I am trying to do muscle fatigue analysis, what can be done changes in the code.

with the following code i a trying to do muscle activation and fatigue analysis base on the fft values.

can someone help me with the code. what am i doing wrong and what changes can be done for the analysis

%% Import Data from TXT files
files = dir('*.txt');     % Returns all the files and folders in the directory
fileTable = struct2table(files);
numOfFiles = height(fileTable);

for k = 1:numOfFiles
    if strfind(fileTable.name{k}, 'Fatigue')
        secfiles{k} = fileTable.name{k};
    end
end
allfiles = secfiles(~cellfun(@isempty,secfiles(:,1)),:);
masterData = struct;
for j = 1:length(allfiles)
    file_info(:,j) = split(allfiles(j), "_"); 
    masterData(j).group = file_info(1,j);
    masterData(j).muscle = file_info(2,j);
    masterData(j).trial = extractBefore(file_info(4,j),'.');
    impFatigueA = importdata(allfiles(j)); 
		
		end
%%
% Fatigue Data
impFatigueA = importdata('Fatigue_A.txt');
impFatigueK = importdata('Fatigue_K.txt');
impFatigueZ = importdata('Fatigue_Z.txt');
%impMVICT2 = importdata('G2_Tricep_MVIC_2.txt');

%% Removing the DC Offset from the Signal %%

impFatigueA2 = detrend(impFatigueA); % detrend removes the mean value or linear trend from a vector or matrix. 
impFatigueK2 = detrend(impFatigueK); % detrend removes the mean value or linear trend from a vector or matrix. 
impFatigueZ2 = detrend(impFatigueZ);

 %% Rectifcication of the Signal 
 
 impFatigueA3 = abs(impFatigueA2);
 impFatigueK3 = abs(impFatigueK2);
 impFatigueZ3 = abs(impFatigueZ2);
 
 %% Creating the Envelope of the EMG Signal %%

[b,a]=butter(5,2.5/1000,'low'); % low pass filter to cut off frequency at 10Hz, using a 5th order filter and a samppling frequencyt of 1000Hz.
impFatigueA4=filtfilt(b,a,impFatigueA3);
impFatigueK4=filtfilt(b,a,impFatigueK3);
impFatigueZ4=filtfilt(b,a,impFatigueZ3);

%% fft plot for impFatigueA4 %%
Fs=1000;
L=length(impFatigueA4);
t=L/Fs;
x=impFatigueA4;
Y = fft(x);
P2 = abs(Y/L);
P1 = P2(1:L/2+1);
P1(2:end-1) = 2*P1(2:end-1);
f = Fs*(0:(L/2))/L;
plot(f,P1) 
title('Frequency Spectrum Plot')
xlabel('f (Hz)')
ylabel('|P1(f)|')

Error i am getting.

Index in position 1 exceeds array bounds (must not exceed 3).

Error in untitled (line 17)
    masterData(j).trial = extractBefore(file_info(4,j),'.');