You can do it in many ways like:
"Back Squat" + " " + "100" //Just concatenating string
exerciseName + " " + variableName //Using concatenating variables in your strings
`Back Squat 100` //Using back ticks or template strings, is the way to go.
`${exerciseName} ${variableName}` //This would be the best way, you can insert many spaces between the variables in this template string