Evidence regarding the ergogenic effects of caffeine is well-established in young adults, but evidence in older adults remains scarce, particularly during dynamic resistance exercise. Therefore, this study compared the effects of acute caffeine ingestion on upper- and lower-body muscular strength and endurance performance according to age, in young and older adults.

Inclusion Criteria:

• Age between ≥18 and 35 years in young adults and ≥ 55 and 80 years in older adults.
• Body mass index (BMI) lower than 25 kg/m².
• Physically active subjects (≥150 min/week of moderate exercise).
• Healthy men and women without neurological, cardiometabolic, immunological, or physical conditions that prevent them from performing physical exercise.
• Participants capable of performing the tests.

Exclusion Criteria:

• History of neuromuscular, cardiac, or diseases that could affect liver or muscle metabolism.
• Use of drugs or other stimulants that interfere with caffeine intake and intestinal absorption during the tests and study.
• Body mass index (BMI) ≥ 25 kg/m².
• Having undergone prolonged periods of forced physical inactivity during the 6 months prior to the study.
• Performing strenuous exercise within 48 hours prior to the tests.• Failing to replicate the same food intake on the two experimental days.
• Consuming caffeine after 6 PM on the day prior to training or testing.

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