Correction: Portable automated rapid testing for auditory assessment: repeated at-home testing in older adults.

Sarcopenia, defined as the progressive loss of skeletal muscle mass and strength, is a growing public health concern in ageing populations. Consensus groups, including the Global Leadership Initiative on Sarcopenia (GLIS) and the European Working Group on Sarcopenia in Older People (EWGSOP2), advocate for early identification and the implementation of preventive strategies to mitigate the socio-economic and health burdens associated with sarcopenia. Greater dietary protein intake and higher levels of physical activity are key modifiable factors that support muscle health and have been proposed both for its prevention and its treatment. Studies have shown that protein intakes exceeding the RDA (0.8 g/kg/ideal body weight) are associated with greater appendicular lean soft tissue (ALST), reflective of muscle mass. Yet, most US adults do not meet these thresholds. Resistance exercise is the most effective stimulus for muscle protein synthesis, particularly when combined with a high-protein diet. Research has also shown that aerobic exercise has a significant impact on improving muscle structure and hypertrophy in older adults, together with improved cardiorespiratory fitness. While intervention studies support the synergistic effects of protein supplementation and resistance exercise on muscle outcomes, there is growing interest in whether similar benefits may be observed in community settings, particularly when individuals meet the WHO’s recommended aerobic physical activity guidelines (150–300 min/week moderate or 75 min/week vigorous activity), along with muscle-strengthening activities at least twice a week to further support skeletal muscle mass and function. The fifth decade of life represents a critical window for the prevention of sarcopenia, as this period coincides with the onset of decline in muscle quality and neuromuscular integrity. Anabolic resistance, which is defined as the impaired muscle responses to anabolic stimuli, has been shown to become more pronounced with age, highlighting the need for early intervention. ALST and handgrip strength (HGS) have been identified as reliable markers of muscle mass and upper body strength, respectively. These are linked to frailty, mobility, and mortality risk. However, epidemiological evidence about the impact of vigorous physical activity and protein intake on outcomes typical of sarcopenia is still limited. This study aimed to investigate whether meeting WHO physical activity guidelines, particularly vigorous activity, combined with higher protein intake, is associated with greater ALST and HGS in US adults aged 40–59 years.