Strength (Video): Resisted Knee Lifts Improve Sprint Speed
Strength (Video): Resisted Knee Lifts Improve Sprint Speed

Strength (Video): Resisted Knee Lifts Improve Sprint Speed

Dick Moss, Editor, Physical Education Update.com

While the Resisted Knee Lift (aka hip flexor exercise) is often neglected in general strength training programs, it is a mainstay of programs designed specifically for running.

But is it really effective in improving the ability to run fast?

A research study at the University of Florida has shown that it is indeed effective in improving sprint speed over 10 yards, 40 yards, and in agility shuttle runs.

The Study
The study involved to 48 college-age subjects who were physically active but not involved in a strength training program. Half performed an eight-week strength program designed to improve hip flexor strength. The control group remained active through this period but were not involved in the strength program.

Performances in four tasks were compared before and after the eight week period.:

  • Hip flexor strength test.
  • 40-yard dash, including split time for the first 10 yards. This measured acceleration.
  • A shutttle run over 4 x 5.8 m. This was considered an acceleration/agility test.
  • Vertical jump height.

Strength Program
The strength program involved three sessions per week for eight weeks of a resisted knee-lift exercise. The resistance was provided by elastic tubing. Subjects performed two sets of 10 repetitions plus a third set to failure. Generally speaking the load in the first two reps was about 75% of one-repetition maximum.

When subjects could complete more than 20 wraps in the third set additional resistance was applied - by using a tube with greater resistance (alternatively, you could move farther from the anchor point).

The reps were performed at a tempo of two seconds lifting versus four seconds lowering, with 30 seconds recovery between sets. The exercise can also be performed in the weight room using the low-pulley machine.

Results
Significant improvements were found in the following areas:

  • Hip flexor strength over the eight weeks increased by 12.2%., with training loads increasing 3-4 times in the first five weeks.
  • Forty-yard dash times improved by an average of .23 seconds, with most of the improvement taking place over the first 10 yards. This was an improvement of 3.8%.
  • Shuttle run times improved by an average of .64 seconds, or 9%.

However, vertical jump height did not improve.

Conclusion
The improvements were considered significant, and any football player who must run the 40 yard dash knows that an improvement of .23 seconds is a definite boost in their performance. A similar improvement for a 100m sprinter would likewise be welcomed.

The caveat is that these results were produced using fit, but untrained subjects. The question is whether similar results can be elicited with trained athletes. This would probably be dependent on their level of hip flexor strength.

However with performance in so many sports dependent upon acceleration abilities: everything from sprinting to basketball, soccer, lacrosse and football, the use of resisted knee lifts in strength programs is recommended.

To see a demonstration of the
Resisted Knee Lift exercise, watch the video below:


Reference: Russell Deane, John Chow, Mark Tillman, Kim Fournier, Center for Exercise Science,University of Florida at Gainsville, "Effects of Hip Flexor Training on Sprint, Shuttle Run, and Vertical Jump Performance." Journal of Strength and Conditioning Research, 2005.
http://www.nsca-jscr.org/pt/re/jscr/home.htm


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