Journal of Aging and Physical Activity, 2014, 22, 490-498 http://dx.doi.Org/10.1123/JAPA.2013-0108 ©2014 Human Kinetics, Inc. Relationships Between Trunk Muscle Strength, Spinal Mobility, and Balance Performance in Older Adults Urs Granacher, Andre Lacroix, Katrin Roettger, Albert Gollhofer, and Thomas Muehlbauer This study investigated associations between variables of trunk muscle strength (TMS), spinal mobility, and balance in seniors. Thirty-four seniors (sex: 18 female, 16 male; age: 70 + 4 years; activity level: 13 + 7 hr/week) were tested for maximal isometric strength (MIS) of the trunk extensors, flexors, lateral flexors, rotators, spinal mobility, and steady-state, reactive, and proactive balance. Significant correlations were detected between all measures of TMS and static steady-state balance (r = .43-57, p < .05). Significant correlations were observed between specific measures of TMS and dynamic steady-state balance (r = .42-55, p < .05). No significant correlations were found between all variables of TMS and reactive/proactive balance and between all variables of spinal mobility and balance. Regression analyses revealed that TMS explains between 1-33% of total variance of the respective balance parameters. Findings indicate that TMS is related to measures of steady-state balance which may imply that TMS promoting exercises should be integrated in strength training for seniors. Keywords: elderly, core, gait, postural balance, force, physical performance The aging process is frequently characterized by a flexed (i.e., hyperkyphotic) posture (Balzini et al„ 2003) and/or an impaired spinal mobility (Hamalainen, Suni, Pasanen, Malmberg, & Miilun- palo, 2006), resulting in diminished mobility in older adults (Ryan & Fried, 1997). This is, among others, caused by an age-related loss in trunk muscle strength (TMS) and mass. In fact, older men aged 71-75 years showed 35% and 45% lower maximal isometric trunk flexion and extension strength compared with a group of 31 -35 year old men (Viitasalo, Era, Leskinen, & Heikkinen, 1985). Further, Abe et al. (2011) observed a gradual decrease in trunk muscle mass in men and women aged 20-95 years. In addition, Kasukawa et al. (2010) were able to show that back extensor strength, lumbar kypho- sis, mobility of the lumbar spine, and mobility of spinal inclination were significantly associated with the presence or absence of falls in elderly individuals aged 60-97 years. Based on the findings of these cross-sectional studies, it appears that TMS is associated with spinal kyphosis as well as spinal mobility and thus, may modulate balance, mobility, and falls. However, findings from a recently published systematic litera- ture review on potential associations between variables of TMS, trunk muscle composition, balance, functional performance, and falls in older adults revealed only small to medium correlations (Granacher, Gollhofer, Hortobagyi, Kressig, & Muehlbauer, 2013). It should be noted though that the authors classified their results as preliminary, given that only six studies were found and included in their review. Of the six studies, three studies investigated older adults who suffered from chronic diseases (e.g., osteoporosis, back pain; Hicks et al., 2005a, 2005b; Pfeifer et al., 2001). Two studies examined mobility impaired seniors (e.g., had a history of falls; Kasukawa et al., 2010; Suri, Kiely, Leveille, Frontera, & Bean, Granacher, Lacroix, and Muehlbauer are with the Division of Training and Movement Sciences, Cluster of Excellency in Cognition Sciences, Univer- sity of Potsdam, Potsdam, Germany. Roettger and Gollhofer are with the Institute of Sport and Sport Science, Albert-Ludwigs-University Freiburg, Freiburg, Germany. Address author correspondence to Urs Granacher at urs.granacher@uni-potsdam.de. 2009). In addition, the applied testing methodology varied largely between the six studies. For instance, TMS was assessed using repetition maximum tests on customized trunk resistance training machines (Suri et al., 2009), instrumented apparatus (e.g., isokinetic dynamometer, strain/pressure/force-gauge dynamometer/manual tester; Kasukawa et al., 2010; Pfeifer et al., 2001), and clinical tests (e.g., McGill’s trunk extensor/flexor endurance test; Suri et al., 2009). Two studies investigated trunk muscle composition (i.e., muscle area/attenuation) using computerized tomography (Hicks et al., 2005a, 2005b). Tests of balance and functional performance comprised static balance tests (e.g., postural sway during one- legged stance; Kasukawa et al., 2010; Pfeifer et al., 2001; Suri et al., 2009), balance test batteries (e.g., Berg balance scale; Suri et al., 2009), and physical performance batteries (e.g., Health ABC physical performance battery; Hicks et al., 2005a, 2005b). Two studies determined rate of falls retrospectively (Kasukawa et al., 2010; Pfeifer et al., 2001). Moreover, there was substantial variability in test modality (e.g., number of practice and/or test trials). Thus, the included studies were heterogeneous in terms of the investigated subjects and the applied testing methodology. Based on these preliminary findings in the literature, additional well-designed correlative analyses are needed that investigate the relationship between measures of TMS, balance, and functional performance in old age. Further, no study has been conducted yet that investigated associations between spinal mobility and balance as well as functional performance in seniors. Knowledge regarding potential relationships between variables of TMS, spinal mobility, and balance, as well as functional performance may help to develop specifically tailored intervention programs that have the potential to improve balance and functional performance in older adults by ultimately reducing the number of falls. Thus, the aim of this study was to investigate associations between measures of TMS and spinal mobility, as well as steady- state (i.e., maintaining a steady position in sitting, standing, and walking), reactive (i.e., compensation of a disturbance), and proac- tive (i.e., anticipation of a predicted disturbance) balance in older adults. It is hypothesized that both TMS and spinal mobility are related to measures of steady-state, reactive, and proactive balance. 490