Introduction

Methods

Results

References

Diana N. Webber, Geoffrey Handsfield, Niccolo Fiorentino, Silvia S. Blemker Department of Mechanical and Aerospace Engineering University of

Virginia, Charlottesville, Virginia

Diana N. Webber, Geoffrey Handsfield, Niccolo Fiorentino, Silvia S. Blemker Department of Mechanical and Aerospace Engineering University of

Virginia, Charlottesville, Virginia

The most frequently injured muscle within the hamstrings group is the biceps femoris long head (BFlh) [2]. Research suggests that the relative width of the proximal aponeurosis affects the distribution of strain across the muscle, which could account for the frequency of injury to this region [1].

In this study, magnetic resonance (MR) images were used to measure hamstring muscles and tendons to determine the variability of aponeurosis morphology in a population.

The teaching module inspired by this study was designed for high school Biology students and addresses the Virginia Standards of Learning (SOLs). Students will gain an appreciation of the nano-scale, as related to muscle contraction, and will practice with the scientific method, particularly hypothesis formation, experimenting, graphing, and reporting results and conclusions. More importantly, students will gain exposure to current scientific research to motivate them to pursue careers in science and engineering.

Variability in Muscle-Tendon Morphology

MR images of the thigh were obtained from fourteen volunteers (eight male and six female, height range: 157.5-195.6 cm, weight range: 54.4-102.1 kg, age range: 21-39 years) according to a previously described technique [3].

Fig. 2. Axial MR image. The BFlh (blue), ST (yellow), SM (green), and BF short head (pink) have been segmented.

• BFlh volume and PCSA show high correlation with total hamstring muscle volume and CSA.

• A range of tendon and aponeurosis morphologies existed among the subjects, and results showed little correlation between BFlh PCSA and proximal

aponeurosis width.• Hamstring strain and injury susceptibility may be highly variable across a

population.

1. Rehorn, MR, Blemker, SS. The effects of aponeurosis geometry on strain injury susceptibility explored with a 3D muscle model. Journal of Biomechanics (2010), doi: 10.1016/j.jbiomech.2010.05.011.

2. Armfield, D.R., Kim, D.H., Towers, J.D., Bradley, J.P., Robertson, D.D., 2006. Sports-related injury in the lower extremity. Clinics in Sports Medicine 4, 803-842.

3. Handsfield, G, Fiorentino, N, Blemker, SS. Variability in biceps femoris long head muscle-tendon morphology. Submitted to ASB, 2010.

4. Anderson JL., Schjerling P, Saltin B. Muscles, Genes, and Athletic Performance. Scientific American, Sept. 2000.

5. Romanian deadlift. http://www.womenshealthmag.com, Jan. 2010.

Pedagogy Adaptation Methods

Virginia SOLs addressed

Discussion

Abstract

BIO .1 (a, b, c, d, e, f, g, h, i, j, k, l, m)BIO .2 (b)BIO .3 (a, c, e)BIO .4 (d)

Acknowledgements

I would like to express my sincere gratitude to Dr. Silvia Blemker, Geoffrey Handsfield, Niccolo Fiorentino, and the rest of the M3 Lab for their assistance and support throughout this project. I would also like to thank Ms. Carolyn Vallas and Ms. Juliet Trail from the Center for Diversity in Engineering. Most of all, I would like to thank the NSF for providing the grant to support this project.

Fig. 3. 3-D reconstruction of the hamstring muscle group.

Injuries to hamstrings muscles are common and can be devastating to athletes. The structure of the aponeurosis, which is the section of flat tendon adjacent to the muscle, has been linked to injury susceptibility [1]. In this study, magnetic resonance imaging (MRI) was used to determine if aponeurosis width varies significantly in a population. Results show aponeurosis morphology is variable, and some people may be at higher risk for injury. A module, inspired by the research, was designed to foster critical thinking and inquiry-based learning among high school students. Students will identify and apply principles of scientific investigation to current biological research.

Learning Activities

Day 1: Background Information• Introduce muscle hierarchy (Figure 6) and mechanism of muscle contraction on the nano-scale. • Demonstrate the importance of small muscle cell size by allowing students to act out muscle contraction in both large and small scale on a football field (Figure 7).• As a result, students will understand the importance of surface area to volume ratio at the cellular level.

Day 2: Data Collection•Review steps of the scientific method.•Introduce muscle-tendon morphology research and apply it to scientific investigation.•Students will measure the area of the BFlh and the width of the aponeurosis on a MRI (Figure 2).•Students will measure the circumference of their thigh and calculate their body mass index (BMI). •Students will complete a series of Romanian Dead Lifts to exercise their hamstrings muscles (Figure 8).

The semimembranosus (SM), semitendinosus (ST), and biceps femoris (BF) muscles were segmented (Figure 2), along with the BFlh’s proximal tendon and aponeurosis. Lengths and volumes of the muscles and tendons were found using Materialise Mimics 13.1 3-D reconstruction feature (Figure 3).

Figure 6. Hierarchical structure of skeletal muscle.Source: Adapted from Scientific American, Sept. 2000, [4].

Fig. 5. Correlations between BFlh CSA and BMI (a, n=12) and BFlh CSA and height (b, n=13).

Fig. 4. Morphological correlations between BFlh and hamstring (a. and b.) and between BFlh and tendons (c. and d., n=18)Source of graphs c and d: Handsfield et. al., 2010, [3])

Fig. 1. MRI-based BFlh model.Adapted from Rehorn, et al. 2010 [1].

BFlh

Proximal aponeurosis

Proximal external tendon

Figure 7. Student activity: Muscle contraction.

Day 3: Results and Conclusions• Students will compile their data to create a graph similar to Graph D (Figure 4).• Student will quantify soreness they experience from the Romanian Dead Lift.• Students will use graphs (Figure 5) to estimate their Hamstring CSA.• Student performance will be assessed based on accuracy of data collection and graphs.

Fig. 8. Correct Romanian Dead Lift form. Source: www.womenshealthmag.com, 2010 [5].

c.

Hamstring CSA vs. BMI

R2 = 0.736152025303540

19 24 29

BMI (kg/m2)

Ham

stri

ng

CS

A

(cm

2)

b.

0

10

20

30

40

50

40

30

20

10

0

End Zone

X X X X X X X X X

Ca+ Ca+

X X X X X X X X X

End Zone

0

10

20

30

40

50

40

30

20

10

0

BFlh PCSA vs. Hamstring CSA

R2 = 0.7049

10

15

20

25

30

35

40

15 20 25 30 35 40

Hamstring CSA (cm2)

BF

lh P

CS

A (

cm

2 )

b.

Mean Prox. Aponeurosis Width

vs. BFlh PCSA

R2 = 0.01964

9

14

0 10 20 30 40

BFlh PCSA (cm2)

Av

era

ge

A

po

ne

uro

sis

W

idth

(m

m)

BFlh Volume vs. Hamstring Volume

R2 = 0.8161

100

150

200

250

300

350

380 580 780 980

Hamstring Volume (cm3)

BF

lh V

olu

me

(cm

3)

a.

d.

Hamstring CSA vs. Thigh Circumference

R2 = 0.4687

15

20

25

30

35

40

50 55 60 65

Thigh Circumference (cm)

Ham

stri

ng

CS

A

(cm

2)

a.