Introduction: Osteoporosis, accidents and subsequent bone fractures cause suffering on an individual level,

as well as an economical burden to the society (Ortiz-Luna et al., 2009; Stevens & Olson, 2000).

It has been estimated that, in Finland alone, between 30,000 to 40,000 osteoporosis-related

fractures occur annually and that 400,000 Finnish people have osteoporosis (Duodecim, 2008).

There are a few potential ways of preventing bone fracture, i.e. strengthening bones and/or

preventing falls (Ortiz-Luna et al., 2009; Stevens & Olson, 2000). In order to withstand

prevalent loading without breaking; while remaining relatively light in weight to allow for

locomotion, bones have the ability to adapt their structure to functional loading (Frost, 2000;

2003; Sievänen, 2005). It has been demonstrated that physical activity affects the weight

bearing skeleton more than the non-weight bearing one (Mikkola et al., 2008), and it may

therefore be argued that, the skeleton is loaded mainly by locomotory actions that impart

strains on bones. Bones are loaded in daily activities by muscles accelerating and decelerating

body segments and resisting the pull of gravity (Burr et al., 1996). Since falling is the single

most significant bone fracture risk factor (Järvinen et al., 2008) and up to 90% of fractures

are caused by falls (Cummings & Melton, 2002; Stevens & Olson, 2000; Wagner et al., 2009),

exercise can be viewed as a potential intervention for fracture prevention. Exercise seemingly

has a potential of both reducing the fall rate and also increasing bone strength. In agreement,

exercise interventions have been shown to successfully decrease the fall rate (Kemmler et al.,

2010; Korpelainen et al., 2006), to strengthen the bones and to decrease the fracture rate (Korpelainen et al., 2006; Sinaki et al., 2002). [Continues, please see the article]