Strength training improves overall health, well-being, physical appearance, and sports performance, with training programs specifying variables such as sets, repetitions, rest time, weight, and tempo. The repetitive nature of strength training, typically performed at fixed tempo, has made it challenging to develop entertaining exergames for common strength training exercises. We present StrengthGaming, which uses scaling and shuffling technique to provide tempo variations to strength training while preserving the training volume and training goals. It affords game designers more flexibility in designing strength training-based exergames. We developed a prototype game, inspired by FlappyBird, that uses a wearable orientation sensor to track the repetition tempo to control a flying character, using both fixed tempo design and dynamic tempo design. Results from our 24-person user study showed that dynamic tempo was significantly more entertaining than fixed tempo (ptextless0.01), and was preferred by participants.