With no consensus on the actual meaning and requirements of ‘functional’ training, what does the research have to say on the matter?
'Functional training’ is a term that certainly polarises people in our industry. It seems like every fitness professional and strength coach has an opinion, as well as their own definition of what functional training actually means and what the activity might look like.
It started a few years ago with the move away from machine-based equipment towards a varied approach to training. While some opted to use ground-based equipment in which everything involved the individual standing or creating ground-based forces, others proposed a move towards multiplanar movements that help with connective tissue properties. Others still simply returned to old school lifts with barbells, kettlebells, battling ropes and Olympic lifts. A range of wonderful new ‘functional’ certification courses and training toys emerged, including balancing discs and balls, sandbags, weighted tubes and suspension straps.
The problem of defining ‘function’
The general trend has been for functional training to involve full body or multiple joints, with the person standing; barefoot is often promoted as being equally or more effective than wearing training shoes; using a device that adds load or complexity to the movement which has an emphasis on stability and loading and unloading of muscular and connective tissues through more than one plane. Of course, I mashed together this definition based on recent trends, and the reason I did so is because the true meaning of the term ‘functional’ has been lost or diluted over time. The original idea of functional training was to train the body to better execute the activities performed in daily life.
In reality, the term function varies between activity and between the joints and patterns involved. Some movements require functional stability and others require functional mobility. The problem with reviewing the research into functional training is that the term function has been used broadly to encompass a range of different training outcomes. In most cases, functional training involves exercises for flexibility, balance, core stability, and resistance training. So, in many cases, the typical program prescribed by any personal trainer could be called functional.
Similarly, the term ‘multiplanar’ has a few different meanings. In the true sense, the term refers to movements that cross through more than one of the anatomical planes. Yet multiplanar has also been used to describe multi-directional lunges and hops (Distefano et al. 2009, Begalle et al. 2012), directional movements of the ankle (Bunton et al. 1993, Akuthota and Nadler, 2004), scapular directional changes (McMullen et al. 2000), and directional motion of the knee (Hewett, 2008).
Reviewing the research based around this term also requires a larger scope of work and an ability to differentiate between those directional movements versus planar movements. It appears that this is another term that may be causing confusion in the training community as to its real definition and applicability to training concepts.
Force transfer via myofascial chains is another concept or term that has become part of the functional training vocabulary. It is undisputed that skeletal muscles are directly linked by connective tissue and evidence for the existence of myofascial chains is growing (Wilke et al. 2016). A systematic review in the Journal of Anatomy (2016) suggests that while force transmission along these chains has been hypothesised, there is still a lack of evidence concerning the functional significance and capability for force transfer (Krause et al. 2016). The review suggests that tension might be transferred between some of the adjacent anatomical structures and that the force transfer might have an impact in overuse conditions or on sports performance, but the results were hard to compare due to the varying degrees of structures studied and the histology (microscopic anatomy of cells and tissues) used.
Interestingly, out of the 1,022 studies identified in this field, only nine were deemed to be of high enough methodological quality to be used in the review.
Some recent research into tendon behaviour has also yielded some insight into the viscoelastic properties of these tissues. Earp et al. (2014) found that heavier loads reduced the change in length in knee extensor tendons during the eccentric phase, even though tendon force and rate of force production increased. The authors suggested that during the stretch shortening cycle with maximal loads, tendons will function more like a force transducer, but light loads will actually help to amplify the force by storing energy in the eccentric phase and releasing it in the concentric phase. In a follow up study, Earp et al. (2016) found that when using the same loads, slower bar speeds produced greater tendon lengthening in eccentric phase (viscous behaviour), but faster bar speeds produced greater tendon lengthening in the concentric phase (elastic behaviour).
Functional training for sport
Given the broad context of the use of the term functional, many studies have shown that programs including combinations of flexibility, balance, core stability, resistance training and conditioning will show performance improvements across many sports. Most studies don’t use this term, but there have been a few in which this combination of activities has been called functional. Early studies by Thompson et al. (Journal of Strength and Conditioning Research 2000) for golf, Swanik et al. (Journal of Sport Rehabilitation 2002) swimming, and Ives et al. (Journal of Strength and Conditioning Research 2003) all showed this form of functional training provided benefits to the sporting performance.
More recent studies have been performed, but most are of short duration, low subject numbers or using generic or non-specific measures to assess outcomes. In fact, there are very few strength coaches at an elite level that don’t use these combinations of activities: they simply don’t use the term functional to describe them. For the purpose of this article I reviewed around 40 papers on training for sport in which the above combination of activities was used and there were only a few that used the term functional to describe them. Yet in reality, these activities are commonly used where specific functional changes in flexibility, strength, stability and other areas are required.
Functional training in physical therapy
There has been a large amount of research using functional training in the health and rehabilitation populations. The word functional in these studies has included activities such as those mentioned previously (King et al. 2000, Chin et al. 2004, Weiss et al. 2010), step aerobics (Hallage et al. 2010), and everyday tasks (Manini et al. 2005). Very few studies have explicitly involved the currently accepted version of functional training with a multiplanar element. Previous articles in this ‘Evidence-based practice’ series have dealt with the use of the suspension systems, instability training and balance tools. However, a few specific studies have compared the traditional strength training programs with more ‘functional’ programs where suspension, kettlebell and stability exercises were used. Most of these reported minor differences between the performance outcomes achieved with a mixed outcome reported both for and against the functional training methods (Tomljanović et al. 2011, Pacheco et al. 2013).
In summary, it’s easy to understand how the term functional training has been used differently due to both a lack of agreement over the type of activity typically associated with this form of training and a lack of quality research where current forms of functional training are utilised in a long-term intervention with decent numbers of participants. Until this is improved there is the potential for the term to be used across a broad range of activities, gimmicks and programs with no real evidence to support their use. Fitness professionals need to be mindful of the value of both the term functional, and the methods associated with it, when prescribing such activities for clients.
Dr Mark McKean PhD AEP CSCS is a sport and exercise scientist and Level 3 Master Coach with ASCA. He is Adjunct Senior Research Fellow at USC.