Discussion
BLIND
This is the first study that investigated whether a single-session VR-based balance training led to changes in weight-shifting behavior and brain activity in older adults. Older adults were able to improve their weight-shifting capacity after the session during ST and DT test-conditions, the latter reflecting that the gains were resistant to DT-interference. In addition, and as hypothesized, training effects were retained after 24 h and transferred to improved limits of stability outside the game-setting, though this transfer was only present in two directions and disappeared the next day. We also hypothesized that training-induced changes in HbOThe finding that EXP displayed better weight-shifting compared to CTR was not only confirmed by better game outcomes (increases in wasp-hits), but more importantly by a better control of the CoM (higher speed and accuracy). Learning led to larger effect sizes in EXP (speed: d ≥ 0.94) versus CTR (speed: d ≤ 0.09), which were retained over a 24 h-retention period. These findings are in line with a systematic review on balance training in older adultsNext, we could also demonstrate that weight-shift training effects were resilient to DT interference. Similar results were found in other studies investigating DT balance trainingImportantly, after mediolateral weight-shift training the EXP showed improvements of the stability limits in two directions. These fLOS gains could be considered as indications of near-transfer, referring to the greater likelihood to generalize learning outcomes when a high degree of similarity between the learned and the transfer task is apparentAs for neural activity, previous work demonstrated that changes in the brain are different for acquisition than retentionA similar pattern of results was found in the left SSC during DT-assessment, revealing an increase in HbOEven though we expected that early learning from pre- to post-training would require an increasing need for attentionEarlier work also showed that learning is often accompanied by a shift of activity to subcortical regionsThis study represented a randomized controlled trial, whereby the tester was not blind to group allocation and the contrast included a passive control group. However, outcomes were based on objective measures. Due to an error in the a-priori sample size calculation, this study was probably underpowered for some outcomes. However, effect sizes of the significant results were higher than the sensitivity power analysis-derived threshold. In addition, the modest reliability of repeated fNIRS measures in some regions hampered a strong interpretation of the results. To optimize the validity of the fNIRS data, we incorporated short-separation channels and accelerometers into the setup and analysis, filtering out movement artefacts and systemic noise as stipulated by recent guidelinesHowever, the fact that weight-shifting capacity in older adults was improved with a single session of training is promising and supports the incorporation of weight-shifting VR-games in fall-prevention programs. Another important finding for the clinical field was that the results were also present in conditions with cognitive distraction, implying robust learning results. Future research is needed to investigate whether enriched weight-shift training can induce sustained neural changes and lead to transfer effects to overall balance capacity in older adults.This study showed that a single training session improved mediolateral weight-shifting capacity in healthy older adults during both ST and DT assessments when compared to a control group without training. The gains were maintained after 24 h and showed short-term transfer to improvement of the limits of stability, although not in the mediolateral direction. The increased HbO