Preserving Agency During Electrical Muscle Stimulation Training Speeds up Reaction Time Directly After Removing EMS

Title of the Paper

Preserving Agency During Electrical Muscle Stimulation Training Speeds up Reaction Time Directly After Removing EMS

Paper Information

• Research Domain: Human-computer interaction and force feedback devices, particularly applications based on electrical stimulation technology
• Keywords: agency, electrical muscle stimulation (EMS), reaction time, force feedback devices, human-computer interaction, sensory feedback, neuroplasticity, motor adaptation, visual reaction, training effects

Research Background and Problem Statement

• Identified Problems or Challenges:

  • Force feedback devices (e.g., mechanical exoskeletons or EMS) can accelerate users' reaction times, but existing studies have only explored effects during device usage, leaving the sustained effects after device removal underexplored.
  • It remains unclear whether passive external acceleration can influence long-term human adaptability.

• Importance of the Problem:

  • Accelerating reaction times is crucial in many human-computer interaction scenarios, such as computer operations, sports, and emergency responses in hazardous environments (e.g., avoiding traffic accidents).
  • Investigating the long-term adaptability of reaction times can inspire the design of more efficient learning systems and expand human capabilities.

• Research Motivation and Related Work:

  • EMS devices can induce muscle movement through electrical stimulation, providing robust proprioceptive feedback that aids skill training, navigation, and reaction time acceleration.
  • Previous studies found that when EMS stimulation is triggered 40ms before the user's reaction time, it can simultaneously accelerate movements while preserving partial agency (i.e., "pre-volitional behavior").
  • However, these studies lack exploration of users' long-term adaptability and the transferability of training effects.

Proposed Solution

• Method or Solution:

  • The authors hypothesize that optimizing EMS training effects by preserving "agency"—allowing users to perceive movements as self-initiated rather than passively accelerated—can enhance training outcomes.
  • The experimental design includes three training conditions:
    1. Fast-EMS: Muscle movements are triggered synchronously with LED visual stimuli, achieving significant acceleration but without user agency.
    2. Agency-EMS: EMS stimulation is triggered 40ms earlier, aligning with the user's volitional reaction time and preserving partial agency.
    3. Late-EMS: EMS stimulation is triggered after the user completes the volitional movement, fully preserving agency but without acceleration effects.

• Innovative Contributions:

  • The study systematically investigates the sustained effects of EMS acceleration after device removal for the first time.
  • It proposes and experimentally validates the hypothesis that "agency" plays a critical role in reaction acceleration and adaptability.
  • The experiment simultaneously considers two relatively independent variables: agency and acceleration.

• Implementation Steps and Key Technologies:

  1. Measure participants' baseline visual reaction times (without EMS).
  2. Train participants under three conditions, using EMS devices to induce muscle movements.
  3. Test reaction times again after removing EMS devices, comparing pre- and post-training results.
  4. Experimental hardware includes customized touch sensors, LED visual stimuli, and EMS devices with a precision of approximately 1ms.

Research Findings

• Specific Results:

  • Only under the "Agency-EMS" training condition did participants exhibit significantly shortened reaction times after device removal, with an average acceleration of 8ms and up to 20ms for some participants.
  • The other two training conditions (Fast-EMS and Late-EMS) did not significantly improve reaction times after device removal.

• Advantages Compared to Existing Solutions:

  • Provides validation of long-term effects on users, extending beyond real-time effects during device usage.
  • Focuses on "agency," advancing the design of autonomous experiences in human-computer interaction.

• Experimental and Evaluation Results:

  • Statistical significance analyses (e.g., one-way repeated measures ANOVA) confirmed the reaction time acceleration effect under the "Agency-EMS" condition.
  • Subjective interviews revealed that participants had more positive emotional experiences, higher task focus, and a greater sense of control under the "Agency-EMS" condition.

• Limitations and Future Directions:

  • The study is limited to EMS devices and does not validate similar effects for other force feedback devices (e.g., mechanical exoskeletons).
  • The training period was relatively short, leaving the consolidation effects of longer-term and repeated training unexplored.
  • Future research could investigate the role of EMS in complex decision-making tasks and its potential applications in diverse scenarios (e.g., professional sports and video games).