Is there value in checking bone turnover markers in response to weight training to guide bone building?

Bone Turnover Markers in Response to Weight Training: Limited Clinical Value

There is currently insufficient evidence to support the routine use of bone turnover markers to guide bone building in response to weight training. 1

Understanding Bone Turnover Markers

Bone turnover markers (BTMs) are biochemical products that reflect the metabolic activity of bone. They fall into two main categories:

• Bone formation markers:

  • N-terminal propeptide of type I procollagen (PINP)
  • Bone-specific alkaline phosphatase (B-ALP)
  • Osteocalcin

• Bone resorption markers:

  • C-telopeptide of type I collagen (CTX)
  • N-telopeptide of type I collagen (NTX)

Evidence Against Routine Use

The American Society of Clinical Oncology guidelines explicitly state that "until the time that properly defined marker studies demonstrate clinical utility, the use of biomarkers to guide or monitor bone-modifying agent therapy is not recommended outside of a clinical trial." 1 While this recommendation was made in the context of cancer treatment, the underlying principle applies to weight training as well.

Several limitations make bone turnover markers problematic for monitoring response to weight training:

1. High variability: BTMs are subject to significant within- and between-patient variability 2, 3

   • Diurnal variations (levels change throughout the day)
   • Affected by food intake (resorption decreases after feeding) 4
   • Seasonal changes
   • Menstrual cycle effects

2. Lack of site specificity: BTMs reflect whole-body bone metabolism rather than changes at specific skeletal sites that might be targeted by weight training 1

3. Non-specific changes: BTMs can be affected by numerous factors unrelated to exercise:

   • Recent fractures (all markers increase for several months) 4
   • Age
   • Gender
   • Kidney or liver disease 1

Limited Clinical Applications

While BTMs have some established clinical uses, guiding bone-building exercise programs is not among them:

• BTMs are useful for monitoring pharmaceutical treatments for osteoporosis 3, 5
• They can help identify poor medication adherence 3
• They may help detect secondary causes of high bone turnover (e.g., bone metastases) 4

However, a systematic review concluded that "there was insufficient evidence to inform the choice of which bone turnover marker to use in routine clinical practice to monitor osteoporosis treatment response." 6

Practical Considerations

If you still wish to explore BTM testing despite these limitations:

1. Standardize collection:

   • Collect blood samples after overnight fasting
   • Collect at the same time of day for serial measurements 1

2. Use consistent methodology:

   • Use the same laboratory and assay method
   • Understand the least significant change values for the specific markers

3. Focus on established markers:

   • PINP for formation
   • CTX for resorption
   • These are recommended by international organizations for clinical use 5

Alternative Approaches for Monitoring Bone Health

Instead of relying on BTMs to guide weight training, consider:

1. Dual-energy X-ray absorptiometry (DEXA) for baseline and follow-up bone mineral density measurements

   • More reliable for long-term monitoring of bone changes
   • Should be performed on the same equipment using consistent reference standards 1

2. Fracture risk assessment tools like FRAX to estimate 10-year probability of fracture 1

3. Progressive resistance training programs based on established exercise principles rather than BTM results

In conclusion, while bone turnover markers provide insight into bone metabolism, their high variability and lack of site specificity make them unsuitable for guiding weight training programs aimed at bone building. Focus instead on established progressive resistance training protocols and periodic bone density measurements to assess long-term changes in bone health.