@article{MuehlbauerGranacherBordeetal.2017,
  author    = {Muehlbauer, Thomas and Granacher, Urs and Borde, Ron and Hortobagyi, Tibor},
  title     = {Non-Discriminant Relationships between Leg Muscle Strength, Mass and Gait Performance in Healthy Young and Old Adults},
  series = {Gerontology},
  volume    = {64},
  journal   = {Gerontology},
  number    = {1},
  publisher = {Karger},
  address   = {Basel},
  issn      = {0304-324X},
  doi       = {10.1159/000480150},
  pages     = {11 -- 18},
  year      = {2017},
  abstract  = {Background: Gait speed declines with increasing age, but it is unclear if gait speed preferentially correlates with leg muscle strength or mass. Objective: We determined the relationship between gait speed and (1) leg muscle strength measured at 3 lower extremity joints and (2) leg lean tissue mass (LTM) in healthy young (age: 25 years, n = 20) and old (age: 70 years, n = 20) adults. Methods: Subjects were tested for maximal isokinetic hip, knee, and ankle extension torque, leg LTM by bioimpedance, and gait performance (i.e., gait speed, stride length) at preferred and maximal gait speeds. Results: We found no evidence for a preferential relationship between gait performance and leg muscle strength compared with gait performance and leg LTM in healthy young and old adults. In old adults, hip extensor strength only predicted habitual gait speed (R-2 = 0.29, p = 0.015), whereas ankle plantarflexion strength only predicted maximal gait speed and stride length (both R-2 = 0.40, p = 0.003). Conclusions: Gait speed did not preferentially correlate with leg muscle strength or leg LTM, favoring neither outcome for predicting mobility. Thus, we recommend that both leg muscle strength and leg LTM should be tested and trained complementarily. Further, hip and ankle extension torque predicted gait performance, and thus we recommend to test and train healthy old adults by functional integrated multiarticular rather than monoarticular lower extremity strength exercises.},
  language  = {en}
}
@article{BeijersbergenGranacherGaebleretal.2017,
  author    = {Beijersbergen, Chantal M. I. and Granacher, Urs and Gaebler, Martijn and DeVita, Paul and Hortobagyi, Tibor},
  title     = {Hip mechanics underlie lower extremity power training-induced increase in old adults' fast gait velocity},
  series = {Gait \& posture},
  volume    = {52},
  journal   = {Gait \& posture},
  publisher = {Elsevier},
  address   = {Clare},
  issn      = {0966-6362},
  doi       = {10.1016/j.gaitpost.2016.12.024},
  pages     = {338 -- 344},
  year      = {2017},
  abstract  = {Methods: As part of the Potsdam Gait Study (POGS), healthy old adults completed a no-intervention control period (69.1 +/- 4A yrs, n =14) or a power training program followed by detraining (72.9 +/- 5.4 yrs, n = 15).We measured isokinetic knee extensor and plantarflexor power and measured hip, knee and ankle kinetics at habitual, fast and standardized walking speeds. Results: Power training significantly increased isokinetic knee extensor power (25\%), plantarflexor power (43\%), and fast gait velocity (5.9\%). Gait mechanics underlying the improved fast gait velocity included increases in hip angular impulse (29\%) and H1 work (37\%) and no changes in positive knee (K2) and A2 work. Detraining further improved fast gait velocity (4.7\%) with reductions in H1(-35\%), and increases in K2 (36\%) and A2 (7\%). Conclusion: Power training increased fast gait velocity in healthy old adults by increasing the reliance on hip muscle function and thus further strengthened the age-related distal-to-proximal shift in muscle function. (C) 2016 Elsevier B.V. All rights reserved.},
  language  = {en}
}
@misc{LacroixHortobagyiBeurskensetal.2017,
  author    = {Lacroix, Andre and Hortobagyi, Tibor and Beurskens, Rainer and Granacher, Urs},
  title     = {Effects of Supervised vs. Unsupervised Training Programs on Balance and Muscle Strength in Older Adults: A Systematic Review and Meta-Analysis},
  series = {Sports medicine},
  volume    = {47},
  journal   = {Sports medicine},
  publisher = {Springer},
  address   = {Northcote},
  issn      = {0112-1642},
  doi       = {10.1007/s40279-017-0747-6},
  pages     = {2341 -- 2361},
  year      = {2017},
  abstract  = {Objectives The objective of this systematic review and meta-analysis was to quantify the effectiveness of supervised vs. unsupervised balance and/or resistance training programs on measures of balance and muscle strength/ power in healthy older adults. In addition, the impact of supervision on training-induced adaptive processes was evaluated in the form of dose-response relationships by analyzing randomized controlled trials that compared supervised with unsupervised trials. Data Sources A computerized systematic literature search was performed in the electronic databases PubMed, Web of Science, and SportDiscus to detect articles examining the role of supervision in balance and/or resistance training in older adults. Study Eligibility Criteria The initially identified 6041 articles were systematically screened. Studies were included if they examined balance and/or resistance training in adults aged >= 65 years with no relevant diseases and registered at least one behavioral balance (e.g., time during single leg stance) and/or muscle strength/ power outcome (e.g., time for 5-Times-Chair-Rise-Test). Finally, 11 studies were eligible for inclusion in this meta-analysis. Study Appraisal Weighted mean standardized mean differences between subjects (SMDbs) of supervised vs. unsupervised balance/resistance training studies were calculated. The included studies were coded for the following variables: number of participants, sex, age, number and type of interventions, type of balance/strength tests, and change (\%) from pre- to post-intervention values. Additionally, we coded training according to the following modalities: period, frequency, volume, modalities of supervision (i.e., number of supervised/unsupervised sessions within the supervised or unsupervised training groups, respectively). Heterogeneity was computed using I 2 and chi(2) statistics. The methodological quality of the included studies was evaluated using the Physiotherapy Evidence Database scale. Results Our analyses revealed that in older adults, supervised balance/resistance training was superior compared with unsupervised balance/resistance training in improving measures of static steady-state balance (mean SMDbs = 0.28, p = 0.39), dynamic steady-state balance (mean SMDbs = 0.35, p = 0.02), proactive balance (mean SMDbs = 0.24, p = 0.05), balance test batteries (mean SMDbs = 0.53, p = 0.02), and measures of muscle strength/power (mean SMDbs = 0.51, p = 0.04). Regarding the examined dose-response relationships, our analyses showed that a number of 10-29 additional supervised sessions in the supervised training groups compared with the unsupervised training groups resulted in the largest effects for static steady-state balance (mean SMDbs = 0.35), dynamic steady-state balance (mean SMDbs = 0.37), and muscle strength/power (mean SMDbs = 1.12). Further, >= 30 additional supervised sessions in the supervised training groups were needed to produce the largest effects on proactive balance (mean SMDbs = 0.30) and balance test batteries (mean SMDbs = 0.77). Effects in favor of supervised programs were larger for studies that did not include any supervised sessions in their unsupervised programs (mean SMDbs: 0.28-1.24) compared with studies that implemented a few supervised sessions in their unsupervised programs (e.g., three supervised sessions throughout the entire intervention program; SMDbs: -0.06 to 0.41). Limitations The present findings have to be interpreted with caution because of the low number of eligible studies and the moderate methodological quality of the included studies, which is indicated by a median Physiotherapy Evidence Database scale score of 5. Furthermore, we indirectly compared dose-response relationships across studies and not from single controlled studies. Conclusions Our analyses suggest that supervised balance and/or resistance training improved measures of balance and muscle strength/power to a greater extent than unsupervised programs in older adults. Owing to the small number of available studies, we were unable to establish a clear dose-response relationship with regard to the impact of supervision. However, the positive effects of supervised training are particularly prominent when compared with completely unsupervised training programs. It is therefore recommended to include supervised sessions (i.e., two out of three sessions/week) in balance/resistance training programs to effectively improve balance and muscle strength/power in older adults.},
  language  = {en}
}
@article{BeijersbergenGranacherGaebleretal.2017,
  author    = {Beijersbergen, Chantal M. I. and Granacher, Urs and G{\"a}bler, Martijn and Devita, Paul and Hortobagyi, Tibor},
  title     = {Power Training-induced Increases in Muscle Activation during Gait in Old Adults},
  series = {Medicine and science in sports and exercise : official journal of the American College of Sports Medicine},
  volume    = {49},
  journal   = {Medicine and science in sports and exercise : official journal of the American College of Sports Medicine},
  publisher = {Lippincott Williams \& Wilkins},
  address   = {Philadelphia},
  issn      = {0195-9131},
  doi       = {10.1249/MSS.0000000000001345},
  pages     = {2198 -- 2205},
  year      = {2017},
  abstract  = {Introduction/Purpose: Aging modifies neuromuscular activation of agonist and antagonist muscles during walking. Power training can evoke adaptations in neuromuscular activation that underlie gains in muscle strength and power but it is unknown if these adaptations transfer to dynamic tasks such as walking. We examined the effects of lower-extremity power training on neuromuscular activation during level gait in old adults. Methods: Twelve community-dwelling old adults (age >= 65 yr) completed a 10-wk lower-extremity power training program and 13 old adults completed a 10-wk control period. Before and after the interventions, we measured maximal isometric muscle strength and electromyographic (EMG) activation of the right knee flexor, knee extensor, and plantarflexor muscles on a dynamometer and we measured EMG amplitudes, activation onsets and offsets, and activation duration of the knee flexors, knee extensors, and plantarflexors during gait at habitual, fast, and standardized (1.25 +/- 0.6 m.s(-1)) speeds. Results: Power training-induced increases in EMG amplitude (similar to 41\%; 0.47 <= d <= 1.47; P <= 0.05) explained 33\% (P = 0.049) of increases in isometric muscle strength (similar to 43\%; 0.34 <= d <= 0.80; P <= 0.05). Power training-induced gains in plantarflexor activation during push-off (+11\%; d = 0.38; P = 0.045) explained 57\% (P = 0.004) of the gains in fast gait velocity (+4\%; d = 0.31; P = 0.059). Furthermore, power training increased knee extensor activation (similar to 18\%; 0.26 <= d <= 0.29; P <= 0.05) and knee extensor coactivation during the main knee flexor burst (similar to 24\%, 0.26 <= d <= 0.44; P <= 0.05) at habitual and fast speed but these adaptations did not correlate with changes in gait velocity. Conclusions: Power training increased neuromuscular activation during isometric contractions and level gait in old adults. The power training-induced neuromuscular adaptations were associated with increases in isometric muscle strength and partly with increases in fast gait velocity.},
  language  = {en}
}