The Question of Returning To Play

“Early return to sport has poor odds for success and is likely to fail in a large proportion of cases.”

I coached a dedicated group of boys for two years. Their dedication was such that, even though I introduced some new techniques which were difficult for them; taught and held them accountable in ways that were different from what they were used to, they showed up to play anyway. At the end of my time with them, we won the tournament held in our backyard for the first time. A look back to those days...

Their dedication also extended to wanting to play, even when they were injured. One practice, one of my midfielders showed up with roadburn down his side- he fallen off his skateboard and slid a few yards. Another one was involved in a crunching tackle. We had to lift him off the pitch in the second of three games at a tournament for which we had woken up before dawn to make. two minutes later, he was doing his best impression of courtesy while demanding that I put him back on the field. There were many of these in the time I was with them; but this is not the impetuous spirit of 14- and 15-year-olds. I managed significant trauma to my own hamstrings during a match and insisted on playing the next match. It was six days from the first injury. Plenty of time to rehab- or so I thought. It was not until the 6 months had gone by, and the next season was under way before I was confident enough to sprint the like I used to. The hamstrings were well and healed, but I kept thinking, "What if it happened again?"

Without reservation, this is an issue faced at the highest level, where players need to play to keep their spots on the team, and managers need them to play to win championships. The result is players and managers who have to deal with the frustration of injury and re-injury.

Function vs. Time- When Can I play...

While research shows that regeneration would still be ongoing up to and over 3 weeks since the initial injury, early return to sport is often proposed when players have suffered a hamstring injury. It is no wonder that the recurrence rate for hamstring injuries is so high. Part of the issue is that hamstrings have been shown to be most susceptible during the late swing phase of high speed running/sprinting. Jogging with barely a burst of speed constitutes most of the 'tests' that athletes have to pass before being allowed to return to play. However, the eccentric capacity of the hamstrings is not tested under these conditions. Team practices are very controlled with less competitiveness, speed and the kind of muscular fatigue that players experience during actual match play. Therefore, even when players 'successfully' navigate practice, they may still be unprepared for the rigors of first team play. Indeed, complete recovery could still be months away. Peterson at al, (2010) suggested that a player with a recent hamstring has 15 times the risk of injury in a match as he or she does a training session. According to Askling et al., (2006) Isometric hamstring muscle strength in sprinters was 70% (2 weeks), 85% (3 weeks) and 90% (6 weeks) that of the uninjured limb after an initial hamstring muscle injury. A range of 6-50 weeks was observed before the same set of players felt they were back to the level they were before getting injured. Both athletes and managers report reduced performance when players return to play early, both in a physical and mental capacity.

Specific criteria need to be established before players can return to play, measures that can help determine the readiness of players to resume play, and thereby reducing the risk of re-injury. These will measure how well the hamstrings perform in a fashion akin to that of competition (function) rather than being based on the question of how long its been since the incidence of injury (time). The following have been proposed:

• Hamstring strength recovery 
• Hamstring flexibility 
• H:Q ratio 
• self-reported insecurity/pain during ballistic hamstring flexibility movements (Askling's H-test) 
• high-intensity running performance 

Other tests certainly exist at the highest levels where teams have physiotherapists, athletic trainers, fancy equipment etc, which are not readily available to coaches like I was at U14/15. For those coaching at grassroots, the Nordic hamstring exercise is all but the holy grail. It requires no equipment, can be taught easily, and when used appropriately, has produced some spectacular results.

Can One exercise really make a difference?

The effects of the exercise on acute hamstring injury as well as on re-injury were investigated (Petersen et al, 2011) with 924 soccer players. In a carefully structured, progressively overloaded 10-week program, injuries both new and recurrences were reduced by 70% and 85% respectively. The investigators concluded that this preventive effect was solely due to the Nordic hamstring exercise. (Petersen et al, 2011) Moreover, the study showed that in order to prevent one re-injury, only three players at high risk (players with a hamstring injury in the previous year) had to perform the program. Thus, the number needed to treat (NNT), is much lower than the threshold considered acceptable in cardiovascular diseases or cancer where 10–100 or more is often celebrated (Slider et al., 2008) and around 90 athletes for ACL injury training programs, including neuromuscular work. (Grindstaff et al., 2006)

These findings concur with Arnason et al., (2008) whose own 10-week intervention produced a 65% lower injury incidence in soccer players. This intervention consisted of warm-up stretching, flexibility training and the Nordic hamstring exercise program, compared with a group performing warm-up stretching and flexibility training alone.

A 2002 paper by Croisier et al., reported a 100% success rate (no re-injury the following year) after introducing progressive isokinetic strength training (including both concentric and eccentric contractions), performed thrice weekly. This was continued until hamstring strength and eccentric strength deficits normalised from 4 to 10 weeks.

Why it works... briefly.

The Nordic hamstring exercise addresses the eccentric strength deficits which are undoubtedly present following injury, if not the cause of the initial injury. Recall that most injuries occur when the hamstrings are in their lengthened state (during eccentric contraction).

Taken together with Petersen et al's data, systematic and progressive eccentric strengthening has a large hamstring re-conditioning capability, most likely addressing eccentric strength deficits, (Crosier et al., 2002) muscle-tendinous atrophy and scar tissue, (Artalejo et al., 1998) certainly changing the injury risk profile of the athlete with a previous hamstring strain, even when addressed after a significant time period following the initial injury and rehab. (Peterson et al., 2011)

Bold summary

"It is thus incontrovertible that the Nordic hamstring exercise program reduces hamstring injuries. It could almost be considered negligent not to provide eccentric hamstring strengthening in this form for athletes with a history of previous hamstring injury (i.e, athletes at high risk of re-injury)."

Related Articles

Evidence for the Late Swing

The Best Exercises Soccer Players Are Not Doing

Reducing ACL Injury Risk

Reference

Thorborg K. (2012) Why hamstring eccentrics are hamstring essentials. Br J Sports Med Vol 46:463-465

Artalejo FR, Banegas JR, Artalejo AR, et al. (1998) Number-needed-to-treat to prevent one death. Lancet  351:1365.

Askling C, Karlsson J, Thorstensson A. Hamstring injury occurrence in elite soccer players after preseason strength training with eccentric overload. Scand J Med Sci Sports 3:244–50.

Croisier JL, Forthomme B, Namurois MH, et al. (2002) Hamstring muscle strain recurrence and strength performance disorders. Am J Sports Med 30:199–203.

Grindstaff TL, Hammill RR, Tuzson AE, et al (2006). Neuromuscular control training programs and noncontact anterior cruciate ligament injury rates in female athletes: a numbers-needed-to-treat analysis. J Athl Train 41:450–6.

Petersen J, Thorborg K, Nielsen MB, et al. (2011). Preventive effect of eccentric training on acute hamstring injuries in men's soccer: a cluster-randomized controlled trial. Am J Sports Med 39:2296–303.

Silder A, Heiderscheit BC, Thelen DG, et al. MR observations of long-term musculotendon remodeling following a hamstring strain injury. Skeletal Radiol 37:1101–9.

Evidence for the Late Swing Phase

There is something about the biomechanics of running at high speed that increases the risk of a hamstring injury. This is something of a review, focusing on the late swing phase of the gait cycle with the intent that if we understand what is going on, we can structure our training programs better.

Better training = injury prevention/ reducing the risk of injury = better performance.

In keeping with the principles of training (specificity, progressive overload), programs would ideally incorporate aspects (e.g. postures, muscle lengths, contraction type) that are most similar to those conditions associated with injury. Only then would athletes optimize the gains in functional strength and minimize the risk of future injury.

THE STANCE PHASE:

Some researchers, however, propose that the hamstrings are most likely to be injured during the stance phase of the gait. This is mostly due to the the external loading on the limb that comes as a result of ground contact. Lateral and medial hamstrings and gluteus maximus showed similar activities with peak levels of EMG during foot-strike (Jonhagen S, et al., 1996).

Yu B, et al. (2008) included the following in their abstract: "The potential for hamstring muscle strain injury exists during the late stance phase as well as during the late swing phases of overground sprinting."

CAVEAT

Notwithstanding, a landmark article describing the work by Lieber and Friden (1993), though largely uncited, should be considered. It was entitled Muscle damage is not a function of muscle force but active muscle strain. (Journal of Applied Physiology. 1993;74:520–6.) They interpreted their findings to signify that "it is not high force per se that causes muscle damage after eccentric contraction but the magnitude of the active strain (i.e., strain during active lengthening)."

THE LATE SWING PHASE: FORM AND FUNCTION

Conceptually, hamstring lengths are primarily a function of the angles of flexion found at the hip and knees during running. For example, the hamstrings are lengthening during late swing when the hip is flexing and the knee is extending, as both of these motions contribute to hamstring stretch.

•  However, the hip starts to extend prior to foot contact and continues to extend throughout stance (47); 
• the knee flexes until mid-stance and then extends until toe-off. Therefore, if hamstring stretch is to occur during the second half of stance, the hamstring lengthening due to knee extension would have to exceed the hamstring shortening due to hip extension. 
• Further because the hamstring moment arms at the hip are greater than at the knee (13, 47), the knee extension velocity would have to exceed the hip extension velocity. 
• However, sagittal hip and knee angular velocities during stance tend to be of comparable magnitude (27), making it unlikely that substantial hamstring stretch is occurring during stance.

THE LATE SWING: STUDY EVIDENCE

Heiderscheit BC, et al. (2005) identified, based upon the earliest indications in marker trajectories, a 130 ms period during the late swing phase as the period of injury. The biceps femoris (BF) reached a peak musculotendon length up to 12% beyond the length seen in an upright posture and exceeded the normalized peak length of the medial hamstrings. "This case provides quantitative data suggesting that the biceps femoris muscle is susceptible to an lengthening contraction injury during the late swing phase of the running gait cycle."

In an interesting 2009 study, Schache A, et al. collected 10 normal sprinting trials for kinematic and GRF analysis, and compared them with one after a hamstring strain. "For the pre-injury trials, the right leg compared to the left displayed greater knee extension and hamstring muscle-tendon unit length during terminal swing, an increased vertical ground reaction force peak and loading rate, and an increased peak hip extensor torque and peak hip power generation during initial stance."

"For the injury trial, significant biomechanical reactions were evident in response to the right hamstring strain, most notably for the right leg during the proceeding swing phase after the onset of the injury. The earliest kinematic deviations in response to the injury were displayed by the trunk and pelvis during right mid-stance. Taking into account neuromuscular latencies and electromechanical delays, the stimulus for the injury must have occurred prior to right foot-strike during the swing phase of the sprinting cycle. It is concluded that hamstring strains during sprinting most likely occur during terminal swing as a consequence of an eccentric contraction." (Biomechanical response to hamstring muscle strain injury.)

Using 3-D videographic and EMG data from the maximal overground (as opposed to treadmill) sprinting efforts of 20 male runners, soccer and lacrosse players, Yu B, et al (2008) interpreted their findings as such; "The potential for hamstring muscle strain injury exists during the late stance phase as well as during the late swing phases of overground sprinting." (Hamstring muscle kinematics and activation during overground sprinting.)

OTHER POINTS TO CONSIDER

• Repetition: The biarticular hamstrings undergo maximal stretching during the late swing phase of running gait and also present with a repetitive active stretch-shortening contraction. "When active stretch-shortening cycles are imposed on a musculotendon unit, the degree of strain taken up by the fibers can change with time, making the muscle potentially more susceptible to injury after repeated loading cycles" (Butterfield and Herzog, 2005). Basically, the more strides you take, the greater the likelihood for injury. (Ever notice how nobody pulls up straight out of the blocks?)
• Negative work: When running at high speeds, the amount of negative/concentric work increases significantly and thus, the hamstrings may be susceptible to a late swing injury as a result of repetitive strides of high speed running. (Heiderscheit BC, et al., 2005 and Schache A, et al., 2009)
• Biceps Femoris Observations: BF loading increases with speed during swing but not stance. (Chumanov et. al., presently reviewed paper.)

It is worth noting that this information derives from studies and observations when the hamstrings are involved in forward sprinting at a fairly constant speed as in track sprinters. The hamstring loads that occur during sudden directional turns and accelerations as in soccer are vastly different, and could certainly factor into injury risk.

Hope Solo

Defining the musculotendon demands during sprinting, with specific emphasis on which time injury is most likely to occur offer direction as to the type of resistance training may be useful for injury risk management. The examples above suggest that the late swing is the time the hamstrings are most susceptible to injury. with this evidence, the most effective resistance training would be when the hip is in flexion and the knee in extension, as in the swing phase. For example, deadlifts, good mornings, back extensions.

Pauline Nordin

This data also provides evidence for the use of eccentric contractions under inertial load in programming. This approach has already been shown to be efficacious as a prevention and rehabilitative tool. See my article, "The Best Exercises Soccer Players Are Not Doing" , for an eccentric focused training program, including progressions from rehab to sport-specific training.

REFERENCES

All references in this article, unless otherwise stated refer to

Chumanov E. S, Heiderscheit B. C, and Thelen D. G (2011). Hamstring Musculotendon Dynamics during Stance and Swing Phases of High Speed Running. Med Sci Sports Exerc. 43(3): 525–532.

Strengthening Is Not The Same As Rehabilitation

There is a huge misconception floating in fitness centers all over the place- that injury is the result of weakness. "My back hurts; it must be weak." "I keep rolling my ankle. What can I do to make my ankles stronger?" 

Not every injury results from weakness. In fact, noted physiotherapist and strength coach Gray Cook and his team at Functional Movement Systems looked at the data before and since developing the FMS. The three leading causes for injury, they have found, are:

• Previous Injury
• Asymmetries 
• Motor control issues

CASE STUDIES

I met a young soccer player who had not played in a while, but was hoping to return to the game. He had stopped playing because of an ACL injury. He was not alone. I met two more athletes, promising, but also with fairly recent operations. One was a lacrosse player, the other had switched from baseball to slow pitch before hearing that dreaded "pop" sound. I talked to these guys individually, and even trained one of them for a couple of weeks. All three could be found on the leg press and leg extension machines when they came into. They all skipped the balance work they were given as homework by their physios. I tested them and was not surprised to find that they all scored poorly, even on the uninjured leg.

Rotation Movement That Causes ACL Injury

A regular gym-goer told me that his back and shoulder were hurting. "What do you think I should do?" He didn't seem like he would hang around long enough for me to get more information. I got his info, and since he had mentioned they only hurt when he did certain movements, I advised staying away from those movements and promised to send him a research paper that had some good information for back pain. I met the guy a week later.

"How's the pain," I asked. "Receded, I hope."

"It's not as painful now. I still have to do more strengthening work though," came the reply.

I mention this guy because its not just athletes who are in a hurry to get back to playing. Weekend warriors with gym memberships do this too. Think of the dads who 'come out of retirement' for their kid's Father-Son day game, or take part in a little sports day event.

The prevalent ignorance is not because people choose to be stupid. They just don't get it. They think they were weak to begin with, hence the injury. They think since they've had to sit out while recovering, their strength capacity is the only thing deconditioned.

A LITTLE SCIENCE

A medial knee position during the stance phase when running may affect the line of pull of the quadriceps and contribute to the etiology or exacerbation of overuse injuries such as patellofemoral pain.

Stefanyshyn et al., (2006) hypothesized that increased internal hip and knee abduction moment during running results in greater forces on the lateral facet of the patella. These faulty/altered biomechanics likely result in increased contributions from the vastus lateralis, extensions of the iliotibial band, or both. Greater force on the patella from these tissues may result in greater retropatellar stress and activation of nociceptive fibers in patellar subchondral bone or synovium. They concluded that increased knee abduction impulses should be deemed risk factors that play a role in the development of patellofemoral pain in runners.

THE EVIDENCE

One of the main culprits when athletes have altered mechanics is the hip. Studies have been conducted assessing the effectiveness of strengthening the joint in these situations. In one, females with patellofemoral pain (PFP) demonstrated significantly less peak hip adduction while running at the end of a 2‐week training program when they were given visual 3-D feedback of what the hip was actually doing while they ran. (Noehren B, Scholz J, Davis I., 2011). In another, a study including a 14‐week rehabilitation ‐program for PFP that also included visual feedback and hip strengthening exercises was also found to decrease pain and hip adduction angle during a single leg step down. (Mascal C, Landel R, Powers C., 2003). Finally, in a study by (Herman D, Oñate J, Padua D, et al., (2009) peak hip adduction and knee abduction angles during a drop jump activity decreased among subjects who received visual feedback for altering movement performance and strength training. Most importantly, subjects who received the strength training intervention alone did not experience these changes.


Decreases of 15% in internal hip abduction and a 23% knee abductor moments were reported by Earl et al following an 8‐week “proximal stability program” that included five weeks of training including attention to lower extremity alignment during exercises for patellofemoral pain.

Wouters, et al., (2012) found internal hip and knee abduction moments decreased by 23% and 29%, respectively. They also found that subjects demonstrated less knee abduction excursion and increased knee adduction excursion during the stance phase of running after the movement training program.

The relevance of these studies is that hip strengthening alone may not be an effective remedy for altered lower extremity running mechanics that may increase the risk of running related injury. Based on the available evidence, it seems programs should emphasize neuromuscular control ‐elements such as guided practice of movement performance and visual, verbal, and tactile feedback rather than hip strengthening alone.

Motor control, stability, mobility. These three things are very important. We can't see them when they're there but we are immediately drawn to them when they are absent. How often have we seen players walk off the field only to hear that they picked up a knock and were substituted at half time? I'm writing this because I'm hoping the thing that draws us to the absence of those three factors is injury. If it is, hopefully we won't skip over them in favor of speed work, some weights and plyometrics.

There ought to be a progressive approach to returning to play. Address mobility. Soccer players are notorious for skipping the warm up. Or they have one, but it is ridiculous. Why is it that the numbers reflecting non-contact ACL injuries continues to increase when FIFA has had a prevention program out for years?...

Related Articles

Mechanisms of Non-contact ACL Injury

F-MARC's 11+ Warm-up Program

Reference

Wouters, I., Almonroeder, T., DeJarlais, B., Laack, A., Willson, D. and Kernozek, TW. (2012). Effects of A Movement Training Program On Hip and Knee Joint Frontal Plane Running. Int J Sports Phys Ther. 7(6): 637–646.

The Best Exercises Soccer Players Are Not Doing

As players fatigue, it is not difficult to imagine that they are more susceptible to injury. It is not just a matter of concentration. There are measurable physiological changes that should inform every coach's conditioning program. Conditioning should be more than just running around the field at the start of practice, or worse, punishment for losing the last game. By addressing these changes, coaches can both prevent injury and enhance performance, particularly in the latter stages of a game. In this article, I review several studies which purport to do just that.

INJURY PREVENTION

Askling and others considered the relationship between 10 weeks of eccentric training and subsequent injury in elite players. Thirty players were divided into two groups with one adding the training 1-2 times a week to their regular training. The group that performed just their regular team training served as the control group. Injuries were monitored over 10 months after the training intervention. The eccentric training group had significantly fewer hamstring injuries (3/15) compared to the control group (10/15).

The Nordic hamstring exercise was one of three interventions that Arnason et al., used to investigate the incidence and severity of hamstring strain. Participants, who were professional soccer players, performed as methods of comparison (1) warm up stretching performed independently with contract-relax stretching and (2) partner-assisted contract-relax hamstring flexibility exercises. The overall incidence of hamstring strains was 65% lower in the eccentric group (injury severity and re-injury rates were not statistically significantly different.)

In a separate study, Brooks et al., examined the effects of eccentric hamstring lowers and stretching on the incidence and severity of hamstring strains in 546 professional rugby players. The intervention group was reported to display significantly lower incidence and severity of hamstring injury than the strengthening group and the conventional stretching/strengthening group.

Nordic Hamstring Exercise

PERFORMANCE IMPROVEMENT MEANS

CONDITIONING AT THE RIGHT TIME...

Small et al, investigated, over 8 weeks, the effect of eccentric hamstring strengthening during soccer training, their capacity to tire (fatigability) and whether eccentric training has any effect on this. They commissioned sixteen semi-professional players who completed a 90-minute simulated soccer game. Isokinetic testing on the hamstrings and quadriceps was performed during half time and at the end. The subjects were divided into two groups, both performing the “Nordic hamstring” eccentric exercise twice weekly for the entirety of the study. One group performed the exercise during the warm-up, and the other during the cool-down. This latter group that had the better results as far as the study was concerned. They "showed significant increases in eccentric hamstring peak torque and the functional eccentric hamstring to concentric quadriceps ratio post-intervention compared to the warm-up group." The investigators concluded that eccentric strength training performed post-training reduced the effects of fatigue, but the beneficial effects are time-dependent. (Interestingly, FIFA's 11+ program has the Nordic hamstrings exercise as part of the warm-up.)

Clark et al., found that after four weeks of training with the Nordic hamstring exercise, vertical jump and peak torque of the hamstrings increased.

In the study by Askling et al., that I mentioned before, the investigators checked strength and speed as well. The eccentric training group showed statistically significant improvements in strength and speed.

... IN THE RIGHT WAY

Training the hamstrings, like training any other component, should not be a haphazard thing. It must follow the principle of progressive overload. Comfort et al., in agreement developed a continuum addressing rehabilitation needs for the injured athlete up to sport specific work for those targeting improved performance. It follows the 3-phase approach to hamstring rehabilitation after injury. After the first phase, they suggest low-velocity eccentric activities such as

• stiff leg dead lifts,
• Nordic hamstring exercise, and
• split squats. 
• in split-stance deadlift (“good morning” exercise) with the load in front of the body, as opposed to a posterior load utilized during the traditional performance of this exercise. The subject then leans forward through flexion ...
• single and double leg deadlifts,
• eccentric lunge drops (Begin in a split stance position and drops rapidly into a lunge position.)

The next phase involves higher velocity eccentric exercises designed to increase hamstring torque and lower extremity power:

• squat jumps,
• split jumps, 
• bounding,
• depth jumps
• box jumps.

Split Jumps (Men`s Health)

Finally, sport specific progressions should complete the program.

Note: The italicized exercises were not listed in the program suggested by Comfort et al. Instead, they were from a separate discussion of conditioning the hamstring both for rehabilitation, injury prevention and performance enhancement by Brughelli and Cronin. I thought that they would fit particularly well as I try to provide a variety of exercises.

Comfort et al., also suggest a directional overload within their continuum. Progress from unidirectional linear movements to bidirectional and then multi-directional movements. Some of these exercises may include

• single leg bounding, 
• backward skips, 
• lateral hops, 
• lateral bounding,
• zigzag hops and bounding. 

Once multi-directional closed and open chain exercises are tolerated, the next step is to address stride length and stride frequency. The former can be affected by running uphill while the latter can be improved by running downhill. Downhill running will also help the athlete get used to shifting between concentric and eccentric movements.

                                         

REFERENCES


Daniel Lorenz, D., Reiman, M. (2011). The Role and Implementation of Eccentric Training in Athletic Rehabilitation: Tendinopathy, Hamstring Strains, and ACL Rconstruction. The International Journal of Sports Physical Therapy. Volume 6, Number 1, Page 27


Greig, M and Siegler, JC. (2009). Soccer-Specific Fatigue and Eccentric Hamstrings Muscle Strength. Journal of Athletic Training. Volume 44, Number 2, Pages 180–184

Why Is Screening So Important?

Why is screening so important? Screening is information gathering, nothing else. The season is a journey and in order to get there both safely, and as quickly as possible, you are going to need a road map. The screen basically tells you where you are now, and helps plan the way to get to there. No doubt, that is a winner's medal around your neck at the end of the season. Or the Ballon d'Or if you are Lionel Messi.

When you have won it 4 times, you can wear Polka dot too.

I am a big of the functional movement screen. It works. In a matter of minutes, issues of mobility and stability (or the lack thereof) can be identified. I remember in 2008, when I was still in South Africa, my best friend and out went out to meet Platinum Stars FC. I was in my last year as a candidate for a Bachelor's degree in Human Movement Science. One of our courses was Exercise Testing and Prescription and we were going to put theory into practice. Following the directions from our instructor, we split the Stars into groups and got to work.

We took them through the 10 stations we had set up. The anthropometric measures were taken over 3 stations before going through the 7 of the FMS. It was not very difficult. Zahraa and I just held the clipboards and recorded the scores that our instructor called out. It took a while though. Not only was it very cold, but when it came to getting skinfold measures and such, the players were hesitant to hang out with their shirts off while two students made marks in their skin with pens. We didn't always get the c-grip right, so the calipers pinched. A lot. It was also preseason stuff, and it seemed some of the players had had a few too many pies during their time off. Did I mention it was cold? 

"2. Stiff ankles. Needs more mobility there...."

"Tight shoulders. Give him a 1."

"No glutes. A 1."

Zac rattled off these things all day, and every now and then I got a chance to see what he was talking about. At some point, I blurted out, "How do you know?" He just answered I'll show you tomorrow.

Tomorrow finally came, and I made sure Zac kept his promise. After setting up the light gates, the players went through them a number of times. We measured time to get through the distance, and factored that into acceleration calculations. We watched them sprint and considered how easily they turn with one foot compared to the other. The T-test for agility followed. As the day continued, Zac explained himself and I could see the correlation between the movement screen ratings and the performance scores.

The same players that had ankle mobility issue had average performances when it came to the agility tests. One guy kept rolling both his ankles. The same players who had tight shoulders were very stiff in their posture as they ran. I found out about a few players who had been struggling with groin injuries. Their Active Straight Leg Raise Scores were not very pleasing, saying nothing of the other tests that require contribution from the core. Read this article to find out How a good core can benefit your game.

The fundamentals of mobility and stability form the foundation upon which strength, speed, power, agility and all the other elements of performance we work for are built. Ignoring them is counterproductive. Screening is helpful for identifying players who are at risk for injury, and hence equip coaches and trainers to design programs to get those players out of risk. Those out of risk, programs can be designed to challenge them to the next level. After all, the 11+ players on the team are 11+ individuals. Should they not be trained as individuals?

The exceptional Hope Solo. (Image from si.com)

Why Soccer Players Need Abs

THE PROBLEM

A good set of abs isn't just pleasing on the eye, it has a functional purpose. That is no guarantee is that everyone will be a star like those pictured here. But for the purposes of injury prevention and improving performance, they are a worthy investment. The problem is, with tactics and techniques to address, as coaches, we just don't have the time for core work at a practice session. And if yours is not a professional club, you don't have days for fitness training set aside, leaving a few laps or suicides (or God forbid laps around the field) to be squeezed in during an already insufficient hour or two. 

THE SOLUTION

As a personal trainer, one of the more frustrating (for the entire profession really) issues, is that I only have one hour a day to educate my clients. But until those things we discuss become a habit, the remaining 23 hours are spent undoing the work of that one hour. Diet, posture and other habits. My success lies in adopting a relationship with my clients that allows me to be influential even outside of the gym. That means via e-mail, text and any other way I can, I have to encourage them to adopt those behaviors that will be in line with the work in that one hour. As a coach then, the same approach will ensure your limited time with the players will not be undone by their everyday goings-on.

THE SCIENCE

Most soccer players favor one foot over the other. Even after years of practice, I am far more accurate with more right foot than I am with my left. The same holds true for the speed and power I can produce with either foot. This preference induces imbalances and asymmetries which predispose players to injuries. These include muscle strength imbalances and side-to-side differences in the cross-sectional area (CSA) of lower limb and trunk muscles. Balancing ability between the left and right sides also differs.

The muscles of the abdominal wall contribute to stabilizing the trunk. Rectus abdominis (RA) in particular, maintains balance during stop-start activities, rapid changes of directions or contacts with other players. It is also submitted to very high loads when kicking, being responsible for the powerful flexion and rotation of the trunk in the direction of the non-dominant side.

                                                 

In regions closest to the pubic symphysis, the rectus abdominis muscle shows greater volume on the dominant when compared to the non-dominant side, reflecting greater stretch-shortening loads during kicking. It is these fast stretch-shortening cycles that allow trunk rotation and flexion to apply maximal power to the ball. This increase in size could contribute to the increase in the force generating capacity and peak power of the dominant-leg. This function suggests that players wishing to increase force production during kicking could benefit from rectus abdominis hypertrophy.



The side-to-side differences in the rectus abdominis muscle have, however, been associated with chronic groin pain and low back pain. In the literature, it remains to be seen whether training that addresses the asymmetry can contribute to reducing the the risk of this pain in soccer players specifically. Players will benefit from any training that targets symmetry and balance though. As Gray Cook and co have shown, (I highly recommend the books Athletic Body In Balance and Movement) symmetry and balance not only reduce the risk of injury but provide a foundation for better performance.

THE HOW

Two of the best minds that have influence my thinking when it comes to training have addressed core work more than effectively. In order to do them justice, and to make sure you are coached by the very best, check out the link and videos below.

First, a demonstration and explanation of the the most effective plank I have ever tried by Bret Contreras.

Gray Cook does a fantastic job (who else!) of teaching the chop and lift which will address side to side differences, ab strength and eventually power. (Lengthy but worth it!) 

• In this video, he explains and teaches mountain climbers. Perform these with all the cues he provides before adding the resistance bands. 

The mountain climbers and the chop and lift will do wonders to address the side to side imbalances I talked about. They will need to be a regular part of training. The plank will challenge the core as a whole, in a sense integrating the new found strength. At the end of the day though, nothing builds abs like sprinting. Strong shoulders drive the body diagonally, achieving oblique engagement better than any exercise we can prescribe in the gym. You will find that athletes will be better sprinters when they have a better functioning core.

So what are the benefits of Abs for the soccer player?

• Better sprinting
• More powerful shooting
• Reduced injury risk (groin, lower back, etc) and of course,
• They look good!

Reference

Idoate, F., Calbet, J. A. L., Mikel Izquierdo, M., and Sanchis-Moysi, J. (2011). Soccer Attenuates the Asymmetry of Rectus Abdominis Muscle Observed in Non-Athletes. PLoS One. 6(4)

Reducing ACL Injury Risk

In my first summary of a pair of excellent review studies addressing non-contact ACL injuries, I listed the modifiable factors. Review that article here. This article summarizes how and why training can reduce the risk of injury.

You can also access the full review studies here and here. (References in parentheses refer to these articles)

KEY POINT

"The implementation of interventions that incorporate core stability training, including proprioceptive exercise, perturbation, and correction of body sway, has the potential to reduce knee, ligament, and non-contact ACL injury risk in both female and male athletes [79]." By contrast, "continued performance in the presence of faulty technique increases the likelihood of the athlete’s sustaining a training induced knee injury." [56]

It seems that non-contact ACL injuries can be brought down to posture at landing or during movements. Most of the athletes (if not all) who would fall into the the at-risk category are not aware of it. A good start for reducing risk would be education- teach them what it is that is putting them at risk so that they are aware. Consequently, athletes will work with trainers and coaches in their efforts towards "technique modification, proprioception training, and plyometric training [as this] is essential to evoke changes in kinematics and kinetics of joints during sports tasks."

The conundrum of training is that some of the components that will be mentioned here as measures of training effectively, and thereby reducing the risk of injury, are age specific. Young players learn to kick, throw and jump as is appropriate for their level. As they mature physically, training/coaching generally only "matures" in that the intensity is increased- kick further, jump higher, run faster. This is not surprising at all as there is a natural shift from the fun in learning the fundamentals to more results driven competition. Feedback in practice is concerned with tactics, rather than technique; positional play, when it is incumbent upon coaches and trainers to realize that there are fundamentals at every level. But, thus driven, the window at which training technique would be most effective both for performance and injury risk reduction may be passed by. A recent article was published suggesting that "ACL injury risk can be reduced by 72% in players who begin an injury prevention program during their early and mid-teenage years."

STRENGTH TRAINING FOR MUSCLE WEAKNESS

The injury prevention/performance enhancing benefits of strength training do not lie in the strength of the muscle. Instead, they lie in the muscle's ability to activate and react in time and in sequence with the other muscles involved in a movement. Consider the hamstrings.

Hamstrings have an important role in protecting the ACL by preventing or decreasing the anterior, varus-valgus, and rotatory displacement of the tibia on the femur. Hamstring recruitment reduces the load imposed on the ACL from the more powerful quadriceps [155, 185], and by resisting anterior and lateral tibial translation and transverse tibial rotations, may help to provide dynamic knee stability [104].

Strength training is the obvious solution to cases of muscle weakness. Overall, training aimed to improve hamstring-to-quadriceps, hip, and trunk muscular strength is considered adequate to reduce the risk of non-contact ACL injuries. Eccentric loading of the hamstrings was shown, in various studies, to be more effective in increasing hamstring-to-quadriceps strength ratios than traditional concentric exercises in professional and semi-professional male soccer players.

STRENGTH TRAINING FOR ALIGNMENT AND JOINT STABILITY

Dynamic joint stability is provided by muscles as well as the elastic components of the musculotendinous unit, the sensorial and neural system. Single-component preventive programs have limited impact on biomechanical risk factors, as they may be too focused on the muscle component thereby minimizing potential improvements in other important components of the dynamic joint stability function.

Because muscle actions must be coordinated and co-activated in order to protect the knee joint [185], antagonist–agonist relationships are crucial for joint stability. Hence, preseason and continued in-season conditioning focused on hamstring strengthening is indicated. Research also shows that "coactivation of gluteus maximus and medius and hip joint position are essential elements to provide a safe biomechanical profile." Further, "relative weakness of the abductors, extensors, and external rotators, compared to the flexors and adductors, coupled with increased hip flexion , may severely limit the ability of the gluteal muscles to stabilize the hip and maintain a neutral alignment of the hip and knee [69]."

Both joint stability and muscle co-activation were adequately addressed following plyometric training. "The plyometric component of preventive programs trains the muscles, connective tissue, and nervous system to effectively carry out the stretch-shortening cycle and focuses on proper technique and body mechanics [29]. Following training, a significant increase in firing of adductor muscles during the preparatory phase was noted. A significant increase in preparatory adductor-to-abductor muscle co-activation was identified, as well as a trend toward reactive quadriceps-to-hamstring muscle co-activation."

LANDING

Landing presents a load of several time the athlete's body weight on the knee. Typically its the "extended hip and knee joint posture upon landing" that poses a risk. Coaches need to teach their athletes to land softly, "with initial contact at the forefoot with hip and knee flexion with knees over the toes." Also, it was shown that increased trunk flexion during landing avoided excessive anterior translation. This is a more desirable landing technique in order to reduce the risk of non-contact ACL injuries [32, 65]- land on the balls of their feet and sink into the ground, bending knees and hip, as in a squat.

EXPECT THE UNEXPECTED

Cutting maneuvers performed in response to changes in the direction of play, or a dribble constitute a particularly high risk position in soccer. This is mainly because players have so little time to respond if they want to keep up. The results are unplanned movements, unaccompanied by the small steps and other changes in posture which ordinarily decrease the external varus/valgus and internal/ external rotation moments applied to the knee. Warned, players can prepare better and it is therefore advisable to add components of visual cue interpretation to increase the time available for pre-planned movement.

In support, Nyland et al. support programs that focused on coordinated lower extremity closed kinetic chain tasks-

• mini-squats, 
• single-leg vertical and horizontal hopping,
• lateral shuffles in a mini-squat position,
• back pedaling, and 
• quick multidirectional movement responses to cues [56]. They recommended that these tasks should be performed progressively and with an emphasis on movement quality.

Besier et al. further recommended that training should involve drills that familiarize players with making unanticipated directional changes. Applying all reason and precautions for safety, practice should mimic as much as possible the game situation, particularly in speed and tempo. Drills are often slow so that even if players are familiar with certain movements, it is the added speed and perturbations that predispose them to injury during matches.

Applying these will go a long way in decreasing the risk of injury and improving performance as well.