Muscle atrophy and weakness accompanying aging contributes greatly to an increased risk and incidence of falling. Over one-third of individuals 65 years of age or older experience a fall \[1,2\]. In a 2006 review \[3\] of 16 controlled (prospective and retrospective) studies \[4-8\] major factors affecting risk were identified with the most influential risk factors being muscle weakness, and deficits in balance and gait. The rate of muscle de-conditioning is accelerated by inactivity, muscle disuse and co-morbid conditions \[9-12\]. Older individuals with deficits in muscle size, strength and power can become so mobility-limited that simply walking to the mailbox is at the upper limit of their physical capacity \[9\] Hence, improving the muscle conditioning of an elderly individual with high fall risk may decrease the risk and incidence of falls \[13-18\]. Muscle conditioning often requires considerable effort, yet many elderly individuals lack the energetic reserves required for high-intensity exercise. Consequently, both elderly women and men are caught in a "downward-spiral" as their muscle de-conditioning accelerates the myriad risks of falling and the incidence of life-threatening falls.
We have explored the safety and feasibility of a high-intensity Resistance Exercise via Negative, Eccentrically-induced Work (RENEW) in multiple groups of de-conditioned elderly males and females, many characterized as being at-risk for a fall due to their impaired muscle condition, balance, mobility and confidence. Compared to traditional resistance exercise (TRAD), RENEW is novel and advantageous in that RENEW: is a high-intensity exercise for muscle, yet requires little effort (resulting in high levels of adherence); induces unprecedented muscle conditioning (size, strength and power); and lowers falling risks (balance, mobility and confidence) \[19-23\]. This study is unique and timely because it is unknown if RENEW's amplified muscle conditioning translates to a decreased incidence of falls, particularly for those at the highest risk for an injurious fall, i.e. those who have fallen. Further, RENEW's long-term sustainability has not been explored.
This clinical trial will compare the effects of RENEW vs. TRAD as part of a multi-component exercise and fall-reduction program (MCEFRP) on muscle conditioning (muscle size, strength, power); falling risks (balance, mobility and confidence); as well as the fall incidence. We anticipate that muscle conditioning will mediate the effect of RENEW on falling risks and fall incidence. As well, the sustained benefit of RENEW will be explored.
Objective #1: Test whether RENEW's effect is different than TRAD's effect on muscle conditioning, i.e., muscle size, strength and power.
• H1a: RENEW will result in greater increases (relative to TRAD) in whole muscle volume, isometric strength and concentric power of the leg extensor muscles, specifically the quadriceps.
Objective #2: Test whether the effects of RENEW on falling risks is mediated by muscle conditioning.
* H2a: RENEW will decrease falling risks (impaired balance, mobility and confidence) more than TRAD.
* H2b: RENEW's effects on falling risks will be mediated by greater muscle conditioning.
Objective #3: Determine if RENEW lowers fall incidence more than TRAD.
• H3a: The RENEW intervention will result in a lower fall incidence (falls and near falls) than TRAD via the direct influence on muscle conditioning and via the indirect influence of decreasing falling risks.
