In The Lab: Do Exercise Machines cause Injuries?
1)Please introduce yourself;
Cory Hofmann, M.S.
Senior Biomechanics Engineer for Life Fitness Inc.
Teaching Fellow for Cybex Research Institute
2)What research projects are you currently involved with?
My main research projects right now involve investigating the influence of treadmill suspension mechanisms on running biomechanics, and determining a methodology for measuring lower body force profiles experienced when using cross trainers (elliptical trainers, Arc Trainer, etc.).
3)What have you learned from your current study?
I’ve learned that shock (the rate of deceleration on ground contact) is not always the best indicator of how a surface ‘feels’ to a user. The reasons for this are complex - different people tend to run differently (news flash!) and humans are good at slightly adjusting their running patterns in response to different running environments. For example, running on a harder surface usually results in greater hip and knee flexion, perhaps to absorb or dampen some of the impact associated with initial contact. I believe that these subtle changes that the runner makes in response to the surface will play just as big of a role as the mechanical properties of the surface itself in determining the ‘feel’ of a treadmill.
4)How often does the data you collect surprise you in terms of contradicting your initial hypothesis?
Quite often. The human body is an amazingly complex thing. For example, in the above research investigating treadmill suspensions, I was surprised by how many people could not even tell that some of our experimental conditions were treadmills in which the shock absorbing elements had been replaced with steel blocks.
7)How is the research you are involved in have an impact on the general public?
I’m fortunate to be in a position where my research often feeds directly to engineering teams responsible for designing our cardiovascular or strength training fitness equipment. Therefore, often when an exerciser uses one of our products, their experience is often directly determined by our research and design efforts. I also get the chance to perform ‘blue-sky’ research which doesn’t directly contribute to product design, but often fuels our educational offerings.
8)Many health clubs are following a recent trend of pulling out “exercise machines” such as chest presses, shoulder presses, lat pull down machines, etc in favor of opening up floor space so people can do more bodyweight and unstable surface training. The general idea behind this is that exercise machines, which may focus on moving a single joint, can isolate muscles. This muscle isolation then creates muscular imbalances which causes motor control dysfunction thereby setting up potential injury. Does your research tend to support this line of thinking?
Machines don’t create muscle imbalances, poor programming does. There are few strength training machines that are capable of truly isolating a single muscle – a group of agonists, sure. However, even in a machine environment, you’ll see antagonist muscle activity at the end of the range of motion if an exercise is performed at a high velocity. This is referred to as tri-phasic muscle activity and it’s something that has been researched for decades. The argument continues to break down even more when considering the numerous machines that are multi-joint, like the ones mentioned.
In my opinion, the fitness industry has moved away from its fundamental principles in exchange for the exotic. The key principles like SAID (specific adaptations to imposed demands) with considerations of FIIT (frequency, intensity, type, and time). Exercise aren’t good or bad, they fall on a spectrum depending on the specific imposed demand, how it has been progressed/regressed, and the specific objectives of the exercise for the individual.