Falls in the aging population are a major public health concern. Outdoor falls in community-dwelling older adults are often triggered by uneven pedestrian walkways. Our understanding of the motor control adaptations to walk over an uneven surface, and the effects of aging on these adaptations is sparse. Here, we study changes in muscle co-contraction, a clinically accepted measure of motor control, due to changes in walking surfaces typically encountered in the outdoor built environment. We address the following research questions: 1) are there walking surface and sex-based differences in muscle co-contractions between young and older adults? and 2) is muscle co-contraction associated with age? We calculated muscle co-contractions from 13 young and 17 older adults during walking at self-selected speeds over even and uneven brick walkways. Muscle co-contraction at the ankle joint was determined from the tibialis anterior and lateral gastrocnemius muscle pair, and at the knee joint from the rectus femoris and semitendinosus muscle pair. Older adults displayed 8–13% greater ankle muscle co-contractions during walking over uneven compared to even surfaces. We found 55–61% (entire gait) and 73–75% (stance phase) greater ankle muscle co-contractions in older females compared to older males during walking over even and uneven surfaces. We found 31–43% greater knee muscle co-contractions in older females compared to older males during the swing phase of walking over even and uneven surfaces. This study underscores the need for determining muscle co-contractions from even and uneven surfaces for quantifying motor control deficits due to aging or neuromuscular disorders.

老龄化人口的下降是一个主要的公共卫生问题。居住在社区的老年人在户外跌倒通常是由不平坦的人行道引发的。我们对在不平坦表面上行走的运动控制适应性的了解，以及老化对这些适应性的影响的理解很少。在这里，我们研究了肌肉共同收缩的变化，这是一种临床上可接受的运动控制措施，由于在室外建筑环境中通常会遇到步行表面的变化。我们解决以下研究问题：1）年轻人和老年人之间的肌肉共同收缩是否存在基于步行表面和性别的差异？2) 肌肉共同收缩与年龄有关吗？我们计算了 13 名年轻人和 17 名老年人在以自行选择的速度在平坦和不平坦的砖砌人行道上行走时的肌肉共同收缩。踝关节的肌肉共同收缩由胫骨前部和腓肠肌外侧肌肉对确定，膝关节由股直肌和半腱肌肌肉对确定。与平坦的表面相比，老年人在不平坦的地面上行走时，踝关节肌肉的共同收缩程度要高 8-13%。我们发现，在平坦和不平坦的表面上行走时，与老年男性相比，老年女性的踝关节肌肉共收缩程度高 55-61%（整个步态）和 73-75%（站立阶段）。我们发现，在行走在平坦和不平坦表面的摆动阶段，老年女性的膝关节肌肉共同收缩比老年男性高 31-43%。这项研究强调需要从平坦和不平坦的表面确定肌肉共同收缩，以量化由于衰老或神经肌肉疾病引起的运动控制缺陷。