Case Study: A Longitudinal Observation of Bone Density and Strength in Twins in Their 60s

Abstract

This report presents a longitudinal observation of two female twins in their 60s, hereafter referred to as Sophie and Chloe, examining the effects of different strength training approaches on bone density over several years. Sophie engaged in a structured, progressively overloaded barbell strength training program under coaching supervision, while Chloe participated in light, machine-based resistance training designed to support muscle and bone health and maintained general physical activity. Sophie’s bone density improved from osteoporosis to osteopenia, whereas Chloe’s bone density declined from osteopenia to osteoporosis. These results underscore the potential impact of long-term, progressive strength training on bone health in older adults.

Introduction

Osteoporosis and low bone density are significant risk factors for fractures, loss of independence, and reduced quality of life in older adults. Characterised by reduced bone mineral density (BMD) and deterioration of bone microarchitecture, osteoporosis affects millions worldwide and is particularly prevalent in postmenopausal women due to hormonal changes associated with decreased estrogen levels (World Health Organization, 2003).

Mechanical loading plays a critical role in bone adaptation, as described by the principles of Wolff’s Law, which states that bone remodels in response to the forces placed upon it. Resistance training, particularly high-load and weight-bearing exercise, has been shown to stimulate osteogenesis by increasing mechanical strain on bone tissue (Turner & Robling, 2003). In contrast, low-load or non-weight-bearing activities may provide insufficient stimulus to significantly improve bone density.

A growing body of evidence supports the use of progressive resistance training as an effective intervention for improving or maintaining BMD in older adults. Notably, the LIFTMOR Trial demonstrated that high-intensity resistance and impact training significantly improved bone density and functional performance in postmenopausal women with low bone mass (Watson et al., 2018). These findings challenge earlier concerns regarding the safety of heavy lifting in osteoporotic populations and highlight the importance of appropriate supervision and program design.

Despite this evidence, much of the existing literature is derived from controlled trials with relatively short durations, typically ranging from several months to one year. Longitudinal observations extending over multiple years in real-world settings remain limited. Furthermore, few studies have examined individuals with shared genetic backgrounds, such as twins, which may provide valuable insight into the relative influence of environmental and behavioural factors on bone health.

This case study explores the long-term effects of two distinct resistance training approaches in female twins in their 60s. By comparing structured, progressively overloaded barbell training with machine-based resistance exercise and general physical activity, this report aims to provide an insight into how training modality, intensity, and consistency influence bone density outcomes in older adults.

Participants

Sophie and Chloe are female twins in their 60s. Pseudonyms are used to maintain participant confidentiality. Both participants underwent routine bone density scans over the study period. Neither participant had any conditions beyond those described that would independently affect bone density.

• Sophie: Engaged in supervised, structured barbell-based strength training with progressive overload. Chose not to take medication for osteoporosis.

• Chloe: Participated in machine-based resistance training designed to support muscle and bone health for older adults, alongside general physical activity and travel.

Methods

Bone Density Measurement

Bone density was assessed using dual-energy X-ray absorptiometry (DEXA) of the left femoral neck. T-Scores were interpreted as follows:

• Normal: > -1

• Osteopenia: -1 to -2.5

• Osteoporosis: < -2.5

Training Protocol

Sophie:

• Barbell-based compound strength training program

• Coaching-first approach emphasising proper technique and movement patterns

• Progressive overload applied systematically over 4 years

• Consistent weekly attendance

• Program coordinated with allied health professionals to ensure safety and optimise outcomes

Chloe:

• Machine-based resistance training with controlled, low-impact exercises

• Program aimed at maintaining functional strength and supporting bone health

• General physical activity maintained through travel and daily life

Results

Sophie – Bone Density and Training Outcomes

Left Femoral Neck T-Scores:

• Nov 2022: -3.6 (Osteoporosis)

• Feb 2023: -3.22

• Feb 2024: -2.9

• Mar 2026: -2.3 (Osteopenia)

Sophie progressively increased strength over the 4-year period, demonstrating functional gains alongside improvements in bone density. No medication was taken during this period.

Chloe – Bone Density Outcomes

Left Femoral Neck T-Scores:

• Mar 2016: -1.92 (Osteopenia)

• Oct 2023: -2.6

• Nov 2024: -2.72

• Feb 2026: -2.7 (Osteoporosis)

Chloe’s bone density declined from osteopenia to osteoporosis, despite remaining generally active and completing machine-based resistance exercises.

Discussion

This case highlights several key observations:

1. Structured, progressively overloaded barbell training is associated with measurable improvements in bone density in older adults, even in individuals initially diagnosed with osteoporosis.

2. Consistency and coaching support are critical, including attention to technique, program design, and progression.

3. Machine-based resistance training and general activity, while beneficial for overall health, may not produce the same degree of improvement in bone density when compared to structured, progressive overload training.

4. Both participants were in their 60s, emphasising the potential for bone adaptation later in life.

5. This case is a rare longitudinal observation involving twins, providing a unique perspective on genetic and lifestyle influences on bone density.

Limitations

• Small sample size (n = 2); results cannot establish causation.

• Findings may not generalise to all populations, although they provide insight into potential outcomes of structured strength training.

• Chloe’s physical activity and resistance training were not as closely monitored as Sophie’s, which may have influenced results.

Conclusion

This longitudinal observation demonstrates that structured, coached, progressively overloaded strength training can significantly improve bone density in older adults, even without medication. The twin comparison illustrates the potential variance in bone density outcomes based on training type and intensity. These findings support the use of long-term, progressive strength training as a key intervention for bone health, particularly in aging populations.

References

Turner, C. H., & Robling, A. G. (2003). Designing exercise regimens to increase bone strength. Exercise and Sport Sciences Reviews, 31(1), 45–50. https://doi.org/10.1097/00003677-200301000-00009

Watson, S. L., Weeks, B. K., Weis, L. J., Harding, A. T., Horan, S. A., & Beck, B. R. (2018). High-intensity resistance and impact training improves bone mineral density and physical function in postmenopausal women with osteopenia and osteoporosis: The LIFTMOR randomized controlled trial. Journal of Bone and Mineral Research, 33(2), 211–220. https://doi.org/10.1002/jbmr.3284

World Health Organization. (2003). Prevention and management of osteoporosis: Report of a WHO scientific group. World Health Organization.