Effects of HIIT in Older Adults

This randomized controlled study aimed to evaluate the effectiveness of a high-intensity interval training (HIIT) protocol on functional fitness in community-dwelling older adults. With the global rise in life expectancy and the associated functional decline in aging populations, there is an increasing demand for time-efficient, evidence-based interventions that can promote physical independence and healthy aging.

Participants aged 60 years or older were recruited and assigned to either a HIIT intervention group or a control group. The HIIT group engaged in supervised training sessions three times per week. Each session included a warm-up, a core HIIT segment with short bursts of high-intensity movements interspersed with active recovery, followed by a cool-down. Exercises were adapted to be safe and appropriate for older adults, focusing on full-body functional movements and performed in a group setting under professional supervision.

Functional fitness was evaluated using the Senior Fitness Test battery and handgrip strength testing. This included assessments of:

• Lower body strength (30-second chair stand)
• Upper body strength (arm curl test)
• Lower body flexibility (chair sit-and-reach)
• Upper body flexibility (back scratch test)
• Agility and dynamic balance (Timed Up and Go test)
• Cardiorespiratory endurance (2-minute step test)
• Handgrip strength (digital dynamometer, dominant hand)

Measurements were taken at three time points: pre-intervention (M1), midpoint (M2), and post-intervention (M3). Statistical analysis included nonparametric ANOVA-type models (Brunner-Langer), given the non-normal distribution of many outcome variables.

The results indicated statistically significant improvements in the HIIT group for several domains of functional fitness compared to the control group. Notably, participants in the HIIT group showed:

• Increased handgrip strength
• Improved upper and lower limb flexibility
• Enhanced aerobic endurance
• Improved mobility and agility (TUG test)
• Increased upper body strength (arm curl)

These results support the effectiveness of HIIT in improving multiple aspects of physical function among older adults, without the need for resistance machines or prolonged exercise sessions. The findings highlight the feasibility and clinical relevance of using HIIT as a tool to enhance physical independence, prevent disability, and reduce the burden on health systems.

All procedures were approved by the Ethics Committee of the Polytechnic Institute of Bragança and followed international guidelines (SPIRIT, CONSORT, Declaration of Helsinki). Participation was voluntary, and informed consent was obtained from all individuals.

Inclusion criteria

• Community-dwelling individuals aged 60 years or older
• Able to walk independently without assistive devices
• Sufficient cognitive ability to follow instructions and participate in assessments
• Medically stable and cleared for physical activity by a healthcare provider
• No current participation in structured exercise programs
• Willingness to participate in the intervention and attend scheduled assessments
• Provided written informed consent

Exclusion criteria

• Individuals younger than 60 years
• Severe musculoskeletal, cardiovascular, or neurological conditions that contraindicate physical exercise
• Uncontrolled hypertension or diabetes
• Recent surgery or hospitalization in the past 6 months
• Severe visual or auditory impairments that limit test performance
• Use of mobility aids (e.g., walker or cane for ambulation)
• Participation in another clinical trial simultaneously