Mild exercise early in life produces changes in bone size and strength but not density in proximal phalangeal, third metacarpal and third carpal bones of foals.

Exercise or lack of it in early life affects chondro-osseous development. Two groups of horses were used to investigate the effects of age and exercise regimen on bone parameters of diaphyseal, metaphyseal, epiphyseal and cuboidal bones of the distal limb of Thoroughbreds. One group had exercised only spontaneously from an early age at pasture (PASTEX group), while the other group of horses were exposed to a 30% greater workload through additional defined exercise (CONDEX). Longitudinal data from peripheral quantitative computed tomography (pQCT) were obtained from eight scan sites of the left forelimb (proximal phalangeal (P(p); 1 site), third metacarpal (Mc3; six sites) and third carpal (C(3); one site) bones) of 32 Thoroughbred foals scanned five times from ∼3 weeks to 17 months of age. The primary outcome measures were bone mineral content (BMC), bone area (BA), and periosteal circumference (Peri C) in diaphyseal bone, with cortical thickness (CortTh), volumetric bone mineral density (BMD(v)) and a bone strength index (SSI) also being analysed. At the P(p) site within the model there was a significant effect (P=0.00-0.025) of conditioning exercise increasing bone parameters, except endosteal circumference (Endo C) and BMD(v). The BMC, BA, and SSI of P(p) were significantly greater in the CONDEX than PASTEX groups at 12 and 17 months (P=0.015-0.042) and CortTh at 17 months (P=0.033). At the M55 site of Mc3 BMC, BA and SSI (P=0.02-0.04), and at the M33 site, SSI (P=0.05) were higher in the CONDEX than PASTEX group. The adaptive responses, consistent with diaphyseal strengthening, were more marked in the diaphysis of P(p) than Mc3. In the Mc3, metaphysis, trabecular BMD(v) was less in the CONDEX than PASTEX group, associated with greater bone mineral accretion in the outer cortical-sub-cortical bone in the CONDEX group. There were no significant between-group differences in any epiphyseal or cuboidal bone parameter. Although the early imposed exercise regimen was not intensive, it had significant effects on diaphyseal bone strength, through change in size but not bone density.

[1]  H. Haapasalo Physical activity and growing bone. Development of peak bone mass with special reference to the effects of unilateral physical activity. , 1998, Annales chirurgiae et gynaecologiae.

[2]  K. Tokuyama,et al.  Tomographical description of tennis-loaded radius: reciprocal relation between bone size and volumetric BMD. , 1999, Journal of applied physiology.

[3]  P. R. van Weeren,et al.  Effect of loading on the organization of the collagen fibril network in juvenile equine articular cartilage , 2009, Journal of orthopaedic research : official publication of the Orthopaedic Research Society.

[4]  A. Goodship,et al.  Galloping exercise induces regional changes in bone density within the third and radial carpal bones of Thoroughbred horses. , 1999, Equine veterinary journal.

[5]  P. Clegg,et al.  High-intensity exercise induces structural, compositional and metabolic changes in cuboidal bones--findings from an equine athlete model. , 2008, Bone.

[6]  P. Morel,et al.  Growth curves from birth to weaning for Thoroughbred foals raised on pasture , 2007, New Zealand veterinary journal.

[7]  A. Goodship,et al.  How does exercise intensity and type affect equine distal tarsal subchondral bone thickness? , 2007, Journal of applied physiology.

[8]  P. R. van Weeren,et al.  Evaluation of a new strategy to modulate skeletal development in Thoroughbred performance horses by imposing track-based exercise during growth. , 2008, Equine veterinary journal.

[9]  H. Davies,et al.  Radiographic measures of bone shape in young thoroughbreds during training for racing. , 2010, Equine veterinary journal. Supplement.

[10]  J. Zanchetta,et al.  Mechanical validation of a tomographic (pQCT) index for noninvasive estimation of rat femur bending strength. , 1996, Bone.

[11]  P. R. van Weeren,et al.  Effect of exercise on the proteoglycan metabolism of articular cartilage in growing foals. , 2010, Equine veterinary journal. Supplement.

[12]  M. Doube,et al.  Musculoskeletal responses of 2-year-old Thoroughbred horses to early training. 6. Bone parameters in the third metacarpal and third metatarsal bones , 2005, New Zealand veterinary journal.

[13]  C. Riggs Fractures--a preventable hazard of racing thoroughbreds? , 2002, Veterinary journal.

[14]  P. R. van Weeren,et al.  The influence of exercise during growth on ultrasonographic parameters of the superficial digital flexor tendon of young Thoroughbred horses. , 2008, Equine veterinary journal.

[15]  F. Cicuttini,et al.  Effect of physical activity on cartilage development in healthy kids , 2003, British journal of sports medicine.

[16]  A. Boyde,et al.  Musculoskeletal responses of 2-year-old Thoroughbred horses to early training. 8. Quantitative back-scattered electron scanning electron microscopy and confocal fluorescence microscopy of the epiphysis of the third metacarpal bone , 2005, New Zealand veterinary journal.

[17]  P. R. van Weeren,et al.  Conclusions regarding the influence of exercise on the development of the equine musculoskeletal system with special reference to osteochondrosis. , 2010, Equine veterinary journal. Supplement.

[18]  K. Speed FRACTURES OF THE CARPUS , 1935 .

[19]  E. Firth,et al.  Musculoskeletal responses of 2-year-old Thoroughbred horses to early training. 7. Bone and articular cartilage response in the carpus , 2005, New Zealand veterinary journal.

[20]  Kazuhiko Hayashi,et al.  Effects of physical training on cortical bone at midtibia assessed by peripheral QCT. , 2003, Journal of applied physiology.

[21]  C. Pollitt,et al.  Monitoring distances travelled by horses using GPS tracking collars. , 2010, Australian veterinary journal.

[22]  C L Benhamou,et al.  Bone geometry in response to long-term tennis playing and its relationship with muscle volume: a quantitative magnetic resonance imaging study in tennis players. , 2005, Bone.

[23]  E. Firth,et al.  Musculoskeletal responses of 2-year-old Thoroughbred horses to early training. Conclusions , 2005, New Zealand veterinary journal.

[24]  B. H. Anderson,et al.  Musculoskeletal responses of 2-year-old Thoroughbred horses to early training. 3. In vivo ultrasonographic assessment of the cross-sectional area and echogenicity of the superficial digital flexor tendon , 2004, New Zealand veterinary journal.

[25]  N. Grace,et al.  Musculoskeletal responses of 2-year-old Thoroughbred horses to early training. 1. Study design, and clinical, nutritional, radiological and histological observations , 2004, New Zealand veterinary journal.

[26]  A E Goodship,et al.  Evaluation of a new strategy to modulate skeletal development in racehorses by imposing track-based exercise during growth: the effects on 2- and 3-year-old racing careers. , 2008, Equine veterinary journal.

[27]  L B Jeffcott,et al.  Effects of treadmill exercise on cortical bone in the third metacarpus of young horses. , 1992, Research in veterinary science.

[28]  A. Goodship,et al.  Effects of exercise on tenocyte cellularity and tenocyte nuclear morphology in immature and mature equine digital tendons. , 2008, Equine veterinary journal.

[29]  C. Weaver,et al.  Adaptations to free-fall impact are different in the shafts and bone ends of rat forelimbs. , 2004, Journal of applied physiology.

[30]  Mikko J. Lammi,et al.  Regular joint loading in youth assists in the establishment and strengthening of the collagen network of articular cartilage and contributes to the prevention of osteoarthrosis later in life: a hypothesis , 2000, Journal of Bone and Mineral Metabolism.

[31]  C. McIlwraith,et al.  Joint disease in the horse , 1996 .

[32]  P. R. van Weeren,et al.  Influence of exercise on bone mineral density of immature cortical and trabecular bone of the equine metacarpus and proximal sesamoid bone. , 2010, Equine veterinary journal. Supplement.

[33]  A. Boyde,et al.  Variations in articular calcified cartilage by site and exercise in the 18-month-old equine distal metacarpal condyle. , 2007, Osteoarthritis and cartilage.

[34]  A. Goodship,et al.  Osteoinductive response in the dorsal aspect of the carpus of young thoroughbreds in training occurs within months. , 2010, Equine veterinary journal. Supplement.

[35]  B. Oakes,et al.  Section Modulus is the Optimum Geometric Predictor for Stress Fractures and Medial Tibial Stress Syndrome in both Male and Female Athletes , 2008, The American journal of sports medicine.

[36]  Albert C. Chen,et al.  Site- and exercise-related variation in structure and function of cartilage from equine distal metacarpal condyle. , 2004, Osteoarthritis and cartilage.

[37]  E. Firth,et al.  The response of bone, articular cartilage and tendon to exercise in the horse , 2006, Journal of anatomy.

[38]  J. Wood,et al.  Descriptive epidemiology of fractures occurring in British Thoroughbred racehorses in training. , 2010, Equine veterinary journal.

[39]  D. Frisbie,et al.  A comparative study of articular cartilage thickness in the stifle of animal species used in human pre-clinical studies compared to articular cartilage thickness in the human knee , 2006, Veterinary and Comparative Orthopaedics and Traumatology.

[40]  A. Nixon Equine Fracture Repair , 2019 .

[41]  P. R. van Weeren,et al.  Early exercise advances the maturation of glycosaminoglycans and collagen in the extracellular matrix of articular cartilage in the horse. , 2008, Equine veterinary journal.

[42]  P. R. van Weeren,et al.  Effect of age, exercise and growth rate on bone mineral density (BMD) in third carpal bone and distal radius of Dutch Warmblood foals with osteochondrosis. , 2010, Equine veterinary journal. Supplement.

[43]  P. R. van Weeren,et al.  Quantification of spontaneous locomotion activity in foals kept in pastures under various management conditions. , 2006, American journal of veterinary research.

[44]  P. R. van Weeren,et al.  The influence of strenuous exercise on collagen characteristics of articular cartilage in Thoroughbreds age 2 years. , 2010, Equine veterinary journal.

[45]  C. Kawcak,et al.  Effects of exercise on chondrocyte viability and subchondral bone sclerosis in the distal third metacarpal and metatarsal bones of young horses. , 2008, Veterinary journal.