exercise are one of these, and more specifically resistance training.

Recently, it is been evidenced that physical activity and exercise are an important coping strategy to get what is called "active ageing". However, it is still under discussion some key aspect, like the training type or the optimal dose, among others. There is a modality of resistance training which it has not been sufficiently studied in old age population: the high intensity interval training. It has been demonstrated in other population (like cardiovascular patients or cancer survivor patients) that this modality of training can improve a lots their physical condition. Furthermore, it produces a higher adhesion to the training program, because it does not require so long time like another type of training. For this reason, the aim of this investigation is to assess how implement this modality of training on elderly people with sarcopenia.

Inclusion Criteria:

• Older adults aged 55 years or older.
• Living in an institutionalised setting or community-dwelling older adults living in the province of Badajoz or Cáceres.
• Voluntarily participating in the study.
• Who had a diagnosis of sarcopenia/fragility in the last year.
• Submit a prescription from the centre's medical practitioner to participate in the study as physiotherapy intervention would be appropriate and potentially beneficial.

Exclusion Criteria:

• Patients with cognitive impairment (score ≥24 in the validated Spanish version for general older adults of the Mini-Mental Status Examination).
• Unable to tolerate moderate physical activity due to cardiovascular or respiratory disease.
• With balance disorders other than those caused by ageing such as dizziness or vestibular disorders requiring the ingestion of medication with a potential effect on balance, as well as balance disorders secondary to the ingestion of any medication or other medical causes.
• At high risk of falling (≥ 51 points on the MORSE scale).
• At high risk of falling (≥ 51 points on the MORSE scale).
• At high risk of falling (≥ 51 points on the MORSE scale).