The recent review by James Fisher, James Steele, Stewart Bruce-Low and Dave Smith should be on the “must read” list for everyone with an interest in exercise. In fact, you should download and read it before you read the rest of this post which is the fourth of several commentaries I will be writing on their review.
Resistance Types, Free Weights and Machines
Over the past twenty years I have used and trained people with free weights, body weight, manual resistance, and a variety of plate-loaded, selectorized, and motorized machines, including some of the best and worst ever made. While each has it’s advantages and disadvantages and I have my preferences, in my experience how you train is far more important than the equipment you use. As long as you train hard, progressively, and consistently you can get good results using any of them. This isn’t just my experience or opinion, though. The Free Weights and Machines section of the paper begins,
Research has reported no significant difference in strength gains between groups training on resistance machines and undertaking free weight exercises [77-79]. Other research has utilized a leg extension machine but compared variable to constant resistance (by switching between a cam and a circular disc), once again reporting no significant difference in the strength increases between groups .
Whatever advantages different types of equipment may have, none can claim to produce better general strength gains (as opposed exercise specific skill improvements, which many people tend to confuse for increases in strength).
Contrary to the claims of free weight proponents the additional balance required during free weight exercises does not increase neural activation and exercise effectiveness. One study mentioned showed force production in the target muscles may even be reduced when additional balance is required. It is also important to note that balance is not a general skill but specific to particular postures and movements, and improving the skill of maintaining balance during a free weight exercise does not transfer to improved balance in other activities.
Contrary to the claims of many machine proponents the balanced variable resistance provided by some machines may not provide better strength increases than constant resistance, or by extension other equipment and modalities which provide less “congruent” resistance curves (read Constant vs Variable Resistance Knee Extension Training). Some might argue either the repetition speed was too fast for meaningful loading with any cam (subjects followed the traditional Nautilus protocol of a two second lifting and four second lowering cadence) or the cam used wasn’t actually properly balanced to the resistance curve (they used a Nautilus Leg Extension machine which some people believe doesn’t provide enough of a resistance “fall-off” towards the end point when used with controlled speeds), or both. Speed of movement does affect resistance curve requirements – the faster the speed the less resistance needs to fall off because the extra is necessary to balance out the additional kinetic energy imparted during positive acceleration at the start of the positive.
The theory that using a machine or exercise technique which balances the resistance to the strength of the muscles over the full range of joint motion of an exercise is more effective is based on several premises. It is assumed that strength gains are specific to the positions or portions of the range of motion trained. It is assumed that continuous loading results in more efficient inroad thus faster motor unit recruitment, greater metabolic demand, and more efficient achievement of momentary muscular failure (100% intensity). The effectiveness of isometrics and rest-pause training throws a huge wrench in this.
I’ve read different studies on isometrics which show a range of specificity of strength gains from within around fifteen to twenty degrees of the position trained to full range of motion. Some times the results varied significantly between individuals within a study. Based on my experiences with various isometric protocols over the years, including Mike Mentzer’s static holds, John Little’s static contraction training and Max Contraction, and Ken Hutchins timed static contraction, I believe strength gains from isometrics result in full range strength increases in most exercises. The exceptions might be exercises where the relative involvement of different muscle groups varies considerably over the full range of the exercise if the isometric exercise isn’t performed in a position where the majority of these are significantly involved. Even if this is the case for some exercises, as long as the overall routine effectively addresses all the major muscle groups it shouldn’t be a problem. I suspect the specificity has more to do with skill in the specific exercise performed and testing equipment and that if a muscle gets stronger in any position, it is proportionally stronger in all positions in general task performance.
I’ve had good results with rest-pause training and in an identical twin experiment I performed the twin who did rest-pause had a slightly greater strength increase than the one doing continuous repetitions. Unloading and resting the target muscles between repetitions didn’t hurt her progress at all. You can’t say it’s less effective. The only thing that might be considered a negative is significantly more weight is required to achieve momentary muscular failure with the same number of repetitions or in a similar duration, and this could be considered less efficient and also increases the stress on all the tissues involved (which is an important concern when you are working with frail or injured subjects).
We don’t need perfectly balanced variable resistance. We don’t need continuous muscular loading. While these things might provide an advantage over the long run in terms of efficiency or rate of progress it appears to be possible to achieve equally good results without them. Perhaps this is because as long as the effort is high enough and the load is adequate to achieve momentary muscular failure within a reasonable time frame it all averages out? Like many factors, there is probably a point of diminishing returns beyond which these things stop making a difference. Maybe, as long as the cam or technique used provides a resistance curve that roughly approximates the strength curve without any huge sticking points that’s all we need?
This doesn’t mean I don’t think there are advantages to training with properly designed machines. Since I plan to write a lot more about this elsewhere I’m not going to go into it in detail here, but a properly designed machine allows you to train more safely and more efficiently, and some muscles can only be worked directly with machines which is necessary when working with certain injuries, conditions, and physical limitations. I prefer machines for these and many other reasons. When it really comes down to it though, like I’ve been saying all along, how you train is far more important than the equipment you use.