The Influence of AlterG Treadmill Training on Lower Extremity Muscle Performance in Cross Country Runners

Abstract

Running on an AlterG® Treadmill (AGT) at reduced bodyweight requires speed to be increased if heart rate response is to match overground running. This can be beneficial as one can run at faster speeds for longer durations, without increasing impact forces or heart rate intensity beyond typical training, all while increasing lower extremity muscle demands. However, it is unknown if AGT training influences lower extremity muscle performance. PURPOSE: Investigate the effect of an AGT training program on lower extremity muscle performance. METHODS: As an offseason supplement, 19 uninjured high school boys cross country runners replaced 2 overground running sessions/week with AGT runs for 6 weeks. AGT runs were 80-85% of bodyweight with speed increased to elicit a heart rate intensity and distance/time consistent with each runner’s mile pace for that day. Bilateral isokinetic muscle performance testing was completed at baseline and post program; 10 concentric/eccentric contractions at a speed of 180o/s for sagittal motions at the hip, knee, and ankle. A 2-way ANOVA (side x time) was used to assess pre-post changes (torque, work, power) and side-to-side symmetry (p≤0.05). RESULTS: Significant interactions were found for almost all hip variables for pre-post and side-to-side comparisons, while both the knee and ankle generally showed no differences. At the hip, the right generally improved pre-post for all variables, while the left decreased. This resulted in side-to-side asymmetries at pre, but improved to mostly symmetric at post. CONCLUSION: The AGT program seemed to primarily influence hip musculature, possibly related to pre-existing asymmetry. However, after training in the AGT environment for 6-weeks, both sides were generally symmetric post-program, mostly due to right side improvements. Thus, AGT training appears to be associated with improved symmetry of hip muscle performance, which may be significant when considering the role of the hip in overuse injuries.Table 1: Outcome variables for the hip flexor and hip extensor muscle groups at pre and post program for the right and left sides. Contraction type (Concentric or Eccentric) indicates the type of muscle contraction performed during isokinetic testing. ^The hip extensors eccentric contraction variables displayed a similar outcome pattern to the extensors concentric, with the exception of mean power where no difference was observed.