Constant resistant at different speeds while pushing a sled prompts different adaptations in neuromuscular timing on back and lower limb muscles
Resistance training (RT) is commonly used to target specific weakened muscle groups. Among the plethora of methods employed as RT, the current study focused on a sled that provides constant resistance proportional to speed. This study aimed to examine neuromuscular patterns of the lower extremity and trunk muscles in response to pushing a sled with constant resistance at two different speeds. Twenty-six young adults (average age, 23.8) participated in this study. Surface electromyography electrodes were placed on gluteus maximus (GMAX), gluteus medius (GMED), tibialis anterior (TA), gastrocnemius (GA), and erector spinae (lumbar and thoracic) of their dominant leg or side (unilateral at the same side as the dominant lower limb). Neuromuscular timing was collected during four tasks: walking, running, walking-pushing the sled (WP), and running-pushing the sled (RP). All gait activities were repeated twice, with self-selected speed and an equivalent distance of 40 feet. A MANOVA analysis showed that during WP, GMED and GMAX showed more neuromuscular recruitment than leg and trunk muscles when compared to walking. During RP, the thoracic musculature was significantly more involved than any other muscle during running. Based on our findings, we recommend that physiotherapists and trainers use this sled with constant resistance during walking in patients with pelvic or hip weakness. Further, we suggested utilizing the sled in subjects requiring mid-trunk activation at faster speeds, such as fast walking or running.