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Locomotor stability is challenged by internal perturbations, e.g., motor noise, and
external perturbations, e.g., changes in surface compliance. One means to compensate
for such perturbations is to employ motor synergies, defined here as co-variation among
a set of elements that acts to stabilize, or provide similar trial-to-trial (or step-to-step)...
Similar publications
In the context of legged robotics, many criteria based on the control of the Center of Mass (CoM) have been developed to ensure stable and safe robot locomotion. Defining a whole-body framework with the control of the CoM requires a planning strategy, often based on a specific type of gait and reliable state-estimation. In a whole-body control appr...
Citations
... While this study focused on an immediate increase in motor flexibility, further investigation into retention and transfer effects is necessary. Some previous studies have shown the retention and transfer effects on learning motor flexibility in the reaching task [39,47], a force-production task [38,48], a two-finger force-exertion task [40,49], upright balance [50] and gait [51]. For example, Eckardt and Rosenblatt (2019) investigated whether resistance training in unstable environments could promote motor flexibility during walking [51]. ...
... Some previous studies have shown the retention and transfer effects on learning motor flexibility in the reaching task [39,47], a force-production task [38,48], a two-finger force-exertion task [40,49], upright balance [50] and gait [51]. For example, Eckardt and Rosenblatt (2019) investigated whether resistance training in unstable environments could promote motor flexibility during walking [51]. Older participants were randomly assigned to one of three training groups: stable whole-limb machine-based training, unstable freeweight training, and stable machine-based adductor/ abductor training. ...
... Older participants were randomly assigned to one of three training groups: stable whole-limb machine-based training, unstable freeweight training, and stable machine-based adductor/ abductor training. After the training of each group, motor flexibility during gait was improved in the unstable freeweight training group [51]. Yang et al. 2007 reported that the retention and transfer effects on motor flexibility in reaching movement were found in younger participants [39]. ...
Background
An age-related decline in motor flexibility, which is the ability to synergistically control the degrees of freedom of the body to ensure stable performance of a task, is a factor that contributes to falls. We investigated whether providing environmental constraints to increase the movement repertoire (i.e., the motor solution that works to achieve one’s goal), in combination with aiming at precise control of the performance, would be effective for improving motor flexibility, and whether the effect on the leading limb would extend to the trailing limb.
Methods
Fifteen older adults (75.1 ± 6.2 years and 14 younger adults (34.6 ± 5.0 years) performed under three walking conditions: walking normally and crossing the obstacle (normal), walking and crossing the obstacle with constraints of foot placement after stepping over it (constrained), and walking and crossing the obstacle with constraints as in the constrained condition, in addition to aiming for maintaining a constant clearance height at the moment of obstacle crossing (precision). An uncontrolled manifold analysis was used to quantify motor flexibility as the synergy index. The foot height at the moment of obstacle crossing was used as the performance variable and seven segmental angles were used as the elemental variables. A higher synergy index indicates greater motor flexibility.
Results
For the leading limb, the synergy index was significantly higher under the precision condition than those under the other conditions. This suggests that not only providing environmental constraints but also keeping constant the performance variable is critical to improving motor flexibility. Moreover, the effects of an increase in the synergy index in the leading limb extended to the trailing limb.
Conclusions
Providing environmental constraints to increase the movement repertoire while also aiming for precision in the performance variable was an effective method of improving motor flexibility during obstacle crossing for older adults.
... (22) In another research on dual task training that was a randomised control trial where the individuals were divided in three different groups, two groups had a mean age of 69.5 and 69.9 years respectively. (23) These mentioned research findings match the mean age of this research study, however, in one research assessing the elderly in an individual adjusted progressive group training program for older adults where the participants were divided in two different groups, the mean ages were 76 years and 78 years respectively this change is likely because the maximum age group individual in that study was 93 years unlike in the current research study where the maximum age was 80 years. (15) The mean timed up and go test before the application of exercises was 16.98 seconds and after exercise application was 15.77 seconds showing an improvement in the time taken to cover a distance of 3 meters. ...
... where N is the number of subjects. The synergy index ΔV is used to quantify the strength of the covariation in the synergies to stabilise the θ shoulder , and the Fisher z-transform is used to correct ΔV for a normal distribution [23]: ...
The jump smash is the most aggressive manoeuvre in badminton. Racket parameters may be the key factor affecting the performance of jump smash. Previous studies have focused only on the biomechanical characteristics of athletes or on racket parameters in isolation, with less observation of the overall performance of the human-racket system. This study aims to explore the effects of different racket weights on neuromuscular control strategies in advanced and beginner players. Nonnegative matrix factorisation (NMF) was used to extract the muscle synergies of players when jumping smash using different rackets (3U, 5U), and K-means clustering was used to obtain the fundamental synergies. Uncontrolled manifold (UCM) analyses were used to establish links between synergy and motor performance, and surface electromyography (sEMG) was mapped to each spinal cord segment. The study found significant differences ( P < 0.05 ) in the postural muscles of skilled players and significant differences ( P < 0.001 ) in the upper-limb muscles of beginners when the racket weight was increased. Advanced players adapt to the increase in racket weight primarily by adjusting the timing of the activation of the third synergy. Combined synergy in advanced players is mainly focused on the backswing, while that in beginners is mainly focused on the frontswing. This suggests that advanced players may be more adept at utilising the postural muscles and their coordination with the upper-limb muscles to adapt to different rackets. In addition, the motor experience can help athletes adapt more quickly to heavier rackets, and this adaptation occurs primarily by adjusting the temporal phase and covariation characteristics of the synergies rather than by increasing the number of synergies.
... In addition, such simple and uncomplicated devices would make it possible to perform the desired intensity and volume of strength training simultaneously with video game based cognitive tasks (Angevaren et al., 2007;Stanmore et al., 2017;Netz, 2019;Stojan and Voelcker-Rehage, 2019), without allowing the cognitive component to interfere with strength training which is a confounding factor in the literature (Fiatarone Singh et al., 2014;Stanmore et al., 2017;Joubert and Chainay, 2018;Rezola-Pardo et al., 2019;Stojan and Voelcker-Rehage, 2019). Furthermore, strength training alone has not been effective in influencing working memory (Landrigan et al., 2020), but combining it with simultaneous cognitive tasks (Eckardt and Rosenblatt, 2019) and memory tasks (Norouzi et al., 2019) can impact positively working memory. Therefore, also the specificity of the cognitive component should be considered along with the type of strength exposure, lack of interference, and other key factors maximizing the effectiveness of strength exergaming (Figure 2). ...
Background
Despite functional and cognitive benefits, few adults and older adults do strength training twice per week with sufficient intensity. Exercise-based active video games (exergaming) may amplify the cognitive benefits of exercise and increase adherence and motivation toward training. However, the benefits of a well-defined and monitored dose of strength training, executed simultaneously or sequentially with a cognitive element, has received little attention. In this study we have two aims: First, to systematically gather the available evidence; second, to suggest possible ways to promote strength exergaming innovations.
Methods
We systematically reviewed randomized controlled trials using simultaneous or sequent combined strength and cognitive training or strength exergaming to improve cognitive or functional outcomes in adults and older adults.
Results
After screening 1,785 studies (Google Scholar, ACM Digital Library, IEEE Xplore Library, PsycARTICLES, Scopus, Cochrane Library and PubMed) we found three eligible studies. Of the two studies using sequent strength and cognitive training, one showed improved functionality, but the other showed negative effects on cognition. The third study using simultaneous intervention, reported a positive influence on both cognition and function, when compared with either strength training alone or a control group. Moderate level of evidence was showed on GRADE analysis.
Conclusion
The existing little evidence suggests that strength and cognitive training improves cognition and function in adults and older adults. The following suggestions may help to promote further innovation: (1) ensure minimal dosage of strength training (30–60 min, 2 × /week), (2) use machine-based strength training devices to control volume and intensity (to prevent cognitive components from interfering with strength training), (3) include power training by using cognitive tasks requiring rapid reactions, and (4) add cognitive memory tasks (to extend the cognitive benefits of strength training per se), and (5) include motivational exergame elements to increase adherence.
... Krafttraining in metastabilen Gleichgewichtslagen für ältere Menschen stabilizer muscles) with a special focus on multijoint coordination during gait (13) and executive functions (14). All groups showed overall similar improvements in strength, balance, and the risk of falls measures. ...
... Second, when compared to traditional RT on stable supports, measures of muscle strength appeared to improve similarly or even larger (11). However, training loads were significantly smaller in MRT than in stable RT (12,13,35). As an important consequence, MRT may stress the joints to a smaller degree than traditional RT and its larger loads while producing similar effects. ...
... In contrast, Pirauá et al. (35) found improvements in balance performance based on the Berg Balance Scale across both MRT and RT groups with slightly better results for their MRT. Fourth, study results comparing locomotor and stabilizer RT on stable supports with MRT suggest that MRT could be beneficial for the strengthening of stabilizer muscles (13). Assuming that older adults are less exposed to daily activities stressing their leg stabilizer muscles a more pronounced strength decline as compared to locomotor muscles would be expected than in younger adults. ...
›Using resistance training on unstable supports or with instability devices athletes aim to prepare their neuromuscular system for sudden and unforeseen impairments in equilibrium impeded by the environment or through sports partners. In contrast to athletes, older adults aim to avoid such situations impeded by instability to reduce a possible risk of falling. The goal of this review is to outline the specific benefits of
resistance training on unstable supports or with instability devices, denote as metastability resistance training (MRT), in older adults while extending knowledge of past reviews in this field. Existing studies comparing MRT to traditional resistance training (RT) on stable surfaces are reviewed and summarized. Our review shows that MRT: a) is safe for the older adult when properly introduced and supervised; b) requires smaller training
loads and stresses larger articular areas while providing similar or larger gains in strength as traditional RT on stable surfaces; c) provides extended gains in functional mobility, balance, and power; d) offers a strengthening of stabilizer muscles whose strength loss is assumed to facilitate falls; e) stabilizes gait performance and, thus, reduces the risk of falls; f) improves cognitive performance reducing reductions the fear of falling and improves executive functions. Moreover, MRT was found to be particularly beneficial for Parkinson’s disease patients. Hence, MRT could be a very useful tool to complement the physical conditioning of older adults.
... If greater motor flexibility enables functional mobility then training paradigms that manipulate stability to facilitate exploration of motor solution and promote large amounts of good variance may be beneficial for increasing function and possibly preventing falls. Indeed, resistance training on unstable surfaces has been shown to promote motor flexibility (increase ΔV z and V UCM related to the same synergies considered in the current study) and to improve functional measures related to proactive balance in healthy OA (Eckardt and Rosenblatt 2019). ...
Motor flexibility, the ability to employ multiple motor strategies to meet task demands, may facilitate ambulation in complex environments that constrain movements; loss of motor flexibility may impair mobility. The purpose of this study was to determine the effects of obesity (a specific model of mobility impairment) and advanced age on motor flexibility during a task that constrained foot placement while walking. Twenty-one community-dwelling obese (OB) and 25 normal weight (NW) older adults (46 total older adults—OA) and 10 younger adults (YA) walked normally on a treadmill (baseline) then walked while stepping on lighted cues projected onto the treadmill at locations corresponding to average foot placement during normal walking (cued). The uncontrolled manifold (UCM) analysis was used to partition total variance in a set of seven lower-limb segment angles into components that did (“bad” variance) and did not (“good” variance) affect step-to-step variance in the trajectory of the swing foot. Motor flexibility was operationalized as an increase (baseline to cued) in total variance with an increase in good variance that exceeded the change in bad variance. There was no significant group × walking task interaction for total and good variance for OB vs NW, but there was a strong and significant interaction effect for OA vs YA (p < 0.01; Cohen’s d > 1.0). Whereas YA reduced both good and bad variance, OA increased good variance beyond the change in bad variance. In OA, these changes were associated with several functional measures of mobility. Cued walking may place greater demands on OA requiring greater reliance on motor flexibility, although otherwise healthy older obese adults may be able to compensate for functional and cognitive declines associated with obesity by increasing motor flexibility under such tasks. The extent to which motor flexibility is employed during novel or constrained tasks may be a biomarker of healthy aging and a target for (re)habilitation.
... Although, we can find conflicting results on muscle activation, the majority of studies found increased limb and trunk muscle activity during RT performed within unstable conditions (Behm & Colado, 2012). Related research on the effect of RT performed within unstable conditions found enhanced ability to control counter-rotation mechanisms for postural control (Silva, Mrachacz-Kersting, Oliveira, & Kersting, 2018) and lower extremity covariation to stabilise postural control, particular in more challenging walking conditions (Eckardt & Rosenblatt, 2019). The last study in particular demonstrates, that effects of RT performed on unstable surfaces may not be detected by traditional measures like vertical GRF or peak rate of force development, but non-specific measures focusing on covariation rather than maximal force / strength. ...
Instability resistance training (RT) or exercising within an unstable environment is a popular training modality and frequently used in training, rehabilitation and prevention settings. Yet, due to the reported reduced force output during exercising within unstable condition, instability RT is said to lack the necessary overload to induce meaningful effects. However, empirical evidence of interventions suggests otherwise. The aim of this study was to systematically analyse instability RT vs. stable RT and discuss potential mechanisms. Therefore, we analysed squats within more unstable and more stable environments and calculated transversal and vertical forces. Greater transversal plane ground reaction forces were observed while performing squats on the more unstable surface (p ≤ .001; d = 3.70, BF10 = 53213.49). In contrast, vertical force output remained similar for both conditions (p = .058; d = 1.14, BF10 = 1.36).
... Investigators used a combination of seated machines (leg press), squats, and walking with dumbbells over stable and unstable surfaces. 25 Our data show that ECCRT of CNCRT did not differentially change temporal spatial parameters of gait and gait variability. Machine-based resistance training, irrespective of muscle action type, may not facilitate improvements in motor exploration and reduction in variance during walking. ...
... Recent evidence suggests that inclusion of resistance exercise performed on a unstable surface (performed on foam pads and BoSUballs) may increase motor adaptability, motor output, and better responses to environmental conditions during walking. 25 Our seated machine intervention was more similarly aligned with the pneumatic machines used by Foroughi et al. 24 This investigation did not detect group by time interactions for pain or functional scores despite leg muscle strength gains. Potentially, higher speeds of more functional resistive movement at lower percentage of 1RM may be more functionally useful for the knee OA population. ...
Objective:
To compare the effectiveness of concentrically-focused resistance training (CNCRT) to eccentrically-focused resistance training (ECCRT) on physical function and functional pain in knee osteoarthritis (OA).
Design:
Randomized, single-blinded controlled four-month trial. Older adults with knee OA (N=88; 68.3±6.4 yr, 30.4±6.9 kg/m and 67.4% women) were randomized to ECCRT, CNCRT or no-exercise control (CON). Main outcomes included chair rise time, stair climb time, six-minute walk test distance, temporalspatial parameters of gait, community ambulation and functional pain.
Results:
Leg muscle strength improved in both training groups compared to CON. There were no significant group x time interactions for any functional performance score (chair rise time, stair climb time, six-minute walk test distance, gait parameters, community ambulation). Compared to CON, functional pain scores were reduced for chair rise (-38.6% CNCRT, -50.3% ECCRT vs +10.0%) and stair climb (-51.6% CNCRT, -41.3% ECCRT vs +80.7%; all p<0.05). Pain scores were reduced during the six-minute walk and in early recovery with CNCRT compared to the remaining two groups (p<0.05).
Conclusion:
Either resistance exercise type improves activity-related knee OA pain, but CNCRT more effectively reduced severity of ambulatory pain and pain upon walking cessation.
... Thus, balance appears to trigger neuroplasticity on multiple levels, structurally by increasing grey and white matter and by optimising signal processing and freeing cognitive resources. Interestingly, we found that instability resistance training affected motor signal processing by reducing motor noise during challenging locomotion 35 . The uncontrolled manifold control analysis (UCM) was used to calculate multijoint-covariation related to the stabilization of a particular performance variable. ...
... A recent consensus paper pointed out the cerebellum's role in movement and cognition, particularly the interaction of prefrontal structures and the function of the cerebellum in movement automatization, as well as mediating executive functions 36 . Given the effect of instability resistance training as a tool to reduce the motor noise through a better state estimation within the anticipatory control-loop 35 , the here reported improvements in executive functions, and the possible structural and functional connections, it appears obvious that instability resistance training benefits cognitive processes which in turn may positively affect motor control. ...
... Due to the relevance of cognition in fall prevention research and the distinctive nature of the field of research, we decided to publish and discuss the results for the cognitive tasks separately. The effects on locomotor control and proxies of strength and balance are published and discussed elsewhere 35 ...
Aging is associated with declines in physical and cognitive performance. While there is no doubt about beneficial effects of physical exercise on proxies of strength and balance, the overall evidence for positive effects of resistance and balance training on executive functions is rather inconsistent. Whether the simultaneous exercising of strength and balance, i.e., instability resistance training, promotes executive functions in older adults is unknown. In the present trial, we tested the effects of unstable vs. stable resistance training on executive functions. Sixty-eight healthy older adults aged 65–79 years were randomly assigned to either an instability free-weight resistance training or one of two stable machine-based resistance training programs. Each group exercised twice a week on non-consecutive days for 10 weeks. Four tests to evaluate specific domains of executive functions were administered prior and following training: working memory, processing speed, response inhibition and set-shifting. The instability resistance training group improved working memory, processing speed and response inhibition from pre to post-test. In contrast, we found no improvements in executive functions for both stable resistance training groups. Our results demonstrate that 10 weeks of instability resistance training suffice to improve executive functions in older adults.
