Charley horse

Charley horse: cãibra na perna ou no pé

“…had to stop and rest because of a charley horse in his leg…” (www.merriam-webster.com)

Synonyms: cramp, crick, kink, spasm

Can't cut the mustard

Can't cut the mustard: diz-se de quem não consegue lidar com problemas ou dificuldades

“If she can't cut the mustard, we'll have to find someone else to do the job.” (www.thefreedictionary.com)