John Orchard, MBBS BA MD PhD FACSP FACSM FASMF FFSEM (UK) Prof, School of Public Health, University of Sydney PRP for Quadriceps Muscles Injuries 8th MuscleTech Network Workshop 3rd October, Barcelona

1. Mechanism of Rectus Femoris
Injuries
John Orchard, MBBS
BA MD PhD FACSP FACSM
FASMF FFSEM (UK)
Prof, School of Public Health,
University of Sydney
October 3, 2016
8th MuscleTech Network
Workshop, Barcelona
Delivered remotely
1

2. When do muscles strain?
n Very little is proven about the time of
occurrence of strains
n Strains can be recreated in the laboratory,
but in vivo occur so rapidly that the forces
resulting in strain are very hard to assess
n Quadriceps strains in theory could occur in
swing phase, ground contact phase and ball
contact phase (kicking)
n In punt kicking, no ground reaction force
involved in ball contact
2

3. Clinical occurrence of strains
Hamstring Football,
sprints
Full pace ?swing ?
stance
Quadriceps Soccer,
ARF
Kicking ?ball/swing/
ground
Calf Tennis,
squash
Take-off Ground
contact
Groin Soccer,
ARF
Change
direction
Ground
contact
Upper limb clinically
rare
tackling Player
contact 3

4. When do muscles strain?
n In real life activities, highest range of
motion (stretch) generally occurs during
swing phases (least external force)
n Highest external joint moments generally
occur during ground phases in mid range
n Does low(er) force in a high(er) risk phase
cause the injury or high(er) force in a lower
risk phase cause the injury?
4

5. Forces on muscles and joints
n Change of movement of a joint is
determined by a sum of net muscle moment
and net external moment
n Leiber et al. (1993, JAP) showed that in the
laboratory strain model, muscle strain
damage correlated with external force
applied rather than over activity of the
muscle.
n Maximal net muscle moments probably
coincide with maximal external moments in
the other direction 5

6. Biomechanics: calf strains
n Occur during ground contact phase
n Occur during close to full range (increased
stretch) but not maximal range
n Close to an isometric phase (moving from
eccentric to concentric)
n Occur during push-off (acceleration) of
second step
6

7. Before and after frames
7

8. Quad strains - dominant kicking
leg in football codes
n Quadriceps strains
much more common
in dominant kicking
leg (RR 2.13, 95% CI
1.59-28.6 in AFL);
same pattern in soccer
n Hamstring and calf
fairly evenly
distributed
8

9. Quadriceps strains?
n Anecdotal description of occurrence during
ball contact
n But, this would clearly be when shortening
n Why wouldn’t triceps strain when serving
or spiking in volleyball if ball contact can
strain a shortening muscle?
n Could quadriceps strain occur in back-
swing or even ground contact?
9

10. Possible phases: rugby kick
10
GRF
BRF
stretch

11. Possible phases: AFL kick
11
GRF
BRF
stretch

12. Video of AFL kicking/strains
n Play video here
12

13. Type of kicks at risk for QdStr
n Running kicks rather than standing kicks
n Rare on kicking out from goal, or kicking
after a mark (Aust football) or goalkeepers
(soccer)
n Very rare in punters in NFL
n Rare in goalkickers in rugby codes
n Related to speed of running rather than
distance of kick
13

14. Quadriceps strains can occur
running
14
GRF

15. In kicking usually short kicks
15
GRF

16. AFL quads injury risks
Injury Variable B S.E Risk
ratio
95%
CI
Quadriceps injury
risks
Orchard, J., Intrinsic
and extrinsic risk
factors for muscle
strains in Australian
footballers. Am J
Sports Med, 2001: p.
300-303.
Quadriceps injury within
previous 8 weeks
2.75 0.21 15.61 10.27-2
3.74
Previous quadriceps injury
(more than 8 weeks ago)
1.30 0.18 3.67 2.60-5.
19
Hamstring injury within
previous 8 weeks
0.73 0.32 2.08 1.12-3.
86
Low rainfall at match venue in
previous 7 days
0.37 0.18 1.45 1.01-2.
08
Shorter player (<=182 cm) 0.39 0.16 1.48 1.09-2.
02
16

17. Ball pressure no relation
Quad strain during
game?
Matches
Average ball pressure (Psi)
1st quarter 2nd quarter 3rd quarter 4th quarter Spare balls
Start End Start End Start End Start End 1 2
Yes 8 10.88 10.50 10.88 10.79 10.94 10.79 10.94 10.79 12.56 12.50
No 72 10.99 10.61 11.00 10.74 10.99 10.79 11.00 10.95 12.29 12.43
17

18. No relation ground hardness
Penetrometer reading
Harder
(2.5 or less)
Medium
(2.6 - 3.0)
Softer
(3.1 or
greater)
Matches with this reading 184 243 226
Quadriceps strains occurring 9 18 9
Quadriceps strains match
incidence (injuries per 1000
player hours)
0.8 1.3 0.7
18

19. BRF relates to distance kicked
19
Running
speed
Kicking
distance
Ball condition
9psi 12psi Wet
fast 20m 1160 1292 1689
130 255 168 SD
fast 40m 1582 1703 2186
776 187 352 SD
medium 40m 1592 1687 2146
215 153 244 SD

20. Biomechanics: quadriceps strains
n Can occur when running (slowing down)
not just kicking
n Related to dry weather rather than wet
weather (?ground contact)
n Mechanism: perhaps caused by under-
striding of kicking leg during final step
(when slowing down) before the kicking
motion
20

21. Can force in a tendon be directly
measured?
n Answer – Yes; but it has only been done to
date by one research group and for Achilles
(calf) and patella (quadriceps) tendons in
taking off and landing.
n Finni T. et al. “In Vivo…” Eur J Appl
Physiol (2000). 83: 416-26 and Eur J Appl
Physiol (2001). 85: 170-76
n Forces in tendons in swing phases
negligible compared to ground contact 21

22. Forces in PT/AT (arrow = stance/swing
phase change)
Take-off Landing
22

23. BRF not related to quad strains
n Ground reaction forces in kicking are greater than ball reaction forces.
n Speed of running during a kick (which relates to ground reaction forces) is a greater risk
for quadriceps injury than distance kicked (which relates to ball reaction forces) in
Australian football.
n In other sports, the relative risks follow the same patterns (e.g. running passes in soccer
= higher risk, punting from a standing start in the NFL = low risk, goal kicking in rugby
= low risk).
n Deceleration during running (without ball involvement) can cause a rectus femoris
strain.
n The action of the kicking leg in a running kick (during the final step and back-swing) is
similar to a deceleration movement in running, and hence the timing of injury is
probably the same in both.
n Ball impact forces are greater on wet days when the risk of quadriceps strain is not
higher.
n Ball pressure does not correlate with risk of quadriceps strain.
n Basic science studies suggest that stretch (muscle length) is an important determinant of
muscle failure during a strain injury. The rectus femoris is not stretched during ball
contact.
n Upper limb muscles during swing phases that are retarded by a ball in a similar manner
to rectus femoris (e.g. the triceps during volleyball serving) do not commonly strain. 23

24. Conclusion
n Lower limb muscles prob. strain during
stance phase, when external joint moments
(& muscle reactive moments) are high
n These instances probably are in situations of
relative overstretch (but not maximum)
n In gait cycle quadriceps probably
deceleration when slowing down to kick
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