With 14% of United States runners preferring to train on an motorized treadmill (MT), many clinicians using the MT as a tool in gait-retraining, and its role in the collection of sports science data, it is important to understand the differences between running on an MT and overground(1). A group from the Netherlands wondered what the... MORE
Why athletes with patellofemoral pain should skip their workout
Runners suffer injuries at an alarming rate. Up to 80% of runners will report an injury each year! Most injuries are due to the inability of tissues to handle the loads applied to them. Often this is due to training error such as increasing distance or pace too quickly or taking on an aggressive hill-climbing regimen. These assertive increases in load are outside of the “envelope of function” or the tissue’s capacity to handle the load, repair itself, and strengthen for the next activity. As Alicia Filley explains, researchers from West Virginia surmise that interrupting tissue homeostasis around the anterior knee causes the discomfort of patellofemoral pain syndrome(1). They recommend keeping all rehabilitation activities within the “envelope of function” so as not to further irritate the tissues. For athletes with patellofemoral pain, this means altering anterior knee loading.
Decreasing loads so all activities lie within the pain threshold seems like a good idea, unless the athlete is midseason and doesn’t want to lose their fitness threshold. In this situation, researchers from North Carolina suggest athletes skip their workout. That’s right! These sports scientists believe that skipping may be the best option for an athlete seeking to decrease lower extremity loading while maintaining a high level of fitness(2).
To test this theory, 20 healthy recreationally active adults participated in a skipping training program. While most of us remember skipping from our playground days, the researchers spent three separate days reviewing the technique with the participants. They ensured subjects were comfortable with the form and that any novelty movement patterns were eliminated. They even performed one-mile sessions on a treadmill!
Researchers first tested the metabolic demands of treadmill skipping and compared this to the needs of the same subjects while running on a treadmill. They then collected data on motion and force production using video gait analysis and force plate readings while skipping and running overground. The subjects skipped and ran at a similar pace – about 10 minutes per mile.
Here’s what the researchers calculated for both running and skipping trials:
- Forces produced by the hamstring, quadriceps, and gastrocnemius muscles
- Tibiofemoral and patella-femoral joint contact forces
- Shear tibiofemoral joint contact forces
Skipping steps are shorter than a running stride; therefore, the study reported the results in both per step and per kilometer formats. They found that the contact forces at the knee joint were significantly higher per step when running. Notably, peak patellofemoral compression forces measured more than 250% higher in running when compared to the contact of the trailing skipping leg.
The researchers found that participants executed 910 steps per kilometer while running, but utilized 1139 when skipping. Therefore, they calculated the forces per kilometer and discovered that peak patellofemoral forces averaged 37% higher in running compared to skipping, even when the extra steps were taken into account.
The metabolic demands of skipping proved 30% more than that of running. This means skipping required the athlete to expend 30% more calories than running at the same speed. The higher metabolic demand was strongly associated with the vertical displacement of skipping. Adding in the vertical component makes skipping a more demanding aerobic activity.
Athletes who suffer from patellofemoral pain can decrease their anterior knee load by skipping. The enhanced aerobic aspect of skipping means they can further reduce the time or distance while maintaining their fitness level. Since keeping injured athletes moving within the “envelope of function” without exacerbating their pain is the goal of rehab, skipping the workout might prove the best thing for patellofemoral pain.