Can regular walking improve older adults' muscle strength without increasing lean mass?

Details

Sarcopenia—the age-associated involuntary loss of muscle and strength—can progress to clinically relevant functional decline. Resistance exercise reduces muscle and strength loss, but may not be feasible for some older adults. Aerobic exercise training (AET) improves cardiopulmonary health, but its effects on protein turnover, muscle mass, and strength are less clear.

The researchers aimed to determine whether AET improves basal myofibrillar protein synthesis (MPS) and capillarization, promoting muscle hypertrophy and strength. They hypothesized that AET would improve strength alongside increases in MPS and capillarization.

In this randomized intervention study, older adults were assigned to a non-exercise group (NON; n = 11, age 71.4 ± 4.18 years) or an exercise group (EX; n = 12, age 73.7 ± 4.05 years). EX completed 24 weeks of AET: walking three times per week for 45 minutes at 70% of heart rate reserve. NON remained sedentary.

A stable isotope tracer was infused. MPS and capillarization were analyzed using vastus lateralis muscle biopsies. Strength was measured using isokinetic dynamometry, and lean mass was determined using dual-energy X-ray absorptiometry.

In EX, basal MPS increased by 50.7% (P = 0.01), capillary density by 66.4% (P = 0.03), peak oxygen consumption by 15.8% (P = 0.01), and quadriceps strength by 15.1% (P = 0.01). Muscle quality, defined as peak torque divided by leg lean mass, increased by 15.5% (P = 0.01). Lean mass did not change significantly (P > 0.05).

The researchers concluded that AET increases muscle protein turnover and capillarization in older adults, improving muscle quality.