The Role of Instability With Resistance Training

Abstract

There are many instances in daily life and sport in which force must be exerted when an individual performing the task is in an unstable condition. Instability can decrease the externally-measured force output of a muscle while maintaining high muscle activation. The high muscle activation of limbs and trunk when unstable can be attributed to the increased stabilization functions. The increased stress associated with instability has been postulated to promote greater neuromuscular adaptations, such as decreased cocontractions, improved coordination, and confidence in performing a skill. In addition, high muscle activation with less stress on joints and muscles could also be beneficial for general musculoskeletal health and rehabilitation. However, the lower force output may be detrimental to absolute strength gains when resistance training. Furthermore, other studies have reported increased cocontractions with unstable training. The positive effects of instability resistance training on sports performance have yet to be quantified. The examination of the literature suggests that when implementing a resistance training program for musculoskeletal health or rehabilitation, both stable and unstable exercises should be included to ensure an emphasis on both higher force (stable) and balance (unstable) stressors to the neuromuscular system.

Influence of Leg Dominance on Single-Leg Stance Performance During Dynamic Conditions: An Investigation into the Validity of Symmetry Hypothesis for Dynamic Postural Control in Healthy Individuals

“…Unlike quiet standing conditions, most of the daily life activities are performed in constantly changing environmental contexts and require instant biomechanical adaptations. Dynamic balance tasks, therefore, have been increasingly recommended recently to monitor functional recovery after injury, since they are believed to reflect the underlying mechanism of postural control strategies utilized in daily life activities (15,16). Hatzitaki et al (17), for example, have shown that balance performance under quiet standing tasks is mostly related to perceiving and processing visual inputs, whereas maintaining balance under dynamically demanding tasks depends highly on rapid processing of somatosensory afferences and initiation of corrective motor responses.…”

Sex Differences in the Cross-sectional Areas of Psoas Major and Thigh Muscles in High School Track and Field Athletes and Nonathletes

“…For adolescent boys and girls, however, relatively little information on the extent of sex differences in the muscularity of the trunk is available. Trunk muscles have a critical role in the maintenance of stability and balance when performing movements with the extremities (Andersen et al, 1988), and a strong and stable trunk provides a solid foundation for the torques generated by the limbs (Behm and Anderson, 2006;Kibler et al, 2006). Among the muscle groups located in the trunk, the psoas major is the only muscle that connects the lumber spine and lower limbs (Arbanas et al, 2009) and the largest in cross-section at L4-L5 (McGill et al, 1993;Santaguida and McGill, 1995).…”

Concurrent and Criterion-Referenced Validity of Trunk Muscular Fitness Tests in School-Aged Children

“…These results provide preliminary evidence of the concurrent and criterion-referenced validity of the overall core measures, suggesting that if health-related cut-points were to be developed for the muscular fitness test scores, the low back criterion and overall core measures would produce similar classification of students into a three Fitness Zone classification scheme. From a health-related perspective and assuming LBP is related to low back and core muscular endurance (Balague, Troussier, & Salminen, 1999;Behm & Anderson, 2006), this approach is useful since it can provide insights on the ability of field tests to classify children who are at risk for developing LBP based on testing performance. Incorporating these assessments into physical education will also increase the value of the lesson if physical educators communicate the importance of low back health while concomitantly allowing the students to perform movements that will strengthen the musculature of the low back.…”