Intrinsic Foot Muscle Activation During Specific Exercises: A T2 Time Magnetic Resonance Imaging Study.
BACKGROUND
The intrinsic foot muscles maintain the medial longitudinal arch and aid in force distribution and postural control during gait. Impaired intrinsic foot-muscle function has been linked to various foot conditions. Several rehabilitative exercises have been proposed to improve it; however, literature that identifies which individual muscles are activated during specific intrinsic foot-muscle exercises is lacking.


OBJECTIVE
To describe changes in activation of the intrinsic plantar foot muscles after 4 exercises as measured with T2 magnetic resonance imaging (MRI).


METHODS
Descriptive laboratory study.


METHODS
Research laboratory.


METHODS
Eight healthy National Collegiate Athletic Association Division I collegiate cross-country and track athletes (5 men and 3 women: age = 20 ± 0.93 years, height = 180.98 ± 10.84 cm, mass = 70.91 ± 7.82 kg).


METHODS
Participants underwent T2 MRI before and after each exercise. They completed 1 set of 40 repetitions of each exercise (short-foot exercise, toes spread out, first-toe extension, second- to fifth-toes extension).


METHODS
Percentage increases in muscle activation of the abductor hallucis, flexor digitorum brevis, abductor digiti minimi, quadratus plantae, flexor digiti minimi, adductor hallucis oblique, flexor hallucis brevis, and interossei and lumbricals (analyzed together) after each exercise were assessed using T2 MRI.


RESULTS
All muscles showed increased activation after all exercises. The mean percentage increase in activation ranged from 16.7% to 34.9% for the short-foot exercise, 17.3% to 35.2% for toes spread out, 13.1% to 18.1% for first-toe extension, and 8.9% to 22.5% for second- to fifth-toes extension. All increases in activation had associated 95% confidence intervals that did not cross zero.


CONCLUSIONS
Each of the 4 exercises was associated with increased activation in all of the plantar intrinsic foot muscles evaluated. These results may have clinical implications for the prescription of specific exercises to target individual intrinsic foot muscles.
University of Virginia, Charlottesville.
Thomas M
TM
Gooding
University of Virginia, Charlottesville.
Mark A
MA
Feger
University of Virginia, Charlottesville.
Joseph M
JM
Hart
University of Virginia, Charlottesville.
Jay
J
Hertel
D018592:Cross-Over Studies; D015444:Exercise / Q000502:physiology*; D005260:Female; D005528:Foot / Q000502:physiology*; D005684:Gait / Q000502:physiology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D055815:Young Adult
medial longitudinal arch; muscle functional magnetic resonance imaging; short-foot exercise; toes spread out
Magn Reson Med. 2007 Aug;58(2):335-45
17654591
Phys Ther Sport. 2011 Feb;12(1):30-5
21256447
Clin Biomech (Bristol, Avon). 2012 Jan;27(1):46-51
21864955
J Magn Reson Imaging. 2012 Jun;35(6):1253-65
22588992
J R Soc Interface. 2014 Jan 29;11(93):20131188
24478287
Clin Biomech (Bristol, Avon). 2012 Jun;27(5):500-5
22166747
J Back Musculoskelet Rehabil. 2013;26(2):163-8
23640317
Foot Ankle Int. 2005 Dec;26(12):1081-8
16390643
J Phys Ther Sci. 2014 Apr;26(4):619-20
24764646
J Orthop Sports Phys Ther. 1987;9(1):11-6
18794588
Clin Sports Med. 2015 Apr;34(2):347-61
25818718
Foot Ankle Int. 2002 Jul;23(7):629-33
12146774
Br J Sports Med. 2015 Mar;49(5):290
24659509
Invest Radiol. 2009 Nov;44(11):741-7
19809343
J Foot Ankle Res. 2012 Nov 26;5(1):29
23181771
J Electromyogr Kinesiol. 2008 Jun;18(3):420-5
17208458
Magn Reson Imaging. 2003 Oct;21(8):853-61
14599535
BMC Musculoskelet Disord. 2013 Jan 28;14 :45
23356426
J Back Musculoskelet Rehabil. 2011;24(4):225-31
22142711
J Bone Joint Surg Am. 1964 Apr;46:469-81
14131426
J Electromyogr Kinesiol. 1994;4(3):131-42
20870553
Man Ther. 2013 Oct;18(5):425-30
23632367
J Foot Ankle Surg. 2003 Nov-Dec;42(6):327-33
14688773