For what I get, I think the answer is
Because it say "during his workout yesterday, Anthony pushed himself by lifting heavier weights." Which means he lifted a thing that he never did before, means he overload.
Anthony is feeling OVERLOAD
I would say progression.
Also known as the principle of progressive lifting of the load, the principle of overload is related to the adaptations suffered by the organism as a result of the training stimuli (physical effort). In this principle there is a regular and progressive increase of the (total) exercise load that will allow the desired improvement of performance. Based on this principle, Anthony struggled to lift heavier weights than the weights he was lifting. This is because it is progressively increasing the exercise load. For that reason, he felt good, but his muscles were sore because they were not used to this weight.
I think it's the answer, tell me if it's not
The correct answer is - overload.
The overload principle is the principle that states that producing the result continuously, exercise should be more challenging over the time period of any exercise program.
Lifting heavyweights in the strength training programs, muscles become sore due to challenging weight lifting by adding heavyweights in bars. Anthony is working on his strength training that is based on the overload principle by pushing himself.
Thus, the correct answer is - overload.