Sports Science Monthly – March 2021

Every month we take a deep dive into the latest research in sports science. This month’s topic lines up with the March site theme on HMMR Media: sprinting. We have some new research on why sprint times slow with age, hamstring exercises for sprinting, and sex-specific injuries in running. In addition we also review some new research on sleep, predicting performance, and much more.

As always, the full Sports Science Monthly is available exclusively to HMMR Plus Members. You can browse the past topics on our archive page. The first topic below is free to everyone, but sign up now to read about all the latest research. To get an idea of what Sports Science Monthly is all about, the April 2016 edition is available in its entirety for free.

This Month’s Topics

Why do sprinters slow with age?

Quick Summary – Sprinters get slower with age; if we want to maintain sprinting performance for as long as possible, understanding why this slowing occurs is important. This paper suggests the main reasons are a loss of fast-twitch muscle fibers, general coordination ability, and potentially the accumulation of neuromuscular damage over time.

At the start of the year, I got a welcome New Year’s gift; a paper I had authored with John Kiely and Dylan Hicks was published in the Journal of Ageing and Physical Activity. The paper is an exploration of why masters sprinters are slower than younger sprinters, and contains a host of practical insights that may prove useful for those programming sprint training for older athletes. Whilst the paper is paywalled, if you contact me via ResearchGate, I’d be more than happy to send you a copy for free.

If we look at the age-group 100-meter world records for both male and female athletes, we see a general trend of reduced performance with increasing age. In the men’s event, the overall World Record of 9.58s (from Usain Bolt) compares to 9.87s (Justin Gatlin) in the M35 category, 10.72 (Willie Gault) in the M45 category, and 12.31 (Leake) in the M65 age group. This general reduction in performance then accelerates; the M85 World Record is 15.08s; the M90 record is 17.53s, and the M95 is 20.41s. A similar trend is seen in females; the overall World Record is 10.49 (Flo-Jo); Merlene Ottey has the W35 – W50 records (going from 10.74 to 11.67s), and the W65 record is 13.91s. Again, the older the age category in women, the more rapid the decline; the W80 record is 16.81s; the W85 19.37s, and the W90 is 23.15s.

Interestingly, there is something of a “reverse relative age effect” in play here; unlike in junior sports, where the relatively older athletes (in terms of birth month) tend to have more success, in masters sprinting it appears that the relatively younger athletes in each age category tend to perform best. The overwhelming trend for age-category World Records in masters sprinting is for athletes in the first year of that age group—i.e. the youngest—are the record holders. The questions we sought to answer in this paper were: a) why are elite masters sprinters slower than their younger counterparts; and b) how can we use this knowledge to enhance the performance of elite masters sprinters?

First up, it’s important to acknowledge that masters sprint performance is likely strongly linked to opportunity to performance. There aren’t many athletes in the older age categories, such as M85 or M90, which means that the strength of the World Record may be somewhat weaker. In addition, as masters athletes get older, they tend to train both less frequently and for less duration, and typically report lower levels of intrinsic motivation. All of these aspects may negatively influence performance. Finally, it’s not clear whether elite masters athletes get slower with age due to actual changes in physiology due to age, or because they train and compete less. Whilst we think it’s the former, the latter could well play an important moderating role.

That said, there are some important physiological changes that occur with age, and, my belief—a belief shared by my co-authors—is that these changes contribute to, and most likely drive, any age-related changes in sprint performance. We’re fortunate that there is a lot of research into elite sprint performance, and we understand that the key biomechanical variables are step length and step frequency. As a general rule, elite sprinters have longer step lengths than non-elite sprinters, but both groups have similar step frequencies. A number of variables underpin both step length and step frequency, of which a key one is ground contact time (GCT); elite male sprinters tend to spend less than 0.09 seconds on the ground per step, which is a shorter time period than non-elite sprinters. They also tend to achieve great hip flexion angles (i.e., their thigh gets closer to 90 degrees) than non-elites.

Whilst we don’t have as much data on the biomechanics of sprint running in elite masters sprinters, we do have some. Data collected from the World Veterans Championships in the early-1990s demonstrated that elite masters sprinters have shorter strides and less hip range of motion than their younger elite counterparts, along with a significantly higher GCT. These findings were replicated from the European Veterans Athletics Championships in the early 2000s. As a result, we can be pretty confident that elite masters sprinters are slower than younger sprinters because of reductions in stride length and hip angle, and increases in GCT.

Stride length and GCT are somewhat linked; if we spend less time on the floor, we can spend more time in the air, and therefore cover more distance. Shorter GCTs are related to being able to produce the required amount of force in a short period of time; if we want to reduce GCT, we need to either increase our ability to produce the required amounts of force in a shorter period of time, or reduce the amount of force we need to produce (i.e., reduce our body mass). Typically, we focus on producing more force in less time; this requires us to be both strong (to produce the force) and powerful (to produce the force quickly). We know from laboratory-based tests that masters sprinters have significantly lower scores in the Counter-Movement Jump (CMJ)—a test of power—and half squat one repetition maximum (1RM)—a test of strength—than younger sprinters. We also know that masters sprinters have significantly fewer type-II (fast twitch) muscle fibers when compared to younger sprinters. As such, we believe that masters sprinters are slower because they have less type-II muscle fibre, which in turn reduces their force-development capabilities, which in turn increases their GCT and reduces their step length.

However, whilst declining levels of type-II muscle fibre, and the associated loss of muscle strength and power, are an obvious driver of this reduction in sprint speed with aging, they’re not the only one. As we age, we tend to see degradation in the neurons that support muscular contraction, along with a decline in muscle quality; essentially, muscles become slightly harder to control and coordinate, and their “youthfulness”—ability to recover or move with quality—is reduced. This is a normal part of aging, driven by the accumulation of muscular damage that occurs over time. As an example, when we use a muscle, the motor units driving movement are innervated and denervated; over multiple cycles of this process, there is a slow accumulation of errors, which lead to a small number of muscle fibers that cannot effectively be activated to support movement. These fibers can’t be adequately utilized, and, as a result, atrophy over time. Similarly, these innervation-denervation cycles cause the body, in its search for efficiency, to “clump” together motor units that are situated closely to one another; this leads to a loss of movement coordination and control, making finer movement skills more difficult, and reducing movement smoothness over time. This, in turn, increases the energy cost of movement, along with the injury risk.

What does this all mean for the training of masters sprinters? Given the importance of maintaining muscular size and strength—especially in terms of type-II muscle fibers—training strategies which promote these aspects should be utilized. Research in younger athletes demonstrated the effectiveness of resistance training in enhancing strength, power, and hypertrophy, although there is little research exploring such interventions in masters athletes. However, those studies that have looked at this in detail suggest that such training interventions do adequately support sprint performance, and so should be prioritized. Given the age-associated loss of muscular coordination detailed earlier, training that stresses coordination ability and stability is likely to be effective in masters sprinters, perhaps more so than in their younger counterparts. Alongside this, training methods that promote muscle quality, such as isometric or eccentric exercises, may promote muscular remodeling and hence improve performance.

From a technical aspect, when sprinting horizontal force production is an important driver of success; however, masters sprinters have been shown to have lower levels of mechanical effectiveness of force application during sprint acceleration running. In one study, masters sprinters had less than half the mechanical effectiveness of younger sprinters. This loss of effectiveness is partially driven by losses of limb strength and hip extension capabilities, suggesting that horizontally orientated resistance training exercises may be very useful to older sprinters. Finally, in line with the degradation of neuromuscular control, a masters sprinter may benefit from an increased focus on exercises that may reduce the risk of injuries, such as eccentric loading activities for calf and hamstring, along with frequent exposure to high speed running.

Alongside these training interventions, changes to diet can also support the performance of masters sprint athletes. A major part of this is the maintenance of muscle mass, which can be optimized through intakes of dietary protein at rates of 1.2 – 1.8 g/kg per day, as well as 0.4g per kg bodyweight immediately post-training, Creatine supplementation appears to support high intensity training performance—and hence subsequent adaptations—in older sprinters, with intakes of ~5g per day recommended. Similarly, omega-3 fish oils may assist in limiting the anabolic resistance that has been shown to be present in older adults, making their muscles more responses to grow and repair post-training.

In summary, the training of masters sprinters should prioritize the maintenance (or even development of) muscle strength and power, specifically through targeting type-II muscle fibers, and prioritizing force development in the horizontally-orientated plane. By doing this, age-related reductions in GCT and stride length should be attenuated, and performance maintained as much as possible. Alongside this, training programs that prioritize neuromuscular control also appear important. Nutrients that support the development of muscle mass should also be utilized to support the training undertaking, allowing athletes to stay faster for longer.

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