The phrasal verb "bulk up" is predominantly used in informal contexts, especially within conversations related to fitness and bodybuilding. It is often employed to describe the process of gaining muscle mass, usually through a combination of increased calorie intake and weight training. "Bulk up" is frequently found in fitness circles, gym discussions, and sports commentaries, where individuals aim to increase their size and strength. While it's most commonly heard in casual settings, it can occasionally appear in more formal contexts related to health or nutrition, but usually with clarification or explanation. The phrasal verb suggests not just any increase in size, but a specific focus on building muscle, and is less about fat gain or weight gain in general.
B1
PreIntermediate
1. To gain weight, particularly by adding muscle mass through diet and training.
He's been trying to bulk up before the start of football season.
She bulked up over the winter to prepare for her bodybuilding competition.
2. To increase the size or volume of something; to make something bigger or thicker.
They need to bulk up the report with more statistics.
The company is looking to bulk up its workforce in response to increased demand.