Is the plank exercise suitable for Everyone? An electromyographic comparison between trained and untrained individuals

Objectives: The plank is one of the most used exercises for core strengthening however, no prior research examined performance between trained and untrained individuals. Thirty healthy subjects were divided on their training background: 15 trained (mean age: 23.2 ± 1.78 years) and 15 untrained (mean age: 24.86 ± 2.99 years). All participants performed an isometric plank held until voluntary muscle failure. Muscle activation was monitored across seven primary muscle groups involved in plank execution: rectus abdominis, external oblique, internal oblique, erector spinae, gluteus maximus, gluteus medius, and multifidus. The normalized root means square EMG activity for each muscle was recorded throughout the exercise and divided into three distinct phases preceding exercise failure. Results: MANOVA showed significant differences between groups in muscle activation during full movement analysis for erector spinae (p = 0.024) and multifidus (p = 0.027) with greater activity in the untrained group compared to the trained group. Untrained individuals showed greater multifidus activation in the early and middle phases and higher erector spinae activation across all exercise phases (p < 0.05). Conclusion: These findings indicate that the plank is not universally suitable across training levels, emphasizing the need for individualized core exercise selection based on training experience.