This paper investigates the design of a soft elbow exosuit capable of providing supplemental lifting assistance by reducing muscle activity of the bicep muscle. The aim is to improve the efficiency and endurance of workers who are tasked with repetitive lifting. The design consists of an array of pneumatically pressurized soft actuators, which are encased in nylon fabric that allows for a high force-to-weight ratio of 211.SN/g. An analytical model governing the bending behavior of two consecutive actuators and torque generated by the exosuit is developed, with test results showing less than 10% error from the theoretical model. An elbow joint torque value of 27.6N.m is achieved at 300kPa, which is comparable to the 30N.m maximum set by OSHA requirements in the USA. Further testing with a healthy participant is performed using surface electromyography (sEMG) sensors and a motion capture system to assess the capabilities of the exosuit to provide active assistance to the bicep during isometric and concentric contractions. Measurable assistance to lifting is observed with minimal obstruction to the user's range of motion for all experiments.