Context: Instability resistance training (IRT; unstable surfaces and devices to strengthen the core or trunk muscles) is popular in fitness training facilities.
Objective: To examine contradictory IRT recommendations for health enthusiasts and rehabilitation.
Data sources: A literature search was performed using MEDLINE, SPORT Discus, ScienceDirect, Web of Science, and Google Scholar databases from 1990 to 2012.
Study selection: Databases were searched using key terms, including "balance," "stability," "instability," "resistance training," "core," "trunk," and "functional performance." Additionally, relevant articles were extracted from reference lists.
Data extraction: To be included, research questions addressed the effect of balance or IRT on performance, healthy and active participants, and physiologic or performance outcome measures and had to be published in English in a peer-reviewed journal.
Results: There is a dichotomy of opinions on the effectiveness and application of instability devices and conditions for health and performance training. Balance training without resistance has been shown to improve not only balance but functional performance as well. IRT studies document similar training adaptations as stable resistance training programs with recreationally active individuals. Similar progressions with lower resistance may improve balance and stability, increase core activation, and improve motor control.
Conclusion: IRT is highly recommended for youth, elderly, recreationally active individuals, and highly trained enthusiasts.
Keywords: balance; core training; power; strength training; trunk.