I often only have a short amount of time to squeeze in exercise so when I do an online workout it needs to be quick, effective and fun. Personal trainer Britany Williams always ticks all three boxes with the workouts she posts on her Instagram account. She often uses compound exercises (working multiple muscle groups at once), allowing you to work your whole body in less time. Like me, the Sweat coach is a mom to young children so she understands the time constraints parents face. Latest Videos From Here are three of her workouts I do on repeat. My favorite Britany Williams workout for arms This 15-minute arms workout features just three dumbbell exercises—the single-arm shoulder press, single-arm row and skull crusher—ticking off a push, a pull and an isolation move for the triceps on the back of your arms. You may like This neat little circuit not only works your upper body but also challenges your core. In a kneeling position, your abdominal muscles will work hard to stabilize you, and the skull …