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About Threshold Training
Train With Intention.
Build Lifelong Performance.
Threshold Training was built on a simple belief: training should be structured, measurable, and grounded in how the body actually adapts. Not driven by trends. Not reduced to aesthetics. And not based on random intensity.
This is training for athletes who care about the why—and who want to improve for the long term.
Our Philosophy
At Threshold Training, performance is built through intention. Every session has a purpose. Every phase fits into a larger system. Progress is measured, not guessed.
We focus on developing the full spectrum of athletic qualities:
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Strength and power
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Aerobic capacity and efficiency
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Durability and recovery
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Long-term resilience
Rather than chasing fatigue or short-term results, our methodology emphasizes appropriate intensity, consistent exposure, and sustainable progression. This approach allows athletes to train hard when it matters—and recover well enough to continue improving.
Threshold Training is led by Spencer Mossburg, a Certified Strength and Conditioning Specialist (CSCS), CrossFit Level 1 Coach, USA Weightlifting Level 1 Coach, and HYROX Performance Coach.
Spencer’s approach to coaching is shaped by a broad athletic and professional background. As a multi-sport athlete, he developed an early appreciation for varied movement, competition, and long-term athletic development. That curiosity eventually led him to the weight room, where he became deeply invested in strength and power training—and later into the study of aerobic development, conditioning, and energy systems.
Rather than committing to a single methodology, Spencer pursued education across multiple training disciplines to understand what each does well—and where each falls short. His certifications and experience span Olympic weightlifting, CrossFit, endurance and aerobic development, and hybrid performance models such as HYROX. This exposure allows him to coach athletes with a complete perspective, rather than forcing them into one narrow system.
Through Threshold Training, Spencer integrates that practical experience with evidence-based exercise science principles to create structured, intentional programming. The goal is not to train harder for its own sake, but to apply the right stimulus at the right time—building strength, power, aerobic capacity, and durability in a way that supports long-term performance.
Whether working with athletes in person in Chattanooga or remotely through structured training programs, Spencer’s coaching is grounded in education, clarity, and consistency. Every recommendation has a purpose, and every phase is designed to move athletes closer to sustainable, measurable progress.