Curved non-motorized treadmills (assault-runner and similar) have become popular in gyms, especially for cross-fit style training. While running on a regular treadmill doesn't have much difference compared to outdoor running, the curved treadmill feels different.
The question: can we use the curved treadmills and how?
To answer this questions we need to take a look at 3 parts: cardio-vascular demand, muscular adaptations, effect on running technique.
1️⃣ Cardio-vasular demand
According to one Australian study [3], cardiometabolic demand is higher on a curved treadmill compared to overground running. Running economy is also depends on body weight. For lighter runners it's harder. This means that we can't set the training plan by pace, better to go by HR
2️⃣ Muscular adaptations
A study [2] showed that curved treadmills develop quadriceps more than hamstrings compared to a flat treadmill. This makes them useful for trail runners or as a substitute for hill running. In the base period, they can also work as cross-training
3️⃣ Running technique effect
Common sense tells us that running on a curved treadmill is biomechanically different and this study proves it [1]. Is it good or bad? Examples from other sports shows that it can improve the technique in long term buy may have short term negative effect
4️⃣ Additional benefits
- No scientific proves for now, but it seems like curved treadmills are easier on joints. It makes it safer for runners without proper technique, and good for those who return after injuries
- Changing pace is more convenient which makes these treadmills great to train sprints and do variations of VO2max workouts
Conclusion:
- Curved treadmills can be a good tool in the base period as a cross-training to keep up aerobic volume without additional impact for joints; safer for beginners; good for trail runners and to substitute hill training; convenient for VO2max intervals
- Curved treadmills should be used with caution closer to races; they may temporarily impact the running technique and shift the muscle balance away from hamstrings toward quads