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Importance of Plyometric Training in Rehabilitation
What are Plyometrics?…
Plyometrics are exercises that involve a stretch-shortening cycle of the muscles. This incorporates preparatory and reactive characteristics of the muscles. A simple example of plyometrics is repeated jumping or bounding. The muscles involved will experience phases of stretch followed by immediate phase of reactive shortening. It stimulates two main physiological components: the proprioceptive reflexes (neural side) and the elastic properties of muscle (muscular side). This is highly beneficial when training to return to sports involving high intensity and powerful activities.
Potential Effects of Plyometrics on Rehabilitation…
The use of plyometric training as part of the rehabilitation process does appear to have huge benefits on the outcomes that can determine the effective and safe return to sport following a sporting injury. Whether this injury be upper or lower body (Swanik et al., 2002; Chimera et al., 2004; Zebis et al., 2008). The adaptations associated with plyometrics appear to be neuromuscular in nature and may help improve muscle and joint coordination and control.
The repetitive length and tension changes during plyometrics may stimulate mechanoreceptors, muscle spindles and desensitise golgi tendon organs (GTO). These structures basically send information about muscle length, tension, and stretch respectively to the central nervous system which as a result enhances the awareness of joint position. If the efficiency and stimulation of these receptors is improved and increased through plyometrics then the connection between mind and muscle will be improved hence the improvements in coordination and joint control.
Plyometrics is also said to help improve power output and be useful to include when aiming to improve strength and power. Without delving into the vast amount of literature in a general exercise setting for this there is little evidence regarding this proposal in an injury or rehabilitation setting. General evidence for the benefits of plyometrics in a rehabilitation setting is also limited however the following studies offer positive evidence for its use in injury rehabilitation.
Does Plyometrics Actually Help?…
Including plyometric exercise in shoulder rehabilitation programs, targeting the rotator musculature seems to improve proprioception and kinaesthesia. Basically plyometrics improves the joint position sense in injured athletes and their awareness of the position and movement of body parts (Swanik et al., 2002). These results may suggest that the inclusion of plyometrics may help retrain and develop neural adaptations both in the central and peripheral nervous system
The neuromuscular adaptations stimulated by plyometrics appears to alter the coordination and how the motor units are recruited. These adaptations then improve muscle pre-activation and control during high intensity explosive movements. For example Zebis et al. (2008) found that plyometric training increased the activity of certain muscles (Medial Hamstring) during a side-step or cutting movement, this then reduced dynamic “bowing-in” of the knees. Similarly, alterations in preparatory adductor muscle activity and muscle co-activation of the hip adductors and abductors appear to occur as a result of plyometrics (Chimera et al., 2004). These adaptations will help improve the dynamic restraint and control over joint actions.
Plyometrics did not seem to improve peak torque when compared to traditional weight training. However, its inclusion has importance in developing neural adaptations and therefore is still imperative for the safe return to sport. To achieve the strength gains required to return to sport traditional resistance exercises should also be included in any rehabilitation program and combined with progressive plyometric exercises (Swanik et al., 2002). However there were improvements in torque decrement, so through improved muscle efficiency and coordination they were more able to maintain torque in prolonged bouts of exercises. This may then suggest that increased neuromuscular efficiency and coordination may help decrease the onset of fatigue and assist with functional stability and dynamic restraint throughout an exercises/activity duration.
How Do Plyometrics Apply to a Return to Sport?…
The ability to detect small changes in joint position and muscle state will be enhanced through plyometrics. This is facilitated by improvements in mechanoreceptor and muscle spindle stimulation which optimises the connection between mind and muscle therefore the athlete is constantly more aware of muscle and limb state and position. If the athlete is more aware of their limb and joint position, and capable of altering limb position effectively during their sporting activities they are less likely to adopt “injury prone” postures and positions.
Not only will plyometrics enhance the ability to detect these changes they also produce adaptations that aid the athlete in physically dealing with any alterations in limb and joint position. The way muscle motor units are recruited adapts to plyometrics and the coordination of muscle contraction is optimised. This improves muscle pre-activation and co-activation of muscles around the joints during high intensity movements, this in turn improves control and dynamic restraint. With more control, restraint, and optimal, synchronised muscle activity joints and limbs will be more stable and protected from re-injury during explosive movements.
Despite there being limited evidence for strength gains in a rehabilitation setting, an improvement in torque decrements has been reported. This means that if the athlete is more fatigue resistant and able to maintain sufficient torque for prolonged activities, such as their sport, they are less likely to experience drops in joint control and leave themselves prone to re-injury.
What to Consider During Rehabilitation…
The ultimate goal for both athlete and therapist is to get the athlete back to playing their sport as soon as is safely possible. To ensure this safe return the athlete should meet criteria to return and the therapist should consider the following:
• Physiological Healing Process – has the athlete had enough time to progress to late stage healing?
• Pain Status – Has pain diminished? Is it likely to be pain free during sport?
• Swelling – Has the swelling gone? Is it likely to reoccur with sport?
• Range of Motion – Is their ROM adequate for safe return to sporting demands?
• Strength – Are they strong enough for sporting demands?
• Neuromuscular Control/Proprioception/Kinaesthesia – Do they have adequate awareness and control over body movement?
• Cardiovascular Fitness – Are they “fit” enough for the sporting demands?
• Sport Specific Demands – Have they relearned sport specific skills adequately?
The above considerations will not all be covered by plyometrics alone. However, without them will the athlete sufficiently gain neuromuscular control during explosive and demanding activities? If what the evidence suggests is true then plyometrics will play a huge part in preparing the athlete for return to these demanding activities of their sport.
Plyometrics are generally used in the late stages of rehabilitation, but like other training modalities plyometrics can be applied in a progressive manner. I try to include low level plyometrics as early as the healing process and pain allows. I have found that plyomterics does develop both power improvements as wells as increased control during these movements. When working with athletes who are involved in power or strength based sports such as Rugby this element plays an important part in their successful returns.
One thing I have noticed with athletes I have worked with is how sport specific these exercises need to be when working with athletes. Athletes I have worked with who have had past injuries that have been treated by other professionals have received physical therapy and advice which has successfully treated the injury and prepared them for general daily activities. However, once they step foot back on the field and are placed in environments that aren’t present in daily activities they suddenly have a re-occurrence or don’t feel as ready as they first thought. This doesn’t mean to say the injury hasn’t been treated successfully. However, when working with athletes we need to consider the environment they are going to be competing in. If we can replicate the stresses they encounter in their sport then when they come to experience these stresses they will be more prepared and trained to cope with these stresses.
For example I had a player who had a long standing ankle injury, he had been treated very well in the past and put through general exercises. Day to day he felt no instability or pain. However, on a regular basis on the rugby field he would roll his ankle or experience discomfort. When questioned about specific tasks that brought on these incidents I found that landing, from being lifted, in lineouts or sidestepping were the main culprits. Therefore we included plyometric and proprioceptive movements that replicated these activities to help him train in these environments to help optimise the stability, control and strength during these tasks.
This highlights that to have a truly successful rehabilitation program and a successful return to sport a therapist has to assess the demands of the sport and position of the athlete. They also need to be creative when designing exercise programs and not simply fall into a general protocol.
Case Study – Groin and Hip tightness and pain
• Recreational Gym User; 3-4 x per week
For the purpose of this case study the client will be given the pseudonym Steve. Steve contacted me via his personal trainer who had informed me that Steve was experiencing chronic pain in his groin region of his hip, and was struggling with his range of movement (ROM) during squatting, lunging or stepping activities. On assessment there was a lack of mobility and range of movement around the hip in which his abduction, flexion and rotation was restricted. There also appeared to be a weakness and inactivity of the gluteals which was evident during Steve’s squat assessment during which there was a lack of control and stability of the pelvis. These findings gave me a starting point for the treatment and path I was going to take with Steve.
Soft Tissue Massage…
We started by addressing the muscular tightness evident in the adductors. I started by applying effleurage techniques to the adductor complex to warm up the muscle before starting to apply some deeper pertrissage techniques using my thumbs, palms, fists and elbows. These involved stripping the muscles, cross and circular frictions, wringing and picking of the muscle and some fascial stretching. On palpation the muscle did appear to respond positively and became much more pliable and an obvious relaxation of the tight muscle was observed. After several initial sessions of soft tissue massage and release Steve reported significant improvements in his subjective feeling of pain and tightness. There were also noticeable improvements in the ROM of Steve’s hip, He demonstrated the improvement in his lunging ROM and Squat.
Proprioceptive Neuromuscular Facilitation (PNF)…
To complement the soft tissue massage I introduced some PNF to our sessions to help further release the still tight adductors. This is a stretching technique involving some active involvement by the client which stimulates certain reflexes within the muscles to aid relaxation. To do this Steve laid supine and one leg was abducted whilst stabilising the femur to prevent excessive external rotation, whilst the other hand stabilised the pelvis to prevent excessive lateral flexion or rotation. The hip was abducted and control by using my bodyweight to move the hip through this movement.
The adductors were placed on stretch and held for 15 seconds, Steve was then instructed to maximally adduct his hip against me isometrically (statically). This contraction was held for 12 seconds to allow for autogenic inhibition (relaxation response to the held contraction). After the contraction the leg was allowed to relax briefly before reapplying the passive stretch for 15 seconds. After performing 3 sets on each leg after the massage, there was additional improvement in the ROM and noticeable muscular tightness.
Rubini et al. (2011)
This study examined the effects of static and PNF stretching on the flexibility of the hip adductors in female ballet dancers. Subjects performed 4 sets of either static or PNF stretches, the control simply rested for the duration of stretching sessions.
The results show no difference in the outcome between static or PNF stretching, both produced significant improvements in ROM of the adductors. This highlights that both static and PNF stretches produce the desired outcome.
Interestingly this was conducted on ballet dancers who already possess high levels of flexibility. Despite their already high flexibility, significant results were observed as a result of stretching, therefore if utilising both static and PNF stretching with my client, who has/had very limited flexibility then there may be a more amplified result or even additional result of combining the two to his program.
In addition to the PNF I decided to try using some Muscle Energy Techniques (MET’s). The aim of this was to produce reciprocal inhibition in the adductors. By contracting the hip abductor muscles through a movement then the idea is that the antagonistic muscle group i.e. the adductors will relax allowing greater movement. Steve was instructed to take the same position as the PNF and his leg stabilised in the same way. This time while the leg was abducted actively and Steve was instructed to abduct the leg applying approx. 20% force against my resistance. The leg was still allowed to move through range of abduction. 2 sets were applied to each leg, and again positive improvements were observed.
There appears to be limited evidence for the use of MET’s on hip mobility and ROM. However some studies conducted on other joints have revealed positive results.
Moore et al. (2011)
This study observed an improvement in horizontal abduction and internal rotation at the glenohumeral joint after a single application of METs to the horizontal abductor muscle group. An MET to the external rotators did not produce any significant differences however. The reason for this lack of significance may be that the use of only one stretch and targeting only one group of muscles may not address the global restriction to the movement being investigated.
This study only used one MET and stretch whilst assessing several movements therefore it may be expected that not all movements will be significantly improved without targeting the specific muscles associated with each movement. In my case I targeted the adductors, which limit abduction and external rotation (the movement my client was restricted in) therefore observed positive results. Therefore based on my experience and some of the evidence in the literature it would appear that applying METs to specific muscles associated with the target movement will have positive results on ROM and mobility.
As I discovered the glutes and posterior chain appeared to be underactive and was placing greater responsibility on the adductor complex and anterior chain to stabilise the trunk and hip during activities. This may be a contributor to the dysfunction and symptoms experience by Steve. Therefore I designed an exercise program for Steve to include in his current workouts and warm ups. These involved various stretches and exercises designed to achieve greater ROM and release in tight overactive muscles, and activate the weaker underactive muscles.
These stretches were chosen to lengthen the tight structures and anterior system components which appeared to be overactive in Steve’s case.
• Sitting Short Adductor Stretch
• Sitting Long Adductor Stretch
• Kneeling Hip Flexor Stretch
• Dynamic Side Lunge Stretch
• Open-Close Gate Stretch
• Active Oblique Stretch
Isolated Activation Exercises…
The aim of these exercises was to activate the deep core muscles and the posterior chain. The goal was to increase posterior muscle activation to help stabilise the hip and trunk during activities to reduce the responsibility on the anterior structures.
• Prone Lying Straight Leg Glute Extension
• Kneeling Dog Leg Lifts
• Single Leg Toe Touches (Deadlift)
Steve was advised to avoid excessive isolated activity of the anterior core muscles and the adductors. The following exercise progressions were chosen to combine the activation of the posterior systems musculature i.e. the Gluteals, Latissmus Dorsi, and Thoracolumbar Fascia. The aim of these exercises is to encourage this system to stabilise the core and hip complex during whole body exercises.
• Squat to Row
• Split Squat to Row (double and single hand)
• Reverse Lunge to Row
Exercise selection and design was based upon the work of Brent Brookbush who describes the subsystems of the body and highlights that there is potential for an over-activity of the Anterior Oblique Subsystem (AOS – Obliques, Opposite Side Adductors) in Hip Dysfunction. He also highlights potential for this to be combined with an under-activity of the Posterior Oblique Subsystem (POS – Latissimus Dorsi, Opposite Side Gluteals and Thoracolumbar Fascia).
Therefore when observing Steve’s highly tight anterior chain and weakness of the glutes this approach seemed to fit my case hence the selection of the exercises. The above exercises are all designed to target these under-active areas whilst training whole body stability and limiting the activation of the anterior structures and replacing this with the release and stretching techniques described earlier.
There are several studies showing that stretching, PNF and MET’s techniques produce desired outcome in ROM in various joints and body areas. However one study caught my eye and supported my approach of including many approaches and integrating the whole body into the treatment of my client.
Moreside & McGill (2012)
The authors compared four groups of young men with limited hip mobility. These groups consisted of 1) stretching, 2) stretching with motor control exercises, 3) core endurance with motor control exercises, 4) control group. Six-week programs were assigned to each group including the hip ROM stretches and exercises, movement pattern exercises, and timed-core endurance exercises.
Interestingly the two stretching groups achieved significant improvements in hip ROM and mobility. The core endurance and motor control group also improved hip ROM and mobility but only moderately in rotation. There was no improvement in the control group.
This study therefore supports the notion of combining isolated stretching techniques with whole-body and core stability exercises to improve dysfunction and ROM in the hip joint. This may encourage more of global approach to treating musculo-skeletal dysfunctions rather than an isolated, and single structure focused approach.
Steve’s Progress to Date:
Since our first session where Steve was reporting regular pain and stiffness throughout the groin and hips. He has progressed significantly since then, in the 3 months I have been regularly treating Steve he no longer experiences episodes of “groin” pain. He has also reported and demonstrated significant improvements in both ROM and muscular control of his exercise activities. For example his posture, stability and control during squatting movements have improved considerably. His personal trainer has also commented on Steve’s new found ability to perform exercises pain free and achieve a much greater ROM. Steve is now including a wider repertoire of exercises into his workout that in the past would have been impossible or severely restricted by pain and a lack of mobility.
We are continuing to regularly loosen off his legs but in as more of a general “MOT” of the lower body musculature to ensure that the positive effects are maintained. Therefore it would appear that the combination of treatments and exercise approach has had a positive and prolonged effect on Steve’s complaints and restrictions to activity.
Moore, S. D., Laudner, K. G., McLoda, T. A. and Shaffer, M. A. (2011). The immediate effects of muscle energy technique on posterior shoulder tightness: A randomized controlled trial. Journal of Orthopaedic & Sports Physical Therapy, 41 (6), 400-407.
Moreside, J. M. and McGill, S. M. (2012). Hip joint range of motion improvements using three different interventions. Journal of Strength and Conditioning, 26 (5), 1265-1273.
Rubini, E. C., Souza, A. C., Mello, M. L., Bacurau, R. F. P., Cabral, L. F. and Paulo, T., V. (2011). Immediate effect of static and proprioceptive neuromuscular facilitation stretching on hip adductor flexibility in female ballet dancers. Journal of Dance Medicine & Science, 15 (4), 177-181.