The influence of exercise during growth on ultrasonographic parameters of the superficial digital flexor tendon of young Thoroughbred horses.
BACKGROUND
Conditioning by early training may influence the composition of certain musculoskeletal tissues, but very few data exist on its effect during growth on tendon structure and function.


OBJECTIVE
To investigate whether conditioning exercise in young foals would lead to any ultrasonographically detectable damage to the superficial digital flexor tendon or an increase in cross-sectional area (CSA).


METHODS
Thirty-three Thoroughbred foals reared at pasture were allocated to 2 groups: control (PASTEX) allowed exercise freely at pasture; and CONDEX, also at pasture, began conditioning exercise from mean age 21 days over 1030 m on a purpose-built oval grass track, for 5 days/week until mean age 18 months. Foals were observed daily, and underwent orthopaedic examination monthly. Ultrasonographic images of the superficial digital flexor tendon (SDFT) at the mid-metacarpal level of both forelimbs were obtained in all foals at ages 5, 8, 12, 15 and 18 months. CSA was validated (r(2) = 0.89) by determining CSA from digital photographs of the transected SDFT surface from 12 of the horses necropsied at age 17.1 months.


RESULTS
here was no clinical or ultrasonographic evidence of tendonopathy in either group and the greatest increase in mean CSA in both groups occurred between age 5 and 8 months. Across all age categories, there was no significant difference in mean CSA between the left and right limbs, or colts and fillies; there was a trend towards a larger CSA in the CONDEX group (P = 0.058).


CONCLUSIONS
There was no conclusive evidence for a structural adaptive hypertrophy of the SDFT, probably because the regimen was insufficiently rigorous or because spontaneous pasture exercise may induce maximal development of energy storing tendons.


CONCLUSIONS
A moderate amount of early conditioning exercise against a background of constant exercise at pasture is not harmful to the development of the flexor tendons.
Moffat
P A
PA
Institute of Veterinary and Animal Biomedical Sciences, Massey University, Palmerston North, New Zealand.
Firth
E C
EC
Rogers
C W
CW
Smith
R K W
RK
Barneveld
A
A
Goodship
A E
AE
Kawcak
C E
CE
McIlwraith
C W
CW
van Weeren
P R
PR
D000222:Adaptation, Physiological; D000818:Animals; D000831:Animals, Newborn; D005260:Female; D006734:Horse Diseases / Q000453:epidemiology / Q000517:prevention & control; D006736:Horses / Q000254:growth & development / Q000502:physiology*; D006984:Hypertrophy / Q000453:epidemiology / Q000517:prevention & control / Q000662:veterinary; D008297:Male; D010805:Physical Conditioning, Animal / Q000009:adverse effects / Q000502:physiology*; D011897:Random Allocation; D013708:Tendon Injuries / Q000453:epidemiology / Q000517:prevention & control / Q000662:veterinary; D013710:Tendons / Q000000981:diagnostic imaging* / Q000254:growth & development*; D014463:Ultrasonography