cj cummings

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Anthropometrics and Bar Kinematics of the Snatch Technique in an Elite Youth Weightlifter: C.J. Cummings Bob LeFavi, PhD, CSCS, USAW Armstrong State University (Savannah, GA) Team Savannah

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Page 1: Cj cummings

Anthropometrics and Bar Kinematics of the Snatch Technique in an

Elite Youth Weightlifter:C.J. Cummings

Bob LeFavi, PhD, CSCS, USAWArmstrong State University (Savannah, GA)

Team Savannah

Page 2: Cj cummings

C.J. Cummings

Page 3: Cj cummings

Weightlifting Accomplishments• At 11 years old, double bodyweight clean and jerk; first in history.• In December 2012, C.J. was the youngest lifter ever to compete in (qualify for)

the American Open in Palm Springs, CA. He placed second as a 12 year-old!• From 2013 to present, C.J. has been the #1 ranked 17 & under male lifter in U.S.• In April 2013, as a 12 year-old, C.J. was the youngest competitor in history to

represent the U.S. at an international weightlifting championship.• In 2013, C.J. lifted for Team USA at the International Weightlifting Federation’s

15 & Under Pan American Championships, where he won, was awarded the best overall lifter, and set new Pan American records. This was the first time in over a decade that a U.S. male has broken an International record.

• After the Pan Americans, USA Weightlifting designated C.J. the strongest 13 & Under lifter in the Western Hemisphere. USAW later designated him as the strongest 13 & Under lifter in the world!

• In 2014, at 13, C.J. won the 62 KG class at 17 & Under Pan American Championships in May in Peru.

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Purpose

• Identify anthropometric and performance variables of this elite Youth weightlifter.

• Compare data against current recommendations and thought.

• Initiate a database of anthropometric and performance variables so that weightlifting talent may be mot easily identified in the future.

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Literature on Athropometrics

• Anthropometrics– Identified certain variables as advantageous to

weightlifting, yet scant amount of actual research– National Coach Zygmunt Smalcerz (previously

identified talent in Poland) has published anthropometric preferences.

– Studies on powerlifters show similarities (longer arms than normal) and differences (shorter torso relative to leg length in powerlifters; shorter leg length relative to torso in weightlifters) in optimal anthropometrics.

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Anthropometric Measurements

• Bodyweight and height• Body Segments:– Total arm length (acromion process to dactylion)– Torso length (acromion process to greater trochanter)– Femur length (greater trochanter to lateral femoral

condyle)– Tibia length (lateral femoral condyle to lateral

malleolus)– Forearm length (olecranon process to styloid process)– Hand length (interstylon midpoint to dactylion)

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Literature on Barbell Kinematics

• Barbell kinematics– Early work done by Dr. John Garhammer and Dr.

Michael Stone. Identification of technique variables in world-class weightlifters. Looked at:• Optimal bar displacement (total distance bar travels).• Vertical velocity pattern throughout lift (speed of bar

upward; max velocity reached towards end of 2nd pull).• Barbell trajectory patterns (path of bar relative to

vertical reference line, focused on minimizing distance away from that line)

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Does Optimal Technique Exist?

• Or if the question is, “What is optimal for a certain individual?”, then what data do we have to assist coaches in identifying a lifter’s optimal technique?

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Barbell Kinematics

• 3D motion analysis• 10 cameras• Two marker sets of three reflective markers• Trials of single repetitions were completed at

40 kg, 50 kg, 60 kg, 70 kg, 80 kg, and 90 kg• The trials ranged from 35% - 80% of the

subjects one repetition maximum

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RESULTS: Anthropometrics

Height – 160 cm Weight – 64 kg

Absolute Variables (cm)

Left Right

Total Arm 54 53.5

Forearm 27 27

Hand 18.5 18.5

Torso 47.5 48

Femur 34.5 35

Tibia 45 44.5

• Smalcerz’s Suggestions:– Long arms compared to torso

• Easy to lift bar off platform• Harder to raise bar higher in

jerk – Shorter femur length

compared to tibia– Legs should not be more than

50 percent of total height– Hand length should be at

least 16-16.5 cm

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RESULTS: Barbell Displacement

• As the weight increases, the lifter is not able to pull the bar as high

• Peak displacement in successful lifts has been shown to be lifted up to 70 percent of the lifters height

• The bar was lifted as low as 59 percent of the lifters height for the heaviest lift

(m) 40 kg 50 kg 60 kg 70 kg 80 kg 90 kg

2nd pull 1.15 1.15 1.09 1.06 1.05 0.95

Recovery 1.55 1.49 1.40 1.37 1.53 1.38

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RESULTS:Barbell Velocity

• Velocity should be continuous throughout the lift, although a dip in velocity between the 1st pull and 2nd pull is common.

• Maximum velocity expected to be seen during the 2nd pull phase.

• Most research done on heavy, competitive lifts which reach a range of 1.68 to 1.98 m/s

-1

0

1

2

3

1.7 1.9 2.1 2.3 2.5 2.7 2.9

Verti

cal V

eloc

ity (m

/s)

Time (s)

40 kg

-1

0

1

2

3

1.7 1.9 2.1 2.3 2.5 2.7 2.9

Verti

cal V

eloc

ity (m

/s)

Time (s)

50 kg

-1

0

1

2

3

1.7 1.9 2.1 2.3 2.5 2.7 2.9

Verti

cal V

eloc

ity (m

/s)

Time (s)

60 kg

-1

0

1

2

3

1.7 1.9 2.1 2.3 2.5 2.7 2.9

Verti

cal V

eloc

ity (m

/s)

Time (s)

70 kg

-1

0

1

2

3

1.7 1.9 2.1 2.3 2.5 2.7 2.9

Verti

cal V

eloc

ity (m

/s)

Time (s)

80 kg

-1.0

0.0

1.0

2.0

3.0

1.6 1.8 2 2.2 2.4 2.6 2.8 3

Verti

cal V

eloc

ity (m

/s)

Time (s)

90 kg

Vmax (m/s)

40 kg 50 kg 60 kg 70 kg 80 kg 90 kg

2nd pull 2.71 2.76 2.68 2.31 2.20 2.19

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RESULTS:Barbell Trajectory• Lighter lifts, bar extends

further away from body than usual

• Heavier lifts keep close to vertical reference line

• Second pull has unique hitch

• Backward jump creates increase in backward horizontal displacement

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90 KG snatch

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Bar Trajectory ClassificationsMore type B? More type C? Three basic types of bar trajectories that

are widely used in research

Figure from Vorobyev, A.N. A Textbook on Weightlifting, 1978

Similar to 60 kg liftSimilar to 70 kg lift

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Conclusion

• The results from this study are specific to this one individual, and other lifters should not necessarily adopt these patterns.

• C.J. Cummings has anthropometric and technique characteristics that are somewhat unique.

• This data can be used to continue a database of variables on characteristics of elite lifters in the hope that such findings can assist coaches in the identification of weightlifting talent or to optimize a lifter’s potential.