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Hamstring  Study

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Title: Hamstring Strength Testing vs. Knee Flexion Strength Testing 

 

Author: Carl Gustafson PT ATC LAT CSCS, Danielle Gorman DPT, Dawn Miller PTA

 

Affiliation: ATI Physical Therapy,  Medfield Ma. 02052

 

Article

 

Hamstring strength measures are described in the literature as an important measurement to determine readiness to return to sport after an ACL injury and subsequent surgery.  Comparisons of the strength of hamstrings from the affected to non-affected side, as well as comparisons as a ratio of strength to the antagonist quadricep are typical information gathered. (1) However, little adherence when testing accounts that the gastrocnemius greatly assists the hamstring in knee flexion when the foot is dorsiflexed. 

 

The literature clearly shows that the gastrocnemius assists the hamstring, however, there is little to no data to measure how much. (2) Although any Physical therapist, Athletic Trainer, or Exercise Physiologist would tell you that the gastrocnemius assists the hamstring with knee flexion, most of these disciplines don’t account for the gastrocnemius assistance when rehabbing or testing. In talking with 5 large Hospital / Private practice PT clinics none of them take into account gastrocnemius muscle involvement during rehab or when testing knee flexion strength but refer to it as hamstring testing.

 

When a health care provider refers to measuring hamstring strength the foot should be plantar flexed to minimize gastrocnemius involvement. When the foot is plantar flexed the gastrocnemius has much less ability to assist in knee flexion. ( Active insufficiency) (3). This should be called a Hamstring Strength Test.

 

However, a component of testing can also be with the foot dorsiflexed which would maximize overall knee flexion strength. This is important when testing overall knee flexion strength when compared to extension strength. ( referred to as quad/ ham ratio).

However, the term should not be referred to as quad /ham ratio but as knee extension strength vs. knee flexion strength ratio. 

 

We thought it would be interesting and informative to devise a test to differentiate hamstring strength from knee flexion strength. 

 

This would shed light on an estimate of the involvement of the gastrocnemius when doing a  knee flexion strength program. It would allow rehab specialists to gain knowledge of how to train the hamstring to restore individual muscle function post-operatively compared to the non-affected hamstring.

 

Method 

We gathered 20 healthy clients who frequented the local health club where our private practice physical therapy clinic is located. On the questionnaire, we gathered information from those clients who reported no current or past knee or ankle injuries.

 

To determine the extent of gastrocnemius assistance during knee flexion we performed a 2-legged,1 set of hamstring curls to muscular failure with feet plantar flexed. Once the patient could not complete another full repetition the patient was then instructed to dorsi flex their ankles and continue to do as many more complete repetitions until they couldn’t complete another full repetition.

 

Results

 

 

Subject Name

Sex

Age

Body Weight

Hamstring Weight

Reps PF

Reps DF

Total Reps

%

1

F

27

115

45

16

10

26

38% >

2

F

42

145

45

15

15

30

50%>

3

M

57

165

100

10

6

16

38% >

4

F

33

170

45

20

15

35

42%>

5

F

38

172

55

15

20

35

57%>

6

M

24

160

85

20

8

28

28%>

7

F

21

156

45

20

25

45

55%>

8

M

18

155

45

15

5

20

25%>

9

F

26

160

55

11

11

22

50%>

10

M

19

150

55

38

15

53

28%>

11

M

47

165

70

20

10

30

33%>

12

M

16

195

100

15

5

20

25%>

13

F

26

145

70

16

11

27

40%>

14

F

57

125

45

25

6

31

20%>

15

F

54

145

45

25

16

41

39%>

16

M

18

210

70

20

15

35

42%>

17

M

26

145

55

30

10

40

25%>

18

F

11

110

40

18

5

23

21%>

19

F

19

115

55

26

13

39

33%>

20

F

25

125

70

15

5

20

25%>

Totals

8M/12F

30.2

145.45

59.75

19.5

11.3

30.8

36.6%>

 

 

 

 

Of the 20 subjects, 12 were female, and 8 were male. The average age was 30 years old. The average body weight was 145 lbs. The average weight that patients failed was 59.75 lbs. The hamstring machine was in 15 lb. increments. The average number of repetitions the patients failed at with their feet plantar flexed was 19.5. The average amount of reps that a subject could do further with feet dorsi flexed was 11.3. The total reps to compete for failure was 30.8. The results demonstrated that the patients had statistically done 37% greater repetitions with their feet dorsiflexed compared to plantar flexed. 

 

 

Discussion

 

This test minimizes gastrocnemius involvement in the first part of the test when the feet are plantar flexed (active insufficiency) and maximizes gastrocnemius involvement in the latter part of the test when the feet are dorsiflexed. However, we don’t know if it completely negates gastric involvement in the beginning. We couldn’t find any articles to truly give the  % of gastrocnemius involvement when the ankle is dorsiflexed.

 

The literature shows that the quadricep is approximately 33% stronger than the hamstring( same side) in a healthy athlete. (4)  This ratio doesn’t take into account the gastrocnemius is assisting. 

There is some debate if the gastrocnemius when the athlete is running is only used as an ankle plantar flexor (creating an antagonist motion on the ACL/anterior draw) or if it helps to flex and protect the knee with the hamstring when the knee is going into valgus or hyperextension? (5). Could the gastrocnemius be an antagonist during the gait cycle of running but as soon as the hamstring senses a hyperextension or valgus moment at the knee assist the hamstring to flex the knee and protect the joint and ligaments?

 

We are seeing a decreased use of auto hamstring surgeries in favor of the auto patella tendon or auto quadricep tendon with the athletic population. Is it because the hamstring tendon strength as a graft is failing? (6) Or is it that the rehab to bring the athlete back after hamstring auto graft never truly strengthens the post-surgery hamstring back to pre-injury levels due to the gastrocnemius involvement? Thus the graft failed because the knee didn’t have the protection from hyperextension and valgus forces post-operatively that the hamstring should be able to minimize.

 

More testing and information should be gathered, but at least currently the testing of the hamstring as currently done in most rehab settings should be referred to as knee flexion strength testing, not hamstring strength testing.

 

 

 

 

1. Hamstring-to-Quadriceps Ratio in Female Athletes with a Previous Hamstring Injury, Anterior Cruciate Ligament Reconstruction, and Controls
Eleftherios Kellis, Nikiforos Galanis, Nikolaos Kofotolis
Sports (Basel) 2019 Oct; 7(10): 214. Published online 2019 Sep 28. doi: 10.3390/sports7100214


2. The function of gastrocnemius as a knee flexor at selected knee and ankle angles 
   Li Li, Dennis Landin, Janene Grodesky, Joseph B Myers
  November 2002Journal of Electromyography and Kinesiology 12(5):385-90

3. Actions of Two Bi-Articular Muscles of the  Lower Extremity 
   Landin D, Thompson M, Reid M. 
  J Clin Med Res. 2016;8(7):489-494. doi:10.14740/jocmr2478w 



4. Isokinetic Hamstrings: Quadriceps Ratios in Intercollegiate Athletes
    John M. Rosene*; Tracey D. Fogarty†; Brian L. Mahaffey‡
   Journal of Athletic Training 2001;36(4):378–383

5. Role of gastrocnemius activation in knee joint biomechanics: gastrocnemius acts as an ACL antagonist
M Adouni  1 , A Shirazi-Adl  1 , H Marouane  1    
PMID: 25892616 DOI: 10.1080/10255842.2015.1032943


6. Anterior Cruciate Ligament Reconstruction in High School and College-Aged Athletes: Does Autograft Choice Influence Anterior Cruciate Ligament Revision Rates?
MOON Knee GroupKurt P Spindler  1 , Laura J Huston  1 , Alexander Zajichek  1 , Emily K Reinke  1 , Annunziato Amendola  1 , Jack T Andrish  1 , Robert H Brophy  1 , Warren R Dunn  1 , David C Flanigan  1 , Morgan H Jones  1 , Christopher C Kaeding  1 , Robert G Marx  1 , Matthew J Matava  1 , Eric C McCarty  1 , Richard D Parker  1 , Armando F Vidal  1, Michelle L Wolcott  1 , Brian R Wolf  1 , Rick W Wright  1