A review of studies that used B mode ultrasound to estimate age-related changes in anterior thigh skeletal muscle thickness across the adult lifespan

Background: The purpose of this review was to synthesise and determine the age-related change per annum in muscle thickness of the anterior thigh across the adult lifespan. Methods: Electronic databases (PubMed, SPORTDiscus and MEDLINE) were searched for primary studies that were screened for eligibility. Results: Following screening against eligibility criteria, 27 studies were included in the quantitative analysis. Linear regression revealed a 0.02 cm (95 % CI: −0.01, −0.03, p < 0.05) decline in mean muscle thickness per annum from 18 to 80 years of age, a 0.03 cm (95 % CI: −0.01 to −0.05) decline per annum between 20 and 49 years of age and a 0.05 cm (95 % CI: −0.03, −0.07) decline per annum between 50 and 80 years of age. There was a 1.5 cm (t (25) = 6.12, p < 0.05; 95 % CI= 0.98- 1.97 cm) mean difference in muscle thickness between the youngest (18–29yrs: 5.13 cm ± 0.38) and oldest adults (70–80yrs) 3.63 cm ± 0.63). There was no difference in the rate of decline of mean muscle thickness between males (−0.05 cm/annum, 95 % CI= −0.08, −0.02) and females (−0.04 cm/annum, 95 % CI= −0.07, −0.02). There was a larger difference in anterior thigh muscle thickness between the youngest and oldest in females (4.98 cm vs. 3.34 cm, 33 %, p < 0.05) compared with males (5.23 cm vs. 3.98 cm, 24 %, p < 0.05). Conclusion: Mean anterior thigh thickness was estimated to decrease at a rate of 0.02 cm per annum and this rate of decrease was greater after 50 years of age. Females were more susceptible to age-related reductions in anterior thigh muscle thickness than males.