Matlab_Codes_for_Processing/calculateMVC.m

function [mvc, mvc_group_num] = calculateMVC(subject_data, emg_device_number, emg_fs, task_name_list, mvc_trial_target_mvc_emg_list)
% calculateMVC calculates the maximum voluntary contraction (MVC) values
% from EMG signals collected during multiple tasks and trials.
%
% INPUTS:
%   subject_data                 : Processed EMG data for a single subject
%   emg_device_number            : Number of EMG sensors used
%   emg_fs                       : Sampling frequency of EMG signals (Hz)
%   task_name_list               : List of tasks performed in the experiment
%   mvc_trial_target_mvc_emg_list: Mapping of MVC trials to target EMG channels
%
% OUTPUTS:
%   mvc            : Calculated MVC values for each task and muscle
%   mvc_group_num  : Number indicating MVC groups based on task or trial
%
% Author: Junyo Boo (2025)
% Data DOI: https://doi.org/10.6084/m9.figshare.27677016
%
% The following script is provided under the Creative Commons Attribution 4.0
% International License (CC-BY 4.0).
%
% You are free to share and adapt this material for any purpose, even commercially,
% provided you give appropriate credit, provide a link to the license, and indicate
% if changes were made. The full license text can be found at:
%
% https://creativecommons.org/licenses/by/4.0/
%
%---------------------------------------------------------------------------------------


    task_number = length(task_name_list);
    mvc_measurement = [];
    for task_idx = 1:task_number
        task_name = task_name_list(task_idx);

        mvc_emg_env_data = subject_data.(task_name).MVC_envs;
        mvc_number = numel(fieldnames(mvc_emg_env_data));
        temp_task_mvc = zeros(1,emg_device_number);
        for mvc_idx = 1:mvc_number
            mvc_trial_name = sprintf("Trial%02d",mvc_idx);
            target_mvc_emg_data = table2array(mvc_emg_env_data.(mvc_trial_name)(:,mvc_trial_target_mvc_emg_list{mvc_idx}));
            temp_trial_target_mvc = get_mvc(target_mvc_emg_data, emg_fs, 1);
            temp_task_mvc(mvc_trial_target_mvc_emg_list{mvc_idx}) = max(temp_task_mvc(mvc_trial_target_mvc_emg_list{mvc_idx}), temp_trial_target_mvc);
        end
        mvc_measurement = cat(1, mvc_measurement, temp_task_mvc);
    end
    [~, ~, group_index] = unique(mvc_measurement, 'rows');
    mvc_group_num = max(group_index);
    mvc = zeros(task_number, emg_device_number);
    mvc_cell = cell(1,mvc_group_num);
    mvc_max = zeros(mvc_group_num, emg_device_number);

    for task_idx = 1:task_number
        task_name = task_name_list(task_idx);
        mvc_task_tot = [];
        mvc_emg_env_data = subject_data.(task_name).MVC_envs;
        mvc_number = numel(fieldnames(mvc_emg_env_data));
        temp_task_mvc = zeros(1,emg_device_number);
        for mvc_idx = 1:mvc_number
            mvc_trial_name = sprintf("Trial%02d",mvc_idx);
            target_mvc_emg_data = table2array(mvc_emg_env_data.(mvc_trial_name)(:,mvc_trial_target_mvc_emg_list{mvc_idx}));
            temp_trial_target_mvc = calculate_mvc(target_mvc_emg_data, emg_fs, 1);
            temp_task_mvc(mvc_trial_target_mvc_emg_list{mvc_idx}) = max(temp_task_mvc(mvc_trial_target_mvc_emg_list{mvc_idx}), temp_trial_target_mvc);
        end
        mvc_task_tot = cat(1, mvc_task_tot, temp_task_mvc);

        for trial_idx = subject_data.(task_name).AvailableTrialIdx
            trial_name = sprintf("Trial%02d",trial_idx);
            nSteps = subject_data.(task_name).(trial_name).nSteps;
            for step_idx = 1:nSteps
                step_name = sprintf("Step%02d", step_idx);
                temp_trial_mvc_emg_data = subject_data.(task_name).(trial_name).(step_name).EMGs_env;
                target_mvc_emg_data = table2array(temp_trial_mvc_emg_data);
                temp_trial_target_mvc = calculate_mvc(target_mvc_emg_data, emg_fs, 1);
            end
            mvc_task_tot = cat(1, mvc_task_tot, temp_trial_target_mvc);
        end
        mvc_cell{group_index(task_idx)} = cat(1, mvc_cell{group_index(task_idx)}, mvc_task_tot);
    end

    for mvc_group_idx=1:mvc_group_num
        mvc_max(mvc_group_idx,:) = max(mvc_cell{mvc_group_idx});
    end

    for task_idx = 1:task_number
        mvc(task_idx,:) = mvc_max(group_index(task_idx),:);
    end
end

function mvc = get_mvc(mvc_emg_array, fs, target_sec)
    target_window_size = min(fs * target_sec, length(mvc_emg_array));
    mvc = [];
    for i = 1:size(mvc_emg_array, 2)
        max_mean = -100;
        max_window_start = 1;
        for j = 1: size(mvc_emg_array,1)-target_window_size+1
            temp_mean = mean(mvc_emg_array(j:j+target_window_size-1,i));
            if temp_mean > max_mean
                max_mean = temp_mean;
                max_window_start = j;
            end
        end
        mvc_temp = max(mvc_emg_array(max_window_start:max_window_start + target_window_size-1,i));
        mvc = cat(2, mvc, mvc_temp);
    end
end