EMG Sensor with Firgelli L16 and Arduino Uno Question

Projects Programming
2 
void loop()
{
val = analogRead(inPin); // read the input pin
volt =(5.0 * val) / 1023;
val = 255 * (volt / 5);
analogWrite(pwmPin, val);
}

Nonsense. There is no reason to convert the inPin reading to voltage and then convert the voltage back to a ratio. Simply divide the input reading by 4.

The problem is that the EMG muscle sensor's output is way too low.

Then, you need an op-amp to boost the signal to a meaningful range. That is NOT a programming issue.