How to benefit from augmented feedback? The influence of motivational and informational content of augmented feedback and the influence of task complexity.

Augmented feedback (aF) positively influences motor performance by enhancing motivation and/or by providing information about task execution. It was speculated that aF-induced performance increments that rely on motivation should also occur when providing incorrect aF, while performance increments that rely on guidance towards "successful executions" (i.e. improved performances) should only occur when aF is correct. We further hypothesised that the informational content of aF is more important in more complex motor tasks. Thus, 32 participants received two forms of aF (correct, incorrect) during maximal voluntary contractions (MVC's; maximise force without time constraints; less complex) and maximal explosive contractions (MEC's; maximise force in the shortest possible way; more complex) of the knee extensors. Peak torque (MVC), peak rate of torque development (MEC) and EMG signals of rectus femoris (RF) and vastus lateralis were recorded. Correct and incorrect aF significantly enhanced MVC performance, indicating that performance improvements resulted mainly from the motivational property of aF. The observed trend towards increased RF muscle activity supports this conclusion. In contrast, while correct aF positively impacted MEC performance, incorrect aF had a negative influence. This indicates that the informational property of aF guided participants towards movement executions resulting in improved (correct aF) or decreased (incorrect aF) performances. The observed simultaneous decrease in muscle activity suggests that participants changed motor strategy, supporting the guiding role of aF. Our results demonstrate that the motivational aspect of aF dominates in maximal tasks with lower complexity (MVC), while the informational aspect is used during more complex maximal tasks (MEC).

Augmented feedback (aF) can influence performance by enhancing the motivation and/or by providing information about the execution of a task.Our results demonstrate that over the short-term, the motivational aspect of aF dominates in maximal tasks with lower complexity (maximal voluntary contractions). In contrast, the informational aspect will predominantly be used during more complex maximal tasks (maximal explosive contractions).This is the first study distinguishing between the motivational and informational aspects of aF during maximal motor tasks. Future research should focus on the long-term effects of these two separate aspects of aF.

Countermovement Jump Training Is More Effective Than Drop Jump Training in Enhancing Jump Height in Non-professional Female Volleyball Players.

The aim of the present study was to compare the effects of countermovement jump (CMJ) and drop jump (DJ) training on the volleyball-specific jumping ability of non-professional female volleyball players. For that purpose, 26 female volleyball players (15-32 years) were assigned to either a CMJ (20.4 ± 3.1 years, 171.0 ± 3.0 cm) or a DJ training group (22.0 ± 4.4 years, 168.2 ± 5.0 cm), which performed a six-week jump training (two sessions per week, 60 jumps per session). Each group performed 20% of the jumps in the jump type of the other group in order to minimize the influence of enhanced motor coordination on the differences between groups regarding the improvements of jump performance. Before and after the training, jump height was assessed in four jump types, including the trained and volleyball-specific jump types. Although both training forms substantially improved jump height, the CMJ training was significantly more effective in all jump types (17 vs. 7% on average; p < 0.001). This suggests that, at least for non-professional female volleyball players and a training duration of six weeks, training with a high percentage of CMJs is more effective than one with a high percentage of DJs. We hypothesize that this might be related to the slower stretch-shortening cycle during CMJs, which seems to be more specific for these players and tasks. These findings should support volleyball coaches in designing optimal jump trainings.

Age-dependent adaptations to anticipated and non-anticipated perturbations after balance training in children.

Postural control undergoes rapid changes during child development. However, the influence of balance training (BT) on the compensation of perturbations has not yet been investigated in children. For this purpose, young (6.7 ±â€¯0.6 years) and old children (12.0 ±â€¯0.4 years) were exposed to externally induced anticipated (direction known) and non-anticipated (direction unknown) perturbations on a free swinging platform before and after either child-oriented BT (INT; young: n = 12, old: n = 18) or regular physical education (CON; young: n = 9, old: n = 9). At baseline, old children exhibited less platform sway after perturbations than young children (p = .004; η2p = 0.17). However, no differences were found between anticipated and non-anticipated perturbations. After training, INT reduced the platform sway path while CON remained stable (-11.1% vs. +2.7%; p < .001; η2p = 0.26). Furthermore, the young INT group adapted statistically similarly in anticipated and non-anticipated situations (-7.9% vs. -12.6%; p = .556; r = 0.33), whereas the old INT group tended to improve more in anticipated perturbations (-15.1% vs. -8.2%; p = .052; r = 0.51). Thus, the maturity of the postural system seems to influence the extent of training adaptations in anticipated perturbations. Furthermore, this study provides evidence that BT can improve postural responses to external perturbations in children and may represent a useful intervention to prevent falls.

Is Young Age a Limiting Factor When Training Balance? Effects of Child-Oriented Balance Training in Children and Adolescents.

PURPOSE: Balance training (BT) studies in children reported conflicting results without evidence for improvements in children under the age of 8. The aim of this study therefore was to compare BT adaptations in children of different age groups to clarify whether young age prevents positive training outcomes. METHODS: The effects of 5 weeks of child-oriented BT were tested in 77 (38 girls and 39 boys) participants of different age groups (6-7 y, 11-12 y, and 14-15 y) and compared with age-matched controls. Static and dynamic postural control, explosive strength, and jump height were assessed. RESULTS: Across age groups, dynamic postural sway decreased (-18.7%; P = .012; [Formula: see text]) and explosive force increased (8.6%; P = .040; [Formula: see text]) in the intervention groups. Age-specific improvements were observed in dynamic postural sway, with greatest effects in the youngest group (-28.8%; P = .026; r = .61). CONCLUSION: In contrast to previous research using adult-oriented balance exercises, this study demonstrated for the first time that postural control can be trained from as early as the age of 6 years in children when using child-oriented BT. Therefore, the conception of the training seems to be essential in improving balance skills in young children.

Preparatory cortical and spinal settings to counteract anticipated and non-anticipated perturbations.

Little is known about how the central nervous system prepares postural responses differently in anticipated compared to non-anticipated perturbations. To investigate this, participants were exposed to translational and rotational perturbations presented in a blocked (anticipated) and a random (non-anticipated) design. The preparatory setting ('central set') was measured by H-reflexes, motor-evoked potentials (MEPs), and short-interval intracortical inhibition (SICI) shortly before perturbation onset in the soleus of 15 healthy adults. Additionally, the behavioral consequences of differential preparatory settings were analyzed by comparing the short- (SLR), medium- (MLR), and long-latency response (LLR) of the soleus after anticipated and non-anticipated rotations and translations. H-reflexes elicited before perturbation were different between conditions (p=0.023) with larger amplitudes in anticipated translations compared to anticipated rotations (37.0%; p=0.048). Reduced SICI was found in the three conditions containing perturbations compared to static standing (p<0.001). Muscular responses assessed after perturbations remained unchanged for the SLR and MLR, whereas the LLR was decreased in anticipated rotations (-36.2%; p=0.002) and increased in anticipated translations (16.7%; p=0.046) compared to the corresponding non-anticipated perturbation. As the SLR and MLR are organized at the spinal and the LLR at the cortical level, the preparatory setting seems to mainly influence cortically mediated postural responses. However, the modulation of the H-reflex before anticipated perturbations indicates that supraspinal centers adjusted Ia-afferent transmission for the soleus in a perturbation-specific manner. Intracortical inhibition was also modulated but differentiates to a lesser extent only between perturbation conditions and unperturbed stance.

Behavioral and neural adaptations in response to five weeks of balance training in older adults: a randomized controlled trial.

BACKGROUND: While the positive effect of balance training on age-related impairments in postural stability is well-documented, the neural correlates of such training adaptations in older adults remain poorly understood. This study therefore aimed to shed more light on neural adaptations in response to balance training in older adults. METHODS: Postural stability as well as spinal reflex and cortical excitability was measured in older adults (65-80 years) before and after 5 weeks of balance training (n = 15) or habitual activity (n = 13). Postural stability was assessed during one- and two-legged quiet standing on a force plate (static task) and a free-swinging platform (dynamic task). The total sway path was calculated for all tasks. Additionally, the number of errors was counted for the one-legged tasks. To investigate changes in spinal reflex excitability, the H-reflex was assessed in the soleus muscle during quiet upright stance. Cortical excitability was assessed during an antero-posterior perturbation by conditioning the H-reflex with single-pulse transcranial magnetic stimulation. RESULTS: A significant training effect in favor of the training group was found for the number of errors conducted during one-legged standing (p = .050 for the static and p = .042 for the dynamic task) but not for the sway parameters in any task. In contrast, no significant effect was found for cortical excitability (p = 0.703). For spinal excitability, an effect of session (p < .001) as well as an interaction of session and group (p = .009) was found; however, these effects were mainly due to a reduced excitability in the control group. CONCLUSIONS: In line with previous results, older adults' postural stability was improved after balance training. However, these improvements were not accompanied by significant neural adaptations. Since almost identical studies in young adults found significant behavioral and neural adaptations after four weeks of training, we assume that age has an influence on the time course of such adaptations to balance training and/or the ability to transfer them from a trained to an untrained task.

Maximizing Performance: Augmented Feedback, Focus of Attention, and/or Reward?

PURPOSE: Different approaches like providing augmented feedback (aF), applying an external focus of attention (EF), or rewarding participants with money (RE) have been shown to instantly enhance motor performance. So far, these approaches have been tested either in separate studies or directly against each other. However, there is no study that combined aF, EF, and/or RE to test whether this provokes additional benefits. The aim of the present study was therefore to identify the most powerful combination. METHODS: Eighteen participants performed maximal countermovement jumps in six different conditions: neutral (NE), aF, RE, aF + EF, aF + RE, and aF + EF + RE. RESULTS: Participants demonstrated the highest jump heights with aF + EF, followed by aF + EF + RE, aF + RE, aF, RE, and finally, NE. Activity of the M. rectus femoris differed significantly between conditions resulting in lower muscular activity in aF + EF and aF + EF + RE compared with NE. All other parameters, such as ground reaction forces and joint angles, were comparable across conditions. CONCLUSIONS: This is the first study showing superior performance when combining aF with EF. As reduced muscular activity was found only in conditions with EF, it is argued in line with the constrained action hypothesis that adopting an EF improves movement efficiency. In contrast, aF seems to rather enhance (intrinsic) motivation. However, monetary reward did not further amplify performance.