Applied Sports Science newsletter – November 1, 2016

Los Angeles Lakers general manager Mitch Kupchak recently spotted something unusual while watching forward Julius Randle working out on the court. He wouldn’t quite elaborate on what he saw, only saying that Randle was working on a few moves that seemed new, but it made Kupchak curious.

“Julius, why don’t you do that more often?” Kupchak asked.

Randle pointed to his right leg, the one he broke in the team’s season-opener against the Houston Rockets two years ago, sidelining him for his entire rookie campaign after being drafted seventh overall in the summer of 2014.

“I’m just getting complete confidence now,” Randle told Kupchak.

… In addition to Dembélé, a host of bright young things — the Turkish wing Emre Mor, 19; the Spanish midfielder Mikel Merino, 20; the versatile Portuguese Raphaël Guerreiro, 22 — would arrive at Dortmund’s Signal Iduna Park, along with a contingent of more experienced faces like the German internationals André Schürrle and Mario Götze.

One by one, each arrival eased the sting of what could have been a dispiriting summer for Dortmund, Germany’s second superpower. Bayern Munich, as it seems to do every year, had plucked one of Dortmund’s crown jewels, the captain Mats Hummels, and the core midfielders Henrikh Mkhitaryan and Ilkay Gundogan soon followed him out the door, bound for the Premier League.

“We gave long consideration on how to replace the players we lost,” Michael Zorc, Dortmund’s technical director, said. “We decided to go with a two-column model: very young, highly skilled players, but also established, internationally experienced ones.”

The result is, arguably, the most gifted collection of young players anywhere in Europe, crafted into a team of rich spirit and endless adventure by Thomas Tuchel,

THE MEN WHO agree to talk about what happened do so reluctantly. Their eyes invariably drift to the spot in question: the grass practice field, somewhere near the 30-yard line, right hash. It happened with the offense heading north, 22 men on the field, no contact allowed.

They won’t talk about what the injury looked like, out of respect. These are men who long ago came to terms with the inhumanity of their game. They laugh about concussions and broken bones as a defense mechanism, the way an electrician might laugh with his buddies about getting a jolt from a faulty circuit. Occupational hazard.

But this is different. They close their eyes and wince, the image flashing in their minds. They shake their heads reflexively, as if they can dislodge the memory and evict it from their brains. They watched Teddy Bridgewater go down on that field on Aug. 30, his left leg separating at the knee, during the first minutes of a Vikings preseason practice. Every time they think about it, every time they stand near this field and close their eyes, they see it again.

Aims (1) To investigate whether a daily acute:chronic workload ratio informs injury risk in Australian football players; (2) to identify which combination of workload variable, acute and chronic time window best explains injury likelihood.

Methods Workload and injury data were collected from 53 athletes over 2 seasons in a professional Australian football club. Acute:chronic workload ratios were calculated daily for each athlete, and modelled against non-contact injury likelihood using a quadratic relationship. 6 workload variables, 8 acute time windows (2–9 days) and 7 chronic time windows (14–35 days) were considered (336 combinations). Each parameter combination was compared for injury likelihood fit (using R2).

Results The ratio of moderate speed running workload (18–24 km/h) in the previous 3 days (acute time window) compared with the previous 21 days (chronic time window) best explained the injury likelihood in matches (R2=0.79) and in the immediate 2 or 5 days following matches (R2=0.76–0.82). The 3:21 acute:chronic workload ratio discriminated between high-risk and low-risk athletes (relative risk=1.98–2.43). Using the previous 6 days to calculate the acute workload time window yielded similar results. The choice of acute time window significantly influenced model performance and appeared to reflect the competition and training schedule.

Conclusions Daily workload ratios can inform injury risk in Australian football. Clinicians and conditioning coaches should consider the sport-specific schedule of competition and training when choosing acute and chronic time windows. For Australian football, the ratio of moderate speed running in a 3-day or 6-day acute time window and a 21-day chronic time window best explained injury risk. [full text]

The trainability of youths and the existence of periods of accelerated adaptation to training have become key subjects of debate in exercise science. The purpose of this meta-analysis was to characterise youth athletes’ adaptability to sprint training across PRE-, MID-, and POST-peak height velocity (PHV) groups. Effect sizes were calculated as a measure of straight-line sprinting performance with studies qualifying based on the following criteria: (a) healthy male athletes who were engaged in organised sports; (b) groups of participants with a mean age between 10 and 18 years; (c) sprint training intervention duration between 4 and 16 weeks. Standardised mean differences showed sprint training to be moderately effective (Effect size=1.01, 95% confidence interval: 0.43-1.59) with adaptive responses being of large and moderate magnitude in the POST- (ES=1.39; 0.32-2.46) and MID- (ES=1.15; 0.40-1.9) PHV groups respectively. A negative effect size was found in the PRE group (ES=-0.18; -1.35-0.99). Youth training practitioners should prescribe sprint training modalities based on biological maturation status. Twice weekly training sessions should comprise up to 16 sprints of around 20 m with a work-to-rest ratio of 1:25 or greater than 90 s.

… the notion that City would have been able even to compete with a club of Barça’s heritage and resources in the increasingly ferocious battleground of elite youth football would have been considered ludicrous just a decade ago. To trace the roots of City’s rise, you must travel four stops on the Metrolink tram from Manchester Piccadilly and alight at Velopark. Opposite lies the City Football Academy, which had cost the club’s Abu Dhabi owners a princely £150 million when it opened in 2014.

During exercise, there is a progressive reduction in the ability to produce muscle force. Processes within the nervous system as well as within the muscles contribute to this fatigue. In addition to impaired function of the motor system, sensations associated with fatigue and impairment of homeostasis can contribute to the impairment of performance during exercise. This review discusses some of the neural changes that accompany exercise and the development of fatigue. The role of brain monoaminergic neurotransmitter systems in whole-body endurance performance is discussed, particularly with regard to exercise in hot environments. Next, fatigue-related alterations in the neuromuscular pathway are discussed in terms of changes in motor unit firing, motoneuron excitability, and motor cortical excitability. These changes have mostly been investigated during single-limb isometric contractions. Finally, the small-diameter muscle afferents that increase firing with exercise and fatigue are discussed. These afferents have roles in cardiovascular and respiratory responses to exercise, and in the impairment of exercise performance through interaction with the motor pathway, as well as in providing sensations of muscle discomfort. Thus, changes at all levels of the nervous system, including the brain, spinal cord, motor output, sensory input, and autonomic function, occur during exercise and fatigue. The mix of influences and the importance of their contribution vary with the type of exercise being performed.

This study investigated the influence of repeated high-intensity effort exercise on tackling ability in rugby league players, and determined the relationship between physical qualities and tackling ability under fatigued conditions in these athletes. Eleven semi-professional rugby league players underwent measurements of speed (10 m and 40 m sprint), upper-body strength (4 repetition maximum [RM] bench press and weighted chin-up), upper-body muscular endurance (body mass maximum repetition chin-up, body mass maximum repetition dips), lower-body strength (4RM squat), and estimated maximal aerobic power (multi-stage fitness test). Tackling ability was assessed using a standardized one-on-one tackling test, before, during, and following four bouts of repeated high-intensity effort (RHIE) exercise. The relationship between physical qualities and fatigue-induced decrements in tackling ability were determined using Pearson product moment correlation coefficients. Each cycle of the RHIE protocol induced progressive reductions in tackling ability. A moderate reduction (Effect Size = ~-1.17 ± 0.60, -34.1 ± 24.3%) in tackling ability occurred after the fourth cycle of the RHIE protocol. Players with greater relative lower-body strength (i.e. 4RM squat/kg) had the best tackling ability under fatigued conditions (r = 0.72, p = 0.013). There were no significant relationships between tackling ability under fatigued conditions and any other physical quality. These findings suggest that lower-body strength protects against fatigue-induced decrements in tackling ability. The development of lower-body strength should be a priority to facilitate the development of robust tackling skills that are maintained under fatigue. [full text]

The V˙O2 slow component (V˙O2sc) that develops during high-intensity aerobic exercise is thought to be strongly associated with locomotor muscle fatigue. We sought to experimentally test this hypothesis by pre-fatiguing the locomotor muscles used during subsequent high-intensity cycling exercise. Over two separate visits, eight healthy male participants were asked to either perform a non-metabolically stressful 100 intermittent drop-jumps protocol (pre-fatigue condition) or rest for 33 min (control condition) according to a random and counterbalanced order. Locomotor muscle fatigue was quantified with 6-s maximal sprints at a fixed pedaling cadence of 90 rev·min−1. Oxygen kinetics and other responses (heart rate, capillary blood lactate concentration and rating of perceived exertion, RPE) were measured during two subsequent bouts of 6 min cycling exercise at 50% of the delta between the lactate threshold and V˙O2max determined during a preliminary incremental exercise test. All tests were performed on the same cycle ergometer. Despite significant locomotor muscle fatigue (P = 0.03), the V˙O2sc was not significantly different between the pre-fatigue (464 ± 301 mL·min−1) and the control (556 ± 223 mL·min−1) condition (P = 0.50). Blood lactate response was not significantly different between conditions (P = 0.48) but RPE was significantly higher following the pre-fatiguing exercise protocol compared with the control condition (P < 0.01) suggesting higher muscle recruitment. These results demonstrate experimentally that locomotor muscle fatigue does not significantly alter the V˙O2 kinetic response to high intensity aerobic exercise, and challenge the hypothesis that the V˙O2sc is strongly associated with locomotor muscle fatigue. [full text]

Think about the subjects that crop up most in those nerdy running chats with your friends. Speed endurance, V02 max, running economy and lactate threshold will be in there. And so they should; they all come into play as you work to become a stronger runner. But how often do you mention your bones?

Taking care of your skeleton is every bit as vital as warming up, cooling down, protein drinks, compression and everything else you do to try to improve performance and avoid the physio. When you think about it, it’s obvious: your bone structure is, after all, what’s holding you up. And yet this vital part of our body is often abused with impunity, and with dire consequences: just one form of bone-related injury, medial tibial stress (shin-bone stress) accounts for 10-15 per cent of running injuries, and research from Louisiana State University School of Medicine, US, found the recovery time for a stress fracture to be anything from four weeks to three months.

So why aren’t we runners better at taking care of our bones? Partly because, until recently, the vast majority of research done on bone health had been carried out on older, less active groups, focusing on age-related problems such as osteoporosis. But now the amount of research in young, healthy, active people has started to grow.

… in Barça’s first-ever public presentation in Silicon Valley earlier this month, Raúl Peláez, the club’s head of sports technology, explained how Barça uses tech to help its athletes reach their full potential. … Responsible for all areas of Barça’s technology that relate to athletes and coaches, Peláez said his job is to “put all its players in a position to win,” and that includes a wide variety of existing and emerging technologies.

I wrote a blog recently called When can I return to sport after ACL surgery?. It summarised two recent articles by Grindem et al (2016) and Krytsis et al (2016) that both clearly showed a reduction in ACL re-injury risk in elite adult athletes who waited at least 9 months, and passed a battery of strength and functional tests prior to being cleared to return to sport (RTS). To reiterate the above literature; waiting at least 9 months, being within 10% of the uninjured limb on a number of different strength and hop tasks, performing an agility T-test under 11 seconds and performing sport-specific conditioning at training, significantly reduced the athlete’s risk of re-injuring their ACL upon RTS.

This blog however will be a little different as I wanted to explore some worrying trends in the literature that suggest we should be more conservative with our RTS planning in our younger athletes who have had ACL reconstructive surgery – specifically those athletes under the age of 20.

PURPOSE:

There is a lack of consensus regarding the appropriate criteria for releasing patients to return to sports (RTS) after anterior cruciate ligament reconstruction (ACLR). A test battery was developed to support decision-making.
METHODS:

Twenty-eight patients (22 males and 6 females) with a mean age of 25.4 ± 8.2 years participated and were 6.5 ± 1.0 months post-ACLR. All patients followed the same rehabilitation protocol. The test battery used consisted of the following: isokinetic test, 3 hop tests and the jump-landing task assessed with the LESS. The isokinetic tests and single-leg hop tests were expressed as a LSI (involved limb/uninvolved limb × 100 %). In addition, patients filled out the IKDC and ACL-Return to Sport after Injury (ACL-RSI) scale. RTS criteria to pass were defined as a LSI > 90 % on isokinetic and hop tests, LESS 56 and a IKDC within 15th percentile of healthy subjects.
RESULTS:

Two out of 28 patients passed all criteria of the test protocol. The pass criterion for the LESS 90 % for SLH, 85.7 % for TLH and 50 % for the SH. For the isokinetic test, 39.3 % of patients passed criteria for LSI peak torque quadriceps at 60°/s, 46.4 % at 180°/s and 42.9 at 300°/s. In total, 35.7 % of the patients passed criterion for the peak torque at 60°/s normalized to BW (>3.0 Nm) for the involved limb. The H/Q ratio at 300°/s > 55 % for females was achieved by 4 out of 6 female patients, and the >62.5 % criterion for males was achieved by 75 %. At 6 months post-ACLR, 85.7 % of the patients passed the IKDC score and 75 % the ACL-RSI score >56 criteria.
CONCLUSION:

The evidence emerging from this study suggests that the majority of patients who are 6 months after ACLR require additional rehabilitation to pass RTS criteria. The RTS battery described in this study may serve as a framework for future studies to implement multivariate models in order to optimize the decision-making regarding RTS after ACLR with the aim to reduce incidence of second ACL injuries.

It’s probably happened to you. Deep into a long training day you start craving a bacon cheeseburger and suddenly that pile of ground meat is all you can think about. Turns out, you’re not alone. Even the best athletes lust after certain foods during a race or run. Here are a few of the things athletes crave, plus a biological explanation of why these cravings happen.

From eight glasses of water a day to protein shakes, we’re bombarded with messages about we should drink and when, especially during exercise. But these drinking dogmas are relatively new. For example, in the 1970s, marathon runners were discouraged from drinking fluids for fear that it would slow them down.

Now we’re obsessed with staying hydrated when we exercise, not just with water but with specialist drinks that claim to do a better job of preventing dehydration and even improve athletic performance. Yet the evidence for these drinks’ benefits is actually quite limited. They might even be bad for your health in some instances. So how did sports drinks come to be seen as so important?