Rainer Beurskens

Neural Correlates of Dual-Task Walking: Effects of Cognitive versus Motor Interference in Young Adults

Walking while concurrently performing cognitive and/or motor interference tasks is the norm rather than the exception during everyday life and there is evidence from behavioral studies that it negatively affects human locomotion. However, there is hardly any information available regarding the underlying neural correlates of single- and dual-task walking. We had 12 young adults (23.8 ± 2.8 years) walk while concurrently performing a cognitive interference (CI) or a motor interference (MI) task. Simultaneously, neural activation in frontal, central, and parietal brain areas was registered using a mobile EEG system. Results showed that the MI task but not the CI task affected walking performance in terms of significantly decreased gait velocity and stride length and significantly increased stride time and tempo-spatial variability. Average activity in alpha and beta frequencies was significantly modulated during both CI and MI walking conditions in frontal and central brain regions, indicating an increased cognitive load during dual-task walking. Our results suggest that impaired motor performance during dual-task walking is mirrored in neural activation patterns of the brain. This finding is in line with established cognitive theories arguing that dual-task situations overstrain cognitive capabilities resulting in motor performance decrements.

Effects of Heavy-Resistance Strength and Balance Training on Unilateral and Bilateral Leg Strength Performance in Old Adults

The term “bilateral deficit” (BLD) has been used to describe a reduction in performance during bilateral contractions when compared to the sum of identical unilateral contractions. In old age, maximal isometric force production (MIF) decreases and BLD increases indicating the need for training interventions to mitigate this impact in seniors. In a cross-sectional approach, we examined age-related differences in MIF and BLD in young (age: 20–30 years) and old adults (age: >65 years). In addition, a randomized-controlled trial was conducted to investigate training-specific effects of resistance vs. balance training on MIF and BLD of the leg extensors in old adults. Subjects were randomly assigned to resistance training (n = 19), balance training (n = 14), or a control group (n = 20). Bilateral heavy-resistance training for the lower extremities was performed for 13 weeks (3 × / week) at 80% of the one repetition maximum. Balance training was conducted using predominately unilateral exercises on wobble boards, soft mats, and uneven surfaces for the same duration. Pre- and post-tests included uni- and bilateral measurements of maximal isometric leg extension force. At baseline, young subjects outperformed older adults in uni- and bilateral MIF (all p < .001; d = 2.61–3.37) and in measures of BLD (p < .001; d = 2.04). We also found significant increases in uni- and bilateral MIF after resistance training (all p < .001, d = 1.8-5.7) and balance training (all p < .05, d = 1.3-3.2). In addition, BLD decreased following resistance (p < .001, d = 3.4) and balance training (p < .001, d = 2.6). It can be concluded that both training regimens resulted in increased MIF and decreased BLD of the leg extensors (HRT-group more than BAL-group), almost reaching the levels of young adults.

Effects of Power Training on Mobility and Gait Biomechanics in Old Adults with Moderate Mobility Disability: Protocol and Design of the Potsdam Gait Study (POGS)

Background: Walking speed decreases in old age. Even though old adults regularly participate in exercise interventions, we do not know how the intervention-induced changes in physical abilities produce faster walking. The Potsdam Gait Study (POGS) will examine the effects of 10 weeks of power training and detraining on leg muscle power and, for the first time, on complete gait biomechanics, including joint kinematics, kinetics, and muscle activation in old adults with moderate mobility disability. Methods/Design: POGS is a randomized controlled trial with two arms, each crossed over, without blinding. Arm 1 starts with a 10-week control period to assess the reliability of the tests and is then crossed over to complete 25-30 training sessions over 10 weeks. Arm 2 completes 25-30 exercise sessions over 10 weeks, followed by a 10-week follow-up (detraining) period. The exercise program is designed to improve lower extremity muscle power. Main outcome measures are: muscle power, gait speed, and gait biomechanics measured at baseline and after 10 weeks of training and 10 weeks of detraining. Discussion: It is expected that power training will increase leg muscle power measured by the weight lifted and by dynamometry, and these increased abilities become expressed in joint powers measured during gait. Such favorably modified powers will underlie the increase in step length, leading ultimately to a faster walking speed. POGS will increase our basic understanding of the biomechanical mechanisms of how power training improves gait speed in old adults with moderate levels of mobility disabilities.

Postural Control in Dual-Task Situations: Does Whole-Body Fatigue Matter?

Postural control is important to cope with demands of everyday life. It has been shown that both attentional demand (i.e., cognitive processing) and fatigue affect postural control in young adults. However, their combined effect is still unresolved. Therefore, we investigated the effects of fatigue on single- (ST) and dual-task (DT) postural control. Twenty young subjects (age: 23.7 ± 2.7) performed an all-out incremental treadmill protocol. After each completed stage, one-legged-stance performance on a force platform under ST (i.e., one-legged-stance only) and DT conditions (i.e., one-legged-stance while subtracting serial 3s) was registered. On a second test day, subjects conducted the same balance tasks for the control condition (i.e., non-fatigued). Results showed that heart rate, lactate, and ventilation increased following fatigue (all p < 0.001; d = 4.2–21). Postural sway and sway velocity increased during DT compared to ST (all p < 0.001; d = 1.9–2.0) and fatigued compared to non-fatigued condition (all p < 0.001; d = 3.3–4.2). In addition, postural control deteriorated with each completed stage during the treadmill protocol (all p < 0.01; d = 1.9–3.3). The addition of an attention-demanding interference task did not further impede one-legged-stance performance. Although both additional attentional demand and physical fatigue affected postural control in healthy young adults, there was no evidence for an overadditive effect (i.e., fatigue-related performance decrements in postural control were similar under ST and DT conditions). Thus, attentional resources were sufficient to cope with the DT situations in the fatigue condition of this experiment.

Effects of Backpack Carriage on Dual-Task Performance in Children During Standing and Walking

ABSTRACT Primary school children perform parts of their everyday activities while carrying school supplies and being involved in attention-demanding situations. Twenty-eight children (8–10 years old) performed a 1-legged stance and a 10 m walking test under single- and dual-task situations in unloaded (i.e., no backpack) and loaded conditions (i.e., backpack with 20% of body mass). Results showed that load carriage did not significantly influence childrens standing and walking performance (all p > .05), while divided attention affected all proxies of walking (all p < .001). Last, no significant load by attention interactions was detected. The single application of attentional but not load demand negatively affects childrens walking performance. A combined application of both did not further deteriorate their gait behavior.

Effects of drop height and surface instability on neuromuscular activation during drop jumps

The purpose of this study was to examine whether drop height‐induced changes in leg muscle activity during drop jumps (DJ) are additionally modulated by surface condition. Twenty‐four healthy participants (23.7 ± 1.8 years) performed DJs on a force plate on stable, unstable, and highly unstable surfaces using different drop heights (i.e., 20 cm, 40 cm, 60 cm). Electromyographic (EMG) activity of soleus (SOL), gastrocnemius (GM), tibialis anterior (TA) muscles and coactivation of TA/SOL and TA/GM were analyzed for time intervals 100 ms prior to ground contact (preactivation) and 30–60 ms after ground contact [short latency response (SLR)]. Increasing drop heights resulted in progressively increased SOL and GM activity during preactivation and SLR (P < 0.01; 1.01 ≤ d ≤ 5.34) while TA/SOL coactivation decreased (P < 0.05; 0.51 ≤ d ≤ 3.01). Increasing surface instability produced decreased activities during preactivation (GM) and SLR (GM, SOL) (P < 0.05; 1.36 ≤ d ≤ 4.30). Coactivation increased during SLR (P < 0.05; 1.50 ≤ d ≤ 2.58). A significant drop height × surface interaction was observed for SOL during SLR. Lower SOL activity was found on unstable compared to stable surfaces for drop heights ≥40 cm (P < 0.05; 1.25 ≤ d ≤ 2.12). Findings revealed that instability‐related changes in activity of selected leg muscles are minimally affected by drop height.

Effects of Standardized Home Training in Patients with Cognitive Impairment following Geriatric Rehabilitation: A Randomized Controlled Pilot Study

Background: Post-ward geriatric rehabilitation programs have hardly been developed and validated, which leaves a substantial gap in rehabilitative care in older adults and hinders full exploitation of maintained, but often unrecognized rehabilitation potentials. Geriatric rehabilitation patients with cognitive impairment represent a highly vulnerable population which is often affected by a lack of an ongoing support at the intersection between ward-based and post-ward rehabilitation. Objective: To determine the effect of a standardized home-based training program in geriatric patients with cognitive impairment following ward-based rehabilitation. Methods: A randomized controlled, single-blinded intervention trial (RCT) with wait list control design was used. Geriatric patients (n = 34; age: 81.9 ± 5.7 years) with cognitive impairment (MMSE: 18.8 ± 4.7), identified by predefined in- and exclusion criteria, were consecutively recruited from a geriatric rehab ward. Patients in the intervention group (IG, n = 17) performed a 6-week strength and functional home training. The control group (CG, n = 17) started an identical training 6 weeks later with an initial usual care period during the intervention for the IG. Functional performance (Short Physical Performance Battery; SPPB), clinically relevant functional deficits (Performance Oriented Assessment; POMA), and physical activity (Assessment of Physical Activity For Older Persons questionnaire; APAFOP) represented primary outcome measurements complemented by additional secondary outcome parameters. Results: The IG significantly increased functional performances in SPPB (total score: p = 0.012; chair rise: p = 0.007, balance: p = 0.066), reduced gait and balance deficits in POMA (total score: p = 0.006; balance: p = 0.034; gait: p = 0.019), and increased physical activity (APAFOP; p = 0.05) compared to the CG. Effect sizes showed medium to large effects for significant parameters (eta2 = 0.14-0.45). Training benefits and adherence were more pronounced following the immediate onset of post-ward training compared to a delayed start (eta2 = 0.06-0.23). Conclusion: Results of this pilot study show that a feasible and easy to handle, home-based rehabilitation program increased functional performance and physical activity in a vulnerable, multimorbid patient group with cognitive impairment, in particular when the post-ward training onset was not postponed.

Contents Vol. 62, 2016

Clinical Section D. Aarsland, Stockholm J. Attems, Newcastle upon Tyne M. Burtscher, Innsbruck G. Del Giudice, Siena V.C. Emery, Guildford J.D. Erusalimsky, Cardiff L. Fontana, St. Louis, Mo. J.J. Goronzy, Stanford, Calif. U. Granacher, Potsdam K. Hauer, Heidelberg F. Kronenberg, Innsbruck T.F. Lue, San Francisco, Calif. A.B. Maier, Parkville, Vic. J. Olshansky, Chicago, Ill. A. Stuck, Bern T.M. Stulnig, Vienna J. Tao, Guangzhou D.C. Willcox, Ginowan D. Ziegler, Düsseldorf