Publishing Author : Alan Gardner, PGD A. PHYS, MDIP, DipMgmt
Date Published : 2015
The hamstring group of muscles are extensively used for generating the forward movement
and for the jumping action in canine Agility. I set out to understand how much force is used in
executing the jumping action in Border Collies and what might happen if this muscle group is
repetitively overloaded. This has implications in Agility as the amount of training and
competition continues to increase, placing ever higher demands on the canine athletes. Five
case studies were used, all over 5 years old and training / in competition since at least 2 years
old. In each case the hamstring tendon of origin was treated on a specific limb with
therapeutic ultrasound, deep-friction-massage and stret
An average Border Collie will stand some 50 – 60
cm high and have a body mass of between 15 – 20
kgs. This breed is categorised by their high
motivational drive, speed and turning ability (1)
which makes them the most popular breed for
Typically a large Agility dog (>45cm at the
shoulder) competing in the UK, training twice a
week and doing 48 competition days a year will
hurdles of 65cm height per annum.
Speed and jumping ability on an Agility course
are the two of the most important competitive
Speed is influenced by limb strength which
dictates stride length (2) (3). Stride length coupled
with frequency determine velocity.
Jumping has 5 phases (4) :
3. Aerial phase
4. Landing phase
During the take-off the jump trajectory is
determined and the hind limb musculature is used
together with energy release from elastic tissues to
provide the necessary power.
The hamstring group are an important muscle
group employed to execute this phase (5)2
are the main hip extensor muscles which generate
Average of 15 hurdles per round and 4 courses per
day and per training session. 3 competitive weekends
(2 days) per month for 8 months per annum.
much of the dogs forward thrust (i.e. speed) in
locomotion (7). Therefore this muscle group
deserves particular attention in optimising Agility
Five competitive Border Collies with (nonpainful)
tightness in the hamstring tendon of
origin area were treated using a course of
therapeutic ultrasound, deep friction massage
(DFM) and stretching. The aim was to understand
if this tension could be reduced, natural range-ofmotion
(ROM) improved with a potential
corresponding improvement in athletic Agility
Canine Hamstring Muscle and
This muscle group comprises the bicep femoris,
semitendinosus and semimembranosus, with
perhaps the 2 former playing a more important
role in propulsion by extending the hip and
. Williams et al (8) studied the muscle
weight, force and work of the greyhound (mass
31.8 ± 2.6 kg), see table 1.
Notwithstanding primary canine and equine structural
Semimembranosus being more significant for stifle
stabilization, hock extension and hip adduction
Figure 1 – Dog demonstrating full
extension over a 65cm hurdle
% of mass
Biceps femoris 485 960 N 50 W 1.4 –
Semitendinosus 196 360 N 20 W 0.6 –
Semimembranosus 170 240 N 18 W 0.5 –
Table 1- Comparing the Greyhound hamstring muscle
weight, force, work and percentage of body weight
An important finding compared to a similar study
(9) is that Greyhound biceps femoris and
semitendinosus show larger amounts of
hypertrophy (approximately double in size)
whereas semimembranosus shows little
difference. Applying these calculations to an
average Border Collie5
, we can estimate the
potential muscle sizes and output in this breed
(see table 2).
% of mass
Biceps femoris 105 –
Semitendinosus 45 –
4 – 7
Semimembranosus 75 –
Total (per limb) –
Total (both hind
Total per kg of body
1 kg 54 –
2 W –
Table 2- Theoretical calculation of a Border Collie
hamstring muscle weight, force and work
Single total body weight / single muscle weight
Without this hypertrophy
Pfau (4) calculated 45 N/kg of body Mass (BM) in
the landing forelimbs of an Agility dog, which
means a similar force will be required to execute
the take-off. These factors mean that the
hamstrings are working at 70 – 85% of their
theoretical maximum force output for the dog to
negotiate a 65cm hurdle (based on calculations in
Theoretically the canine centre of gravity of an 18
kg Border Collie is 11:9 and 9:9 kgs (front: rear)
and 9:9 (side: side). This makes a theoretical even
loading to one hind limb of 3.6 kgs. Running and
jumping activities can make muscles susceptible
to tearing and pulling just like humans (10). Also
we noted that changes can exist in the tendon
without pain (11).
To overload one hamstring group of muscles (i.e.
>100%) in our example above, would only take a
shift to 4.2:3.0 for overloading the hamstrings
tendons (on one side) and the potential for
collagen catabolism (12).
Rounded up / down
Figure 2 – The anatomy of a muscle and
Hamstring injuries usually occur at the
musculotendinous junction (13) as this interface is
subject to stress concentration (14). This gradual
deterioration of a tendon (tendonitis or
typically affects the tendon of
origin sites at the ischial tuberosity.
Sports injuries of this type are common and well
documented in humans (15), typically resulting
from non-optimal gait mechanics, muscular
imbalances, or improper training (16). IAAF (17)
provides a theoretical pathway of a sports-induced
injury, with a possible process for tendinopathy in
the Agility dog.
Tendons transmit force from the muscle to bone
and absorb external forces to limit muscle damage
(18). They are white and have a fibro elastic
texture and consist of 90 – 95% tenoblasts and
tenocytes. The remainder of the tendon is formed
from chondrocytes, synovial cells, vascular and
smooth muscle cells (19). The dry mass is about
30%, with some 65 to 80% of this being type I
Tendon injury and healing
Tendons have a lower metabolic rate than muscle
and their oxygen consumption is some 7.5 times
NHS (2013) differentiates tendonitis as ‘inflammation
of a tendon’ and tendinopathy as ‘the gradual
deterioration of a tendon’
The remaining 5% of collagens consisting mainly of
types III and V. Other constituents include elastin
lower. These factors coupled with their welldeveloped
anaerobic energy generation are
essential to reduce the risk of ischemia while
carrying heavy loads and maintaining tension for
However this also results in slower healing after
injury which can be an acute trauma (i.e. rupture)
or chronic (20) tendinopathy – “tendon
degeneration with a complete absence of
inflammatory cells” (21). This type of injury
involves repeated stretching of the tendon (22)
between 4 and 10% (see table 3) and comprises
both intrinsic and extrinsic9
Less than 4% Behaves in elastic fashion returns
4 – 8% Microscopic failure – may not
allow enough time for repair (24)
8 – 10% Macroscopic failure (Intrafibril
Table 3- Effect of stretching on the tendon
Tendon healing can be classified in the stages of
inflammatory (up to 3 days), proliferative (3 – 24
days) and remodelling. Features of the healing
process at the remodelling (chronic) stage include
the formation of scar tissue and a decline in
tenocyte metabolism and tendon vascularity (25).
Examples of intrinsic factors are tendon vascularity,
age, gender, body weight and height. Extrinsic factors
include changes in training pattern, poor technique,
previous injuries, and training on hard, slippery or
Application of Human Based
Understanding of tendinopathy has been presented
primarily on human based research. How does this
translate to understanding of the same issue in the
Warden (26), argues that using animal models’
represents “an efficient and effective means of
advancing understanding to develop tendon
changes that are consistent with human
These models provide tendon information which
• Collagen fibre arrangement
• Cellular composition
• Tissue level properties
This allows us to both understand the
pathophysiological pathways and propose
treatments based on the current published
literature with the following limitations:
1. Current animal models include rat
supraspinatus / patellar and rabbit flexor
digitorum profundus. Dogs are not
generally used due to size and cost of the
2. The differences between the bipedal and
3. Human tendinopathy occurs at multiple
sites possibly resulting in different
10 Deep Friction Massage
4. A discordance in results which mean
animal models may not be useful for
advancing tendinopathy research (27).
However, Warden (26) argues that a lack
of studies and clinical tests mean they
should not be discounted either.
5. Differences in pain perception. Dogs will
hide the more obvious pain signals which
makes it more difficult for humans to
recognise when the dog is hurting (28).
Therapeutic Ultrasound (29) coupled with DFM10
is suggested for chronic tendonitis (30) (31) (32)
complemented by stretching, which “adapts the
tendon to the mechanical loads placed on it, and
prevents the tendons from incurring (further)
injuries” (19). ‘Mills’ manipulation (33) is
recommended for this stretching. However as this
technique involves potential to “cause traumatic
arthritis and is not a comfortable procedure for
the patient” (34), eccentric stretching was
substituted for the canine patient.
Therapeutic Ultrasound was administered to help
break down scar tissue and re-orientate collagen
fibres (35). DFM and stretching was applied to
stimulate tissue adaptation (33). Additionally,
owners were requested to carry out rear limb
“repetitive low-intensity stretching to stimulate
tissue elongation” (36) i.e. ‘bicycle movements’
each day. This aim of this exercise is to help with
gait pattern retraining and improvement of joint
ROM (37) (38). For each case, 6 individual
treatments sessions were held (39) (40), see table
Session 1 2 3
11 4 5 6
Evaluation √ X X X X √
Ultrasound √ √ √ X X X
Massage X X X √ √ √
Stretching X X √ √ √ √
Table 4- Treatment Plan Schedule
Overview and Benefits
Ultrasound (sound waves) are a form of
mechanical energy (41). When the sound waves
pass through tissue the energy is transferred
through dissipation and attenuation (42). This
results in the both thermal and non-thermal
physical effects (35) which improve tensile
strength and energy absorption of the tendon (43).
• Thermal – heating tissue to 40 – 45◦C for 5
minutes accelerates both enzymatic
(biological catalysts), microcirculation (44)
and metabolic biochemical reactions within a
• Cavitation – formation of tiny (1µm) bubbles
which oscillate and produce reversible
permeability changes in cell membranes (46).
11 After session 3, owner carried out daily bicycle
movements on hind limb, each session consisted of 10
repetitions forward and 10 in reverse.
• Acoustic streaming – radiation torque causes
circulatory flow (microstreaming), increasing
cell membrane permeability and altering the
rate of ion diffusion (47).
• Standing waves – pressure pattern causes
stasis of cells in blood vessels at pressure
The frequencies used in therapy can be divided
into shortwave (1.0 and 3.0 MHz) and longwave
The primary differences in these frequencies are
outlined in table 5.
Wavelength λ 1.5 mm 0.5 mm 300 mm
X 20 of
Thermal Effects Deep (50)
Effects Yes Yes Yes
Effect on bone Can cause damage
Table 5- Comparing short and long wave ultrasound
12 1MHz = 1 million cycles per second, 1 KHz = 1
thousand cycles per second
Figure 3 – Longwave
As the ultrasound was primarily focused at the
musculotendinous junction, close to the ishiatic
tuberosity, longwave frequency was chosen to
avoid potential “thermal damage to the bone that
can compromise its strength for extended
Where applicable, the area for treatment was
shaved (45) gel put onto the area and applied
continuous (LW) Ultrasound applied:
• 500 mW for 5 minutes for the first
• 100 mW for 5 minutes for subsequent
Deep Friction Massage
Overview and Benefits
Benefits of massage include increasing blood flow
and oxygen supply, removal of waste products
and mobilising adhesions (37). For the treatment
of tendinopathy, “manually applied controlled
trauma to a tendon may actually induce the
production of the fibroblasts and specialized
proteins necessary for regeneration” (55).
Additionally massage has a calming effect on the
Hourdebaigt (57) lays out a treatment for scar
tissue. Low constant or repetitive load is
recommended (45) for the amount of applied
pressure during treatment. This results in tissue
elongation by biological creep. This plays a role
in conventional tissue expansion by generation of
new tissue due to a chronic stretching force (58).
Overview and Benefits
Stretching is recommended in dog rehabilitation
to improve range of movement (45) and to reduce
tightness in tendons (38).
Figure 4 – Administering ultrasound
Figure 5 – Applying deep friction massage
Figure 6 – Stretching in standing
Stretching improves flexibility by increasing the
number of sarcomeres (59). Increased flexibility is
important for injury prevention for the hamstring
and adductor group of muscles (60). Of the 5
static stretches (61), passive stretching is the most
applicable for the canine patient “because of the
inability to verbally communicate instructions to
the patient” (45).
5 rules for proposed for stretching the canine
1. Muscles should be warm (63).
2. Muscles must be fully relaxed with dog in
recumbent position where possible.
3. Joint needs to be stabilised.
4. Stretching the muscles using a straight
5. Hold stretch for 30 seconds, engaging
both elastic and non-elastic fibres.
This process is claimed to avoid concentric,
eccentric and isometric contractions. Some
limitations in this approach were noted:
a) Not all dogs are comfortable in the recumbent
position and this cannot be ‘requested’ (64).
b) Eccentric training is a potentially successful
treatment option in rehabilitation of chronic
tendinopathic dysfunction (16).
These rules coupled stretching of the opposing
muscles (quadriceps group) were carried out in all
the treatments (61).
Evaluation and Measuring the
1) Hamstring Stretch (Extension)
The dogs were stood square, with the hips
supported to avoid rotation. Individually both hind
limbs were extended cranially as far as the dog
was comfortable, without inducing a passive
assisted stretch (see figures 8 & 9). At that point
the paw was placed on the ground and the
distance from the rear of the front paw measured.
The measurement was made 3 times to improve
Figure 8 – Demonstrating measuring from the tip of
the front feet to the tip of the rear feet
Figure 7 – Stretching in recumbency
Figure 9 – Demonstrating measuring of the
hamstring extension. The tip of the rear foot is
again used for the calculation
2) Static Weight Distribution
5 measurements using bathroom scales was
quantitatively estimated with the mean reported
3) Gait Analysis
A treadmill13 (66) was used at a walking pace of
2.5 – 3.0 km/h14. The dogs were recorded in both
real time and slow motion using a Sony Action
Cam HDR-AS15. Quantitative calculations based
on the Jena study (3) include:
1. Stride length
2. Relative stride length
3. Stride duration
4. Stance phase duration
For benchmarking, the closest dog to a Border
Collie in the Jena study was the Beaded Collie.
The average relative rear-limb stride length for
this breed at a walk is given at 1.5 (at 0.97 m/s
Swing phase duration (in all case studies) returned
a consistent mean value of 0.25 seconds for all the
5 case studies in this report, which agrees with the
Qualitative observations (67) including factors
such as obvious lameness (68) and foot placing
were made by visual interpretation of normal and
slow video replay.
Our study set out to understand could “tension (in
the hamstring tendons) be reduced and the
natural range-of-motion (ROM) (be) improved by
the application of therapeutic ultrasound, deep
friction massage and stretching”.
By using these modalities, we aimed to restart the
healing process as laid out in the section on
‘tendon injury and healing’ and improve the
subsequent repair. The 3 modalities addressed
these healing factors (25):
(i) Therapeutic Ultrasound to reduce scar
Therapeutic Ultrasound influences the
remodelling (49) as well as promoting stronger
and more elastic scar tissue. This is due to an
improvement in collagen organization with
collagen fibres (69).
(ii) DFM to increase tendon vascularity
Angiogenesis, the physiological process through
which new blood vessels form from pre-existing
vessels, can be improved by massage (70).
Additionally massage provides beneficial effects
by increasing blood flow to the degenerative
(iii)Stretching to increase tenocyte
Stretching, increases mechanical loading and
produces growth factors. Increases in tendon fibre
14 Depended on how comfortable the dog was to
perform a steady and controlled walk.
diameter and mechanical strength are derived
through growth factors–beta 1 (TGF-β1) and
insulin-like growth factor 1 (IGF-1) which
promote collagen synthesis and tenocyte
These factors led to the following measurements
and observations from the 5 case studies:
(1) Quantitative (measured) improvement
in hamstring extension
Figure 10 demonstrates the respective
improvements in hamstring extension for the
limbs specifically outlined in the case studies.
Generally the lower the ability to stretch the
hamstring (in extension) to start, the greater the
(2) Qualitative (visual) improvement in
rear limb movement and fluidity
Table 6 shows the lameness (68) score before and
after the treatments. 3/5 were given an improved
score. The lack of improvement in CS1 can be
explained by chronic arthritis which was not
treated as part of this study. The anomaly is CS5,
15 Dogs without osteoarthritis
considering the improvement seen in hamstring
Pre-Assessment Post Evaluation
CS1 3 3
CS2 3 1
CS3 2 1
CS4 2 1
CS5 2 2
Table 6 – Lameness score pre and post treatments
(3) Mixed results in static weight
Discounting CS3 (which had even rear weight
distribution to start), it appears that some
improvements were gained where the distribution
was not dramatically uneven to start with. In
execution I found this test method to be only
useful as a trend guide due to the reluctance of the
dogs to stand perfectly square and still during the
measurements. This was noted in the study by
Hyytiäinen (65) “healthy individuals15 have no
reason to focus on how they alter the weight
between their limbs, thus displaying lower
CS1 10:90 10:90
CS2 30:70 30:70
CS3 50:50 50:50
CS4 65:35 60:40
CS5 35:65 50:50
Table 7- Rear weight distribution before and after
Figure 10 – Demonstrating the percentage
improvements in hamstring extension
(4) No difference in stance duration, stride
duration, frequency and length
A common factor between all the case studies is
that these factors did not change after treatments.
We used the Bearded Collie from the Jena study
as a benchmark and found that 3 out of 5 (of the
case studies) had similar stride lengths, while 2
out of 5 had stride lengths noticeably lower.
(5) Qualitative assessments
Following the treatments we also surveyed the
owners to understand was there “any improvement
in athletic Agility performance”. 4 of the 5
owners answered positively, with the remainder
(CS1) deciding to retire the dog due to age and
arthritis rather than return to the competitive ring.
4 areas of limitation were identified which could
impact on the conclusion.
(1) The number of dogs and timeframe of
Drawing conclusions from 5 case study and
applying them as a generalisation is a recognised
limitation of case studies (71).
(2) Respective stages of tendinopathy
For each case study, the permission of the
respective veterinary surgeon was sort. In
particular, I highlighted the desire to treat tension
/ tightness in the hamstring tendon of origin. No
investigation was made, using diagnostic
equipment such as MRI and diagnostic ultrasound
(72) to verify the clinical assessment made by
palpation. This leads to 2 considerations:
(i) The problem may have been tendon
inflammation rather degenerative.
(ii) The stages of degeneration in each case study
may be different, thus impacting on treatment
(3) Equipment choice
Table 5 outlines the difference between long and
shortwave therapeutic ultrasound modalities. The
major difference is that longwave only produces
superficial heat. The research for treating
tendinopathy used in this paper, (29) (44) (43)
(55), all cited shortwave therapeutic ultrasound.
Heat is cited (72) to aid in the recovery from
chronic achilles tendinopathy. Therefore using
shortwave therapeutic ultrasound may have
improved or even added more consistency to the
(4) Choice of evaluation methods
To further improve my research findings I would
(i) A goniometer to compliment the hamstring
(ii) A dynamic GLS Lameness Test (Haas 2012)
instead of static weight analysis and the
stance, stride duration, frequency, length
However these 2 methods also have limitations
including reproducibility (45) and cost.
The study focused on the tendon(s) of origin for
the hamstring group as these are the prime
muscles for generating the dog’s forward motion
and jumping ability.
Competitive Agility dogs make extensive use of
this muscle and research showed that the
musculotendinous junction is the area where
hamstring injuries may occur, with tendinopathy a
Tendinopathy can be treated with therapeutic
ultrasound, deep-friction-massage and stretching.
These modalities were combined into a treatment
schedule to address reduction of scar tissue,
increasing blood flow / mechanical loading and
producing growth factors.
The treatment schedule did improve the natural
range-of-motion (measured as hamstring
extension) to varying degrees in all the Border
Collie’s used in these case studies. Although not
uniform, improvements were also noted in rear
weight distribution and reduction in the ‘lameness
score’. Additionally, if more subjectively, where
the dogs continued to compete in competitive
Agility classes the owners felt there had been a
4 out the 5 dogs in this study had experienced
other (different) injuries that the owner could
recall. This gives grounds for theorising that the
hamstring strains are compensatory in nature, but
this needs to be proven.
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