Preseason Training and Your ACL

You will often hear that preseason training will prevent ski injury. In many cases, that's true, but sadly, no exercise will guarantee that you won't tear and ACL. Here's a brief presentation of the available research on training levels and ACL injury for skiers.

In brief

The short answer is no. Some researchers have shown that jump training can reduce injury rates among females in basketball and soccer (more on basketball weightlifting programs). Even those researchers, however, concede that skiing is quite a different matter and the leading authorities on ski injuires say there is no correlation between preseason training and injury reduction. So preseason training will make you stronger, but it's not going to prevent ACL injury.

Some background: studies of basketball and soccer players

Women have a much higher incidence of ACL injury in most sports. Epidemiological studies show this to be true for soccer, basketball, skiing and other sports. According to the American Academy of Orthopaedic Surgeons, "nearly 60 percent of ACL injuries in female basketball players occur when landing from a jump" and "female athletes participating in certain sports like soccer or basketball are three- to four-times more likely to injure their ACL than males."

Some studies have argued that compared to men, women tend to rely on ligaments more than muscles for knee stability, they tend to bend less at the knees and waist when absorbing an impact (and thus generate higher forces) and many have a tendency to let their knees cave in to the inside when jumping and landing. Women also have anatomical differences that contribute to higher rates of anterior cruciate ligament (ACL) injury. The hips being relatively wider, female legs have a greater Q angle, that is the lateral angle between the upper leg and lower leg.

Women have one more set of problems according to some researchers. The ratio between the strength of hamstrings and the strength of quads tends to be lower in untrained women than in men. In other words women's hamstrings tend to be relatively weaker than men's in relation to their quads. Ideally, the hamstrings should be at least 60% as strong as the quads to prevent ACL injury. Furthermore, muscle firing patterns are different. Untrained women tend to have an imbalance between when the quads and hamstrings fire, but through training can improve coactivation of the muscles, which again is important for knee stabilization. Because of this second point, it appears that plyometric jump training is especially effective for women, whereas men can get by with simply strengthening the hamstrings. Researchers (Hewett et al.) have found that a three-phase jump training program can bring women to the same levels of strength and coactivation as men. The six-week program involved sessions of 60 to 90 minutes, three days per week. Athletes started with two weeks focussed on technique. In phase two, athletes tried to build strength and agility. In these two phases athletes did as many jumps as possible using proper technique. In phase three, the athletes focussed on maximum vertical leap, in other words explosive force [12, 3].

The program used in the Hewett study involved a wide variety of jumps, combined with stretching and weight lifting. A complete description of the program is available online.

All that said, some researchers have questioned the Hewett findings, arguing that their results do not support their conclusions[4]. Fagenbaum et al. found no difference in hamstring activation and knee flexion between men and women. That finding, however, pertained to a small group of college athletes, so the high level of training among the females may make them more similar to the females trained by Hewett, rather than the untrained women in the Hewett study[5].

What about skiing?

Epidemiological evidence shows that female skiers have a higher incidence of knee injury than male skiers. The best current research specific to skiing, based on prospective rather than retrospective studies, indicates however that gender is not as good an indicator of risk for knee injuries from skiing as it is for other sports or as had been indicated for skiing based on retrospective studies[6]. That study, however, was based on full-time ski professionals, so as in the Fagenbaum study, the female skiers are perhaps more like Hewett's "trained" female athletes. Either way, even Hewett agrees that skiing "skiing is a different animal than other sports." Bob Johnson, director of the longest-running study of ski injuries in America (and my former next-door neighbor back in the day), says regarding preseason conditioning as a means to prevent injuries: "Many claims have been made, but none have ever been proven." He adds: "World-class skiers have the highest ACL injury rates, and they're the best trained and the strongest"[7].

Is there anything you can do?

Yes, you can carefully study the materials from Vermont Safety Research on Knee-Friendly Skiing. It's not about what you do in September, but what you do when you find yourself in a risky situation.

Cited Sources

  1. "Women and ACL Injuries" from the American Academy of Orthopaedic Surgeons (2002), link.
  2. "Preventing ACL Injuries in Women" from the American Academy of Orthopaedic Surgeons (2000), link.
  3. TE Hewett et al., "The Effect of Neuromuscular Training on the Incidence of Knee Injury in Female Athletes. A Prospective Study," The American Journal of Sports Medicine 27:699-706 (1999), link.
  4. Letters by WG Clancy, The American Journal of Sports Medicine 28:615-616 (2000), link; S Lyman and S Kirkley, The American Journal of Sports Medicine 28:918-919 (2000), link; and T Ashikaga, The American Journal of Sports Medicine 28:919-920 (2000), link.
  5. R Fagenbaum et al., "Jump Landing Strategies in Male and Female College Athletes and the Implications of Such Strategies for Anterior Cruciate Ligament Injury," The American Journal of Sports Medicine 31:233-240 (2003). Link.
  6. RW Viola et al., "Anterior Cruciate Ligament Injury Incidence Among Male and Female Professional Alpine Skiers," The American Journal of Sports Medicine 27:792-795 (1999), link.
  7. L Schnirring, "Training Programs May Lower Women's ACL Injury Risk," The Physician and Sports Medicine vol. 27, no. 10 (1 October, 1999), link.