SST Level Up Pathway: 12 Week Strength Development Series The complete Level Up series combines L1, L2 and L3 into a structured 12-week progression designed specifically for swimmers entering and advancing through gym-based strength training. Starting with foundational movement patterns and progressing to barbell loading and percentage-based development, this pathway builds measurable strength, improves force production and aligns every phase with the SST Simple 6 swim mechanics framework.