Purpose of the presentation

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1 Roles and functions of the hamstrings and quadriceps during lower body exercices Can-Fit-Pro 216 Presented by: Alexandre Paré, M.Sc., CSCS Kinesiologist Purpose of the presentation To eliminate confusion To train better To prevent injuries Hamstrings Semitendinosus, Semimembranosus, Biceps femoris Hamstrings Overall View Quadriceps Knee Lateral View Vastus Medialis Vastus Intermedius Vastus Lateralis Rectus Femoris

2 Knee Anterior cruciate ligament ACL Flexion Extension Anterior cruciate ligament ACL (role) ACL (role) Prevalence of ACL Injuries Sports demanding a simultaneous decelaration and rotation. Higher frequency in females. Sports: football, basketball, handball, soccer, alpine skiing, gymnastics 2 ACL injuries in the US, among which half are complete ruptures. Brukner, P., & Khan, K. (26). Clinical sports medicine. McGraw Hill. Escamilla, R. F. et al. (212). Journal of orthopaedic & sports physical therapy

3 Prevalence of injury ACL (injury mechanism) ACL (injury mechanism) Hamstring Injury Rates Hamstrings are the most often injured muscular group. 12 to 24 of all sport injuries Injuries can be caused by overtraining of the quads or a quadriceps/hamstrings ratio (Q/H) too pronounced. Ebben, W. P. (29). Hamstring activation during lower body resistance training exercises. Int J Sports Physiol Perform. Hamstring Injury Rates Hamstring Injury Rates The hamstring has an important role in the prevention of ACL injuries: Acts as ACL synergist Decreases anterior translation and medial rotation of the tibia. Acts as ACL stabiliser Overtraining the quadriceps can inhibit the hamstrings and decrease the articular stability of the knee. Luckily, stimulating the hamstrings during training will decrease their inhibition pattern. Ebben, W. P. (29). Hamstring activation during lower body resistance training exercises. Int J Sports Physiol Perform. Ebben, W. P. (29). Hamstring activation during lower body resistance training exercises. Int J Sports Physiol Perform.

4 Harput 214 Squat Front lunge Lateral lunge One-leg balance BW Escamilla 29 Wall squat One-leg squat 12 RM Escamilla 21 Squat Leg press 12 RM Contreras 216 Full front squat Full back squat Parallel back squat 1 RM McCurdy 21 Back squat Single leg squat 8 of 3RM Schoenfeld 2 Lying leg curl Stiff leg dead lift 8 RM Ebben 29 Back squat Deadlift Dynamic lunges Step-up Leg ext 6RM Gullett 29 Back squat Front squat 1RM Yavuz 2 Back squat Front squat 1RM Ebben 29 Back squat Seated leg curl Russian curl (nordic ham curl) Stiff leg dead lift Stiff leg dead lift, 1-leg Good morning 6RM Contreras 2 Hip thrust Back squat parallel 1RM Escamilla 22 Conventional deadlift Sumo deadlift 1RM Zebis selected therapeutic exercises 1. 1 leg forward jump 2. 1 leg side jump 3. One-leg jump on balance mat 4. One-leg landing from box jump on balance mat. One-leg landing from box on balance mat and jump again 6. Supine pelvis lifts 7. Supine one-leg curl 8. Nordic ham curl 9. Seated leg curl 1. Prone leg curl 11. Romanian deadlift 12. Hyperextensions off table 13. Hyperextensions off table with barbell 14. Two-hand kettlebell swings 3 rep / exercise Harput, G., Hayri-Ertan, R. S., Ergun, N., & Mattacola, C. G. (214). Effect of gender on the quadriceps-to-hamstrings coactivation ratio during different exercises. Journal of sport rehabilitation. 18 sujets, H-F 4 exercices sur wobble board: Fente avant Fente latérale Équilibre 1 jb Squat 1 jb 4 répétitions EMG en MVIC sur: Vaste latéral et vaste médial Biceps femoris et semitendineux RÉSULTATS Activation musculaire en du MVIC RÉSULTATS Activation musculaire en du MVIC Fente avant Femme Homme Fente latérale Femme Homme Harput., et al. (214) Femme Équilibre 1 jb 17 6 Homme Squat 1 jb Femme Homme Harput., et al. (214)

5 Fente avant: Q/I = 2, Femme Homme Équilibre 1 jb: Q/I =, Femme Homme Fente latérale: Q/I = 3, Femme Homme Squat 1 jb: Q/I = 2, Femme Homme Escamilla, R.(29). Cruciate ligament force during the wall squat and the one-leg squat. MSSE. 18 subjects, M-F 3 exercices: Wall squat short Wall squat long One-leg squat 12 RM EMG in MVIC on: Rectus femoris Vastus lateralis Vastus medialis Biceps femoris Semimembranosus Semitendinosus Quadriceps force during 3 exercices Hamstring force during 3 exercices Newtons Wall squat short Wall squat long One-leg squat Newtons Wall squat short Wall squat long One-leg squat Knee flexion ( ) Knee flexion ( ) Escamilla., et al. (29) Escamilla., et al. (29) Ratio Q/H 18, 16, 14, 12, 1, 8, 6, 4, 2,, Ratio Q/H during 3 exercices Wall squat short,8 Wall squat long 13, 13,1 One-leg squat 11,8 11,7 11,2 11,7 1,9 1,2 9,7 9,6 7,6 7,6,8,9 4,6 4, Knee flexion ( ) Escamilla., et al. (29) Escamilla, R. (21). Effects of technique variations on knee biomechanics during the squat and leg press. MSSE. 1 subjects, M 3 yo, 1 years experience 12 RM EMG in MVIC (EMG testing pretest not mentionned) on: Rectus femoris, Vastus lateralis, Vastus medialis Biceps femoris, Semimembranosus, Semitendinosus

6 Escamilla, R. (21). 2 exercices and 6 variations: Leg press High wide-narrow (129 kg) Leg press Low wide-narrow (129 kg) Squat wide-narrow (133 kg) Muscle activation MVIC Leg Press 12RM High-Narrow High-Wide Low-Narrow Low-wide No statistical difference between variations Rectus femoris Vastus lateralis Vastus medialis Biceps femoris Semi-T/M Escamilla., et al. (21) Muscle activation MVIC Narrow-parralel Squat 12RM Wide-3 Rectus femoris Vastus lateralis Vastus medialis Biceps femoris Semi-T/M 19 Escamilla., et al. (21) LP High- Wide Muscle activation MVIC No difference between exercises 9 LP Low-Wide Squat Wide-3 Quadriceps LP High- Narrow Hamstrings 12 LP Low- Narrow Squat narrow-parr Ebben, W. P., et al (21). Ebben, W. P., et al (29). Muscle activation during lower body resistance training. International journal of sports medicine. Muscle activation MVIC 2 subjects, M-F, exercices: Back squat, leg ext, deadlift, dynamic lunges, step-up 2 rep at 6RM RF EMG in MVIC on rectus femoris, vastus medialis, biceps femoris Squat Deadlift Step-up Dyn lunge Leg ext Ebben, W. P., et al (29).

7 Ratio in favor of quads Quadriceps / hamstring ratio / ratio 9 Q/I ratio 2,8 2,3 2,8 1,1 Squat Deadlift Step-up Dyn lunge Leg ext Ebben, W. P., et al (29). Gullett, J. C., et al. (29). A biomechanical comparison of back and front squats in healthy trained individuals. The Journal of Strength & Conditioning Research. sujets, H-F with strength training experience 2 exercices: Back squat (61kg) (1 RM = 88,3kg) Front squat (48 kg) (1 RM = 69,2kg) 7 1 RM (equivalent to 1RM) EMG in MVIC on rectus femoris, vastus lateralis, vastus medialis, biceps femoris, semitendinosus, lumbar extensors. Technique used Back squat parallel (12 knee flexion) Technique used Front squat parallel (12 knee flexion) Muscle activation MVIC Muscle activation MVIC RF VM ST Lext Back squat Front squat Back squat Front squat Gullett, J. C., et al. (29) Gullett, J. C., et al. (29)

8 Quadriceps / hamstring ratio / Ratio 4 3,8 3,6 3,4 3,2 3 2,8 2,6 2,4 2,2 2 3,3 Back squat 3,6 Front squat Q/H ratio Gullett, J. C., et al. (29) RÉSULTATS Forces applied to the knee Forces applied on the knee joint N / kg ,3* Back squat Front squat - -4,9 Compression Posterior shearing There are statistically more compression in the knee with the back squat = more risk of osteoarthritis and pain. The posterior shearing (usually expressed negatively): force necessary to stop the forward displacement of the tibia. 1. Compression force a) Increase the pressure on the posterior surface of the patella. b) Increase de tibiofemoral compression c) Increase meniscus compression 2. Shearing forces a) Anterior: would place the ACL under tension. b) Posterior: releases the tension on the ACL and is therefore protective. Gullett, J. C., et al. (29) 1- Knee compression forces on the patella 2- Shearing forces on the knee Kernozek.213. Critical Reviews in Biomedical Engineering The pressure on the posterior surface of the patella increases as the knee bend. The knee flexion angle reduces the patellar tendon angle thus reducing the line of pull of the tibia in the anterior shear direction The hamstring muscle is largely protective of the ACL, and its line of pull is greater for producing a posterior shear force as the knee is flexed.

9 Yavuz, H. U., et al. (2). Kinematic and EMG activities during front and back squat variations in maximum loads. Journal of sports sciences. Yavuz, H. U., et al. (2). Kinematic and EMG activities during front and back squat variations in maximum loads. Journal of sports sciences. 12 subjects, M 2 exercices: Back squat (19 kg) Front squat (8 kg) 1 1 RM EMG in MVIC on rectus femoris, vastus lateralis, vastus medialis, biceps femoris, semitendinosus, lumbar extensors, gluteus maximus. Yavuz, H. U., et al. (2) Muscle activation MVIC Muscle activation MVIC * RF VM ST LExt GM 1 Back squat Front squat Back squat Front squat Yavuz, H. U., et al. (2) Yavuz, H. U., et al. (2) Quadriceps / hamstring ratio Contreras, B., Vigotsky, A. D., Schoenfeld, B. J., Beardsley, C., & Cronin, J. B. (216). A Comparison of Gluteus Maximus, Biceps Femoris, and Vastus Lateralis Electromyography Amplitude in the Parallel, Full, and Front Squat Variations in Resistance-Trained Females. JAB. 2,4 2,2 2 1,8 1,6 1,4 1,2 1 Ratio / 2,1 1,8 Squat arr. Squat avant Ratio Q/I Yavuz, H. U., et al. (2) 13 subjects, F, 8 years of strength training 3 exercices: Full front squat (39 kg) Full back squat (47 kg) Parallel back squat (3 kg) 1 RM EMG in MVIC on: Gluteus maximus proximal Gluteus maximus distal Biceps femoris Vastus lateralis

10 RÉSULTATS Activation musculaire en du MVIC Segal, P. and Jacob, M., The Knee, Wolfe, London, p. 9, No significant difference GM proximal GM distal Full front squat Full back squat Parallel back squat 39 kg 47 kg 3 kg Contreras, B., (2) Escamilla, R. F. (21). Knee biomechanics of the dynamic squat exercise. Medicine and science in sports and exercise, 33(1), Results: Low to moderate posterior shear forces, restrained primarily by the posterior cruciate ligament (PCL), were generated throughout the squat for all knee flexion angles. Low anterior shear forces, restrained primarily by the anterior cruciate ligament (ACL), were generated between and 6 knee flexion. Patellofemoral compressive forces and tibiofemoral compressive and shear forces progressively increased as the knees flexed and decreased as the knees extended, reaching peak values near maximum knee flexion. Hence, training the squat in the functional range between and knee flexion may be appropriate for many knee rehabilitation patients, because knee forces were minimum in the functional range. Quadriceps, hamstrings, and gastrocnemius activity generally increased as knee flexion increased, which supports athletes with healthy knees performing the parallel squat (thighs parallel to ground at maximum knee flexion) between and 1 knee flexion. Furthermore, it was demonstrated that the parallel squat was not injurious to the healthy knee. Escamilla, R. F. (21). Knee biomechanics of the dynamic squat exercise. Medicine and science in sports and exercise, 33(1), Conclusions The squat was shown to be an effective exercise to employ during cruciate ligament or patellofemoral rehabilitation. For athletes with healthy knees, performing the parallel squat is recommended over the deep squat, because injury potential to the menisci and cruciate and collateral ligaments may increase with the deep squat. The squat does not compromise knee stability, and can enhance stability if performed correctly. Finally, the squat can be effective in developing hip, knee, and ankle musculature McCurdy, K., et al. (21). Comparison of lower extremity EMG between the 2-leg squat and modified single-leg squat in female athletes. J Sport Rehabil Muscle activation MVIC 11 subjects, F, athletes 2 exercices: Back squat and Single leg squat (both performe parallel) 8 of 3RM EMG in MVIC on: Gluteus medius Biceps femoris Rectus femoris Back squat 71* 7* 4* Single leg squat RF Gmed *Denotes a statistically significant difference from the back squat. McCurdy, K., et al. (21)

11 Schoenfeld, B. J et al. (2). Regional differences in muscle activation during hamstrings exercise. The Journal of Strength & Conditioning Research. Semitendinosus Biceps femoris 1 subjects, M 2 exercices: Lying leg curl Stiff leg dead lift 8 RM EMG in MVIC on proximal and distal semitendinosus, proximal and distal biceps femoris. Ref: Semitendinosus Biceps femoris Muscle activation MVIC Muscle activation MVIC ST prox ST dist prox dist 2 2 Stiff leg DL Lying Leg curl Stiff leg DL Lying leg curl Schoenfeld, B. J et al. (2) Schoenfeld, B. J et al. (2) Muscle activation MVIC Average results by grouping the semitendinosus and the biceps femoris Muscle activation MVIC * 9 19* STP STD P D ST total total 2 2 Stiffed leg dead lift Lying leg curl Stiffed leg dead lift Lying leg curl Schoenfeld, B. J et al. (2) Schoenfeld, B. J et al. (2)

12 Ebben, W. P. (29). Hamstring activation during lower body resistance training exercises. Int J Sports Physiol Perform 34 subjects, M-F, athletes 6 exercices: Back squat Seated leg curl Russian curl (nordic ham curl) Stiff leg dead lift Stiff leg dead lift, 1 leg Good morning 6 RM EMG in MVIC on rectus femoris and biceps femoris. Russian curl (nordic ham curl) Stiff leg dead lift Stiff leg dead lift, 1 leg Good morning Muscle activation MVIC Contreras, B., (2). A Comparison of Gluteus Maximus, Biceps Femoris, and Vastus Lateralis EMG Activity in the Back Squat and Barbell Hip Thrust Exercises. Journal of applied biomechanics. Ahead of print Russian curl 81 7 Seated leg curl Stiff leg dead lift 2 One leg Stiff leg dead lift GM Back squat Biceps femoris Rectus femoris 13 subjects, F 6 exercices: Hip thrust and back squat parallel 1 RM EMG in MVIC on: Gluteus maximus proximal Gluteus maximus distal Biceps femoris Vastus lateralis Ebben, W. P., et al (29) Muscle activation MVIC * 69* 41* 4 GM proximal 29 GM distal Hip thrust Back squat *Denotes a statistically significant difference from the back squat. Contreras, B., (2) Escamilla, R. F.(22). An electromyographic analysis of sumo and conventional style deadlifts. MSSE. 12 subjects, M 2 exercices: Conventional deadlift Sumo deadlift 12 RM (123kg (27 lbs)) EMG in MVIC on: Rectus femoris, vastus lateralis, vastus medialis Biceps femoris, semimembranosus, semitendinosus Hip adductors Gluteux maximus Rectus abdominis, external obliques

13 Muscle activation MVIC Muscle activation MVIC Quad Hamstring HA GM RA-EO * 44* 4* 36* RF VM ST/M HA GM RA OE Conventional deadlift Sumo deadlift Conventional deadlift Sumo deadlift Escamilla., et al. (22) Escamilla., et al. (22) Zebis MK et al. (212). Kettlebell swing targets semitendinosus and supine leg curl targets biceps femoris: an EMG study with rehabilitation implications. Br J Sports Med. Purpose of the study: During dynamic movements, coactivation of the hamstrings is important prevent excessive ACL shear forces. Objective The aim was to investigate the medial and lateral hamstring muscle activation balance during 14 selected therapeutic exercises. 14 exercises for hamstring One-leg forward jump (FJ) Subjects: 16 female elite handball and soccer players. 23 years old, no knee injury. Regular strength training for,4 years. Protocol: EMG activity of the biceps femoris () and semitendinosus (ST) was measured during strengthening and balance/coordination exercises, and normalised to EMG during maximal voluntary isometric contraction (MVIC). 3 reps/exercise. One-leg side jump (SJ) One-leg jump onto balance mat maintain 3 sec (FJU) One-leg landing from box on balance mat, maintain 3 sec (LU) One-leg landing from box on balance mat and jump again (DJU) Supine pelvis lifts (SPL) Supine one-leg curls (SuLC) Nordic ham curl (NH)

14 Seated leg curl, best trial at 6 / sec (SeLC) Hyperextensions off table (HE) Prone leg curl, best trial at 6 / sec (PrLC) Hyperextensions off table with barbell 3 pounds (HEB) Romanian deadlift (weight for 12RM) (RD) Two-hand kettlebell swings 12kg or 16kg (KS) Muscle activation MVIC Jumps exercices FJ SJ DJU FJU LU Semitendinosus Biceps femoris 2 18 Zebis et al (212). Back extension 6 Body weight Machine SPL SuLC NH PLC SeLC RD HE HEB KS Muscle activation MVIC Semitendinosus Biceps femoris Zebis et al (212). THE IMPORTANCE OF WORKING YOURS HAMSTRING. TO COUNTER THE ACTION OF THE QUADRICEPS apare@alexandrepare.com