Fatigue is one of the most poorly understood concepts in the fitness industry. There is a pervasive tendency to consider fatigue as a sensation. In fact, fatigue is merely a reduction in the ability of muscles to exert force during exercise. It is accompanied by feelings of effort and discomfort, but the fatigue itself is separate from these sensations.

Fatigue is caused by multiple processes that can occur inside the central nervous system (CNS) and inside muscles. Whenever fatiguing processes occur inside the CNS during a bout of exercise, high levels of motor unit recruitment cannot be achieved. This is known as CNS fatigue.

What is CNS fatigue?

CNS fatigue is defined as a reduction in our ability to voluntarily activate a muscle in a maximal effort. This reduction in voluntary force necessarily requires either a decrease in motor unit recruitment levels, a reduction in motor unit firing rates, or both. Either change will lead to a reduction in mechanical tension experienced by the muscle fibers of high-threshold motor units because the size principle is always followed.

CNS fatigue likely occurs as a result of three mechanisms: (1) a decrease in the size of the excitatory input to the motor neuron, (2) an increase in cortical inhibitory input to the motor neuron, and (3) a decrease in the responsiveness of the motor neuron itself. Although the nature of these mechanisms is still unclear, increases in cortical inhibition may perhaps occur due to (1) afferent feedback from interneurons known as Renshaw cells (which are activated by neural drive from the motor cortex and afferent feedback from muscles), as well as (2) direct afferent feedback from group III and IV afferents.

Our ability to voluntarily activate a muscle can be measured by testing our maximum strength using paired voluntary and involuntary efforts (by stimulating the muscle electrically or with transcranial magnetic stimulation). The extent to which force produced in the involuntary effort is greater than in the voluntary effort indicates the level of voluntary activation.

Importantly, CNS fatigue can occur during both submaximal and maximal contractions, and the underlying mechanisms are quite similar in each case, (although their proportional contribution to CNS fatigue might well differ). Indeed, contrary to popular belief, it is unnecessary to exert high forces or achieve high levels of muscle activation to produce CNS fatigue. In fact, CNS fatigue occurs readily when performing extended durations of exercise that involve very low forces, including aerobic activity. As we will see, this point is particularly important for understanding how CNS fatigue affects strength training practices.

Why is CNS fatigue important?

When CNS fatigue occurs, voluntary activation is reduced. This means that either the number of motor units that are recruited decreases or their firing rates decrease.

Since motor units are always recruited in size order, this means that the highest threshold motor units (which control the largest numbers of the most highly-responsive fibers) are derecruited, or their firing rates are reduced. Consequently, when CNS fatigue occurs, these important muscle fibers are stimulated to a lesser extent (or even not at all) after a workout. This means that less muscle growth will be stimulated.

Importantly, the failure to achieve maximal levels of motor unit recruitment occurs even when we train to muscular failure. This is because “muscular” failure is actually caused by both CNS fatigue and local, muscular fatigue.

What is afferent feedback?

Afferent feedback is one of the mechanisms that could lead to CNS fatigue during strength training. Indeed, group III and IV afferent signaling from a trained muscle does seem to reduce voluntary activation, likely by increasing inhibitory input to the motor neurons. Afferent nerves can influence both spinal and supraspinal neurons, so such signaling could cause CNS fatigue with or without affecting the size of the initial signal from the motor cortex.

The role of afferent neurons is to transmit information detected by sensory receptors in various parts of the body to the CNS. Afferent neurons are classified into groups according to their size, with group I being the largest and groups III and IV being the smallest. Group I and II afferent neurons are linked to muscle spindles and Golgi tendon organs. Group III and IV afferent neurons are linked to a range of sensory receptors that detect changes in the mechanical loading of muscle fibers and of their metabolic environment. These are therefore the afferent nerves that are most likely to trigger CNS fatigue during exercise.

Indeed, the mechanical loading produced by the muscular contractions that cause peripheral fatigue, and the metabolic changes that are associated with peripheral fatigue (and in certain cases also cause peripheral fatigue), can therefore stimulate group III and IV afferent nerve signaling.

The firing of group III and IV afferent neurons seems to be a normal response to all muscular contractions, even those involving very low levels of effort. Yet, by direct measurement of neuron firing, several studies have found that group III and IV afferent nerve signaling is increased by blood flow restriction, likely due to the greater stimulation of metabolite-sensitive afferent nerves, because of the faster rate of metabolite accumulation that occurs when muscle oxygenation is reduced. Also, injecting potassium, lactic acid, and arachidonic acid into a muscle activates group III and IV afferents and also causes muscle pain and the sensation of muscle fatigue. Even so, several studies have shown that aerobic exercise involving low external forces is a very effective form of exercise for triggering CNS fatigue, so it may be that the duration of time that the muscle produces afferent feedback is more important than the level of afferent feedback itself.

Does CNS fatigue happen during and immediately after a set of strength training?

Some strength coaches and researchers have proposed that there is minimal CNS fatigue during a set of strength training exercises, and also minimal CNS fatigue immediately afterward.

If this were true, what would it mean in practice?

• Immediately after a set of strength training exercises — if there were no CNS fatigue immediately after a set of strength training exercises, it would be possible to perform multiple sets that involve maximum levels of motor unit recruitment with minimal rest periods. We could program short (≲1 minute) rest periods and achieve the same amount of hypertrophy as long (≳3 minutes) rest periods (this is definitely not true).
• During a set of strength training exercises —if there were no CNS fatigue during a set of strength training exercises, motor unit recruitment levels would increase with increasing local muscular fatigue all the way to maximum levels at muscular failure, regardless of the weight on the bar. Strength training workouts involving the same number of sets with any weight performed to failure would then cause the same amount of hypertrophy (this seems to be somewhat, but not entirely true).

Contradicting the first claim, there is good evidence that CNS fatigue occurs immediately after a workout of fatiguing contractions. Such reductions in voluntary activation can last for up to 30 minutes. This prolonged suppression of motor unit recruitment levels may help us to explain why short rest periods are less effective for muscle growth than longer rest periods, as taking a short rest period involves training while still experiencing CNS fatigue from the previous set.

Contradicting the second claim, there is also good evidence that CNS fatigue develops progressively during sustained maximal and sustained submaximal isometric contractions. Yet, there is less evidence for CNS fatigue developing over the course of a set of dynamic contractions. Also, research suggests that isometric contractions cause more CNS fatigue than dynamic contractions, perhaps due to the continual compression of the vascular structures, which prevents metabolites from leaving the muscle, thereby increasing afferent signaling. Even so, it seems likely that CNS fatigue does occur gradually over a set of normal strength training exercise, in exactly the same way as it does in sustained isometric contractions.

Therefore, we can conclude that CNS fatigue develops throughout sustained isometric and dynamic contractions, in addition to after a set of muscular contractions, and it can last for up to 30 minutes. This CNS fatigue likely explains why short rest periods are less effective for hypertrophy than longer rest periods, and likely also explains why very light load strength training to failure does not work as well as strength training with heavier loads.

Does CNS fatigue really accumulate over a strength training workout?

CNS fatigue does indeed accumulate over a multiple set workout. This key finding has two key implications.

Firstly, it implies that there is a diminishing effect of adding extra volume for a muscle group to a workout. Each incremental set will have a progressively smaller and smaller effect, due to the increasing level of CNS fatigue. Even so, the research into the dose-response of training volume on muscle growth is currently somewhat unclear, due to the publication of some studies showing the increased effectiveness of quite high volumes.

Secondly, it implies that exercises that are performed later in a workout will produce smaller effects than those performed earlier in the same workout. This effect has been observed consistently to date.

Does CNS fatigue happen to a greater degree during strength training involving lighter loads?

External loads during strength training can be readily subdivided into four different categories: heavy (1–5RM), moderate (6 –15RM), light (16–30RM), and very light (lighter than 30RM), although the exact dividing line between light and very light loads is fairly hazy and certainly debatable.

Many researchers have assumed that the magnitude of the external load is what determines the mechanical tension in a set of muscular contractions. This assumption is *totally* invalid, because of how muscle fibers experience mechanical tension in muscular contractions. In fact, the magnitude of the external load has no impact on the mechanical tension that is experienced by muscle fibers in a contraction. The only factor that determines the mechanical tension that fibers experience is the force that they exert, which is largely determined by the force-velocity relationship. And when doing every rep with maximal effort (and thus ensuring maximal levels of motor unit recruitment) the contraction velocity of the working muscle fibers is determined solely by the proximity to muscular failure and not by the weight on the barbell.

Therefore, it is the proximity to muscular failure that determines the level of mechanical tension on each working muscle fiber, and not the magnitude of the external load. Consequently, when training to muscular failure, the level of mechanical tension experienced by the working muscle fibers is the same regardless of the weight on the bar.

Yet, research has shown that very light load strength training to failure causes less muscle growth than light, moderate, or heavy load strength training to failure. Since the mechanical tension that is experienced by working muscle fibers is the same when training to failure regardless of the weight on the bar, very light load strength training must involve lower levels of motor unit recruitment (or firing rates) than the other loads due to CNS fatigue, because only this can reduce a meaningful large proportion of the fibers in the muscle from working and experiencing mechanical tension.

This exact phenomenon has been observed when assessing the effects of fatigue during isometric contractions at different levels of force on (1) the maximal level of motor unit recruitment that can be achieved, and (2) the amount of CNS fatigue. Indeed, when performing fatiguing submaximal isometric contractions to task failure, motor unit recruitment increases to higher levels when using higher forces (70% of maximum force) than when using lower forces (30% of maximum force). Also, voluntary activation (as tested in periodic maximum contractions) decreases to a lesser extent when fatiguing contractions are done with a higher force (45–75% of maximum force) than when they are done with a lower force (30% of maximum force).

It seems likely that this CNS fatigue occurs due to the longer duration of exercise that is required in order to reach task failure with lower forces, perhaps due to the longer duration of time for which the muscles experience afferent feedback. Indeed, several studies have shown that aerobic exercise involving quite low external forces is extremely effective at triggering sustained CNS fatigue. And some of this research hints that longer durations of aerobic exercise may cause more CNS fatigue than shorter durations.

Therefore, we can conclude that CNS fatigue develops to a greater degree when performing strength training sets of longer durations, such as are required when using lighter loads. This CNS fatigue likely explains why very light loads are less effective for hypertrophy than light, moderate, and heavy loads. The lack of any obvious difference in muscle growth between light, moderate, and heavy loads suggests that the effect may be non-linear. CNS fatigue may increase exponentially when load (rep range, in reality) is reduced below a certain threshold (likely between 20–40% of 1RM).

N.B. Increases in voluntary activation after training

It is worth noting that long-term studies that have assessed the effects of light load strength training (often in conjunction with blood flow restriction, although this is not really relevant) have reported no increases in voluntary activation, which suggests that there is no stimulus to increase the number of recruited motor units during that type of exercise. If peripheral fatigue during light load strength training did indeed cause a gradual increase in motor unit recruitment all the way through to maximal levels, then we would naturally expect this stimulus to lead to an adaptation in voluntary activation levels. Since this does not happen, we might reasonably infer that motor unit recruitment levels are never truly maximal during light load strength training.

What are the practical implications?

Understanding how and why CNS fatigue occurs in a workout is important for writing any training program intended to cause hypertrophy, because it can affect the rest period duration, exercise order, relative load, and volume that we select.

Additionally, due to its responsiveness to the presence of muscle damage, CNS fatigue affects training frequency and the use of aerobic exercise in the same training program as strength training (concurrent training).

To mitigate the effects of CNS fatigue, we can use longer rest periods between sets and prioritize the most important exercises by placing them first in a workout, because CNS fatigue will occur after each set in the workout, and it will accumulate gradually with each additional set. We can use moderate and heavy loads since these involve performing fewer total reps to achieve the same hypertrophic stimulus as light loads. Finally, we can be aware that simply adding extra volume to a single workout may not necessarily produce incrementally superior effects, and dividing a single workout into more frequent workouts over the week may sometimes lead to better results.

What is the takeaway?

Fatigue during strength training involves a reduction in our ability to exert voluntary force. This reduction in voluntary force occurs due to fatiguing processes within both the CNS and also within the muscle. When fatigue occurs due to CNS fatigue, this suppresses the level of motor unit recruitment that can be achieved, which in turn stops large numbers of highly-responsive muscle fibers from being trained during the set.

CNS fatigue accumulates during sets of strength training, which prevents full motor unit recruitment from being reached despite reaching muscular failure. This seems to occur to a greater extent when the duration of a bout of exercise is greater, possibly due to the greater time that the muscles spend producing afferent feedback. This can explain why very light loads are less effective than light, moderate, and heavy loads for producing muscle growth.

CNS fatigue lasts for several minutes after each set of strength training and accumulates over a workout. This can explain why short rest periods are less effective than long rest periods for producing muscle growth. It can also explain why exercises that are done earlier in a workout lead to more muscle growth than those that are done later, and why increasing training volume does not seem to have a linear dose-response effect on hypertrophy.

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Despite our already digitized world, 2020 was certainly the year where everything went virtual. From school and work to our social lives and activities, our plugged-in world has been amplified with new technology to adapt to the puzzles of the pandemic. In a rapid tech revolution rarely seen once in a generation, no industry has gone forth unaffected.

The sports world has catapulted headlong into this new virtual reality, applying video training and virtual competition at every level. Amenity Odisha FC Soccer School in New Delhi, India has created an innovative solution to the lack of scouting opportunities by holding a virtual skills contest for the chance to win a scholarship. Certainly a unique opportunity, this contest highlights the ingenuity within the world of soccer technology while keeping within the bounds of a typical scouting process.

In Monterey County, CA, youth players for the local boys and girls club are being encouraged to play outside with training kits and QR codes for virtual training sessions hosted by professional players. This program provides local kids the incentive to play outside amidst a pandemic that has limited these opportunities for young players.

While both of these programs represent helpful and immediate solutions for players in these areas, an eventual return to normal play would certainly spell the downfall of these solutions. The customization and hands-on attention granted by human coaching is irreplaceable by stagnant video training, and such programs as the one in New Delhi leave room for an uneven playing field because of variation in training equipment available to different contestants.

Of course, there is no doubt that virtual training solutions will remain a strong part of the future of training and player development for all soccer and the rest of sports. The key to creating sustainable products in the virtual training world that last beyond the pandemic comes with an ability to integrate the best aspects of human training into the virtual environment.

Most notable of these aspects are a coach’s ability to customize drills according to the skills and motivations of each player, something not possible within the limitations of typical virtual training. With current methods, many athletes are liable to feel overlooked and marginalized as virtual coaches prove incapable of meeting their specific training needs.

Furthermore, coaches have a unique ability to build an emotional and psychological understanding of their players that can be supported by virtual training tools but never replaced by it. Playform’s compatibility with the human elements provided by real coaching is why the flagship app represents a truly sustainable training tool with utility beyond the limitations of the pandemic. By giving coaches the ability to track player data and progress, Playform provides statistical assurance to the organic ways in which coaches observe and drive the development of their players.

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It’s safe to say that, if you want to work on starts and first step quickness, curved treadmills are bad speed tools. Upright running seems fine, but every coach that uses a treadmill needs to see the big picture and ask themselves what they expect to happen differently than running on the ground, specifically the grass or track. Is it to help teach? Is it to help condition the neuromuscular system differently?

Treadmill running is about conditioning, not top speed development. While technically, any training that an athlete does contributes to their success, there are differences between a maximal all-out sprint and a curved treadmill maximal sprint.

What Does the Science Say on Curved Treadmills?

I will back up my logic and reasoning with additional peer-reviewed science and my own data collection. It seems the research on treadmills and sprinting is not a priority, so I will share what is available and what I know from measuring the variables that matter.

In my investigation, the studies showed the value of a curved treadmill, but didn’t really address the differences between ground-based running much, if at all. A few studies noted the challenges with non-motorized running and how they are generally not comparable. Overall, the studies seem to dodge the simple question: What is different between running on a curved treadmill and on the flat earth?

Overall, I wanted more range on the total number of studies, and some of the depth of the research was solid. A few of the studies were fascinating and important to those with specific health needs. The best example I found was on Parkinson’s, a neurological disorder affecting millions. My own grandfather struggled with this heinous disease, so I was excited to see that walking on a curved treadmill had potential benefits for improving walking for those with Parkinson’s.

Study 1: Reliability of the WOODWAY Curve Non-Motorized Treadmill for Assessing Anaerobic Performance

I was confused about the purpose of this study, as it seemed to be stuck in a comparison between a Wingate test and a curved treadmill, while attempting to show how the treadmill is useful for athletes. The researchers used recreational subjects who performed 30-second “sprints” at 6 meters per second at peak velocity. It was a relief that the researchers, in their conclusion, were very aware that the speed was not a representation of true sprinting. The researchers did not validate the data accuracy of the treadmill or show how sports could benefit from the equipment besides for fatigue monitoring. It is worth noting that the primary goal of the article was to find another option besides conventional Wingate testing.

Study 2: A Self-Paced Intermittent Protocol on a Non-Motorised Treadmill: A Reliable Alternative to Assessing Team-Sport Running Performance

This interesting study researched 10 (mixed) team sport athletes in their 20s to see if the treadmill’s non-motorized component could be useful for reliability testing of self-paced running. The researchers investigated two questions: how the treadmill could fare in a simulation protocol for reality, and how quickly the athletes could familiarize themselves with the curved shape.

The results were exactly what a sport scientist would ask for, but I was concerned that the maximal sprint was in the 6 meters per second range again. After a while, I wondered if any true maximal velocity work was done in the research. A good takeaway is that the curved treadmill allowed for self-pacing, which supports the idea that it’s generally more natural than paced options like motorized treadmills.

Study 3: Non-motorized Treadmill Running Is Associated with Higher Cardiometabolic Demands Compared with Overground and Motorized Treadmill Running.

This study on cardiometabolic demands of a curved treadmill is one of the stronger studies. It used isometric pulls and countermovement jumps to evaluate athlete power—not bad for an “endurance” investigation. I expected no less from Australians, who tend to do a better job adding power complements to endurance studies that are physiological in nature.

While this doesn’t prove that a curved treadmill (specifically the WOODWAY Curve) isn’t useful for testing conditioning, it does show that we need to look at all of the treadmill systems differently. It was fascinating how the study looked at athlete body mass to see the relationships of the belt friction and athlete build. We will eventually need to address how this research data will benefit prescription in training.

Study 4: The physiological and perceptual demands of running on a curved non-motorized treadmill: Implications for self-paced training

This article on curved treadmills from Runner’s World gave a mixed message to those who didn’t read the full study. Most would consider a system that adds more demand on the body to be a positive benefit, but I see it as a mixed bag.

What is great is that those in fitness who want a more demanding workout can see the research study as proof that they get a better workout by burning more calories. If they want to elevate their heart rate with a higher demand from the equipment, that is fine, but I am suspicious about adding less-efficient running as a resistance modality. True, the 25-30% jump in physiological demand is interesting, but how that metabolic load improves speed or performance remains a mystery to me. Adding a weight vest or running on an 1% grade is a theoretical overload, and I have no confidence that this would make athletes faster even in endurance sport, let alone sprinting.

Study 5: The Effect of a Curved Non-Motorized Treadmill on Running Gait Length, Imbalance and Stride Angle

My favorite of the five studies shared the effects of running on the ground after spending a few bouts on the TrueForm, and the results were subtle but still notable. The researchers made a little bit of a leap of faith when saying the device was responsible for improving running economy through a decrease in contact time, but it’s the only study I know that looked at curved running to test if it made a difference in running on the ground later. If the TrueForm can do this at slower speeds, the next question is how much influence it has on sprinting. A reduction in contact time with lower-level recreational athletes running is not the same as maximal velocity sprinting with an elite.

These studies all had excellent insights into curved treadmills, but they were not very exciting for understanding the kinetics and kinematics of the device compared to regular running. What was most interesting to me was the study on the effects of using curved running and stride parameters immediately afterward.

My Investigation of Curved Treadmill Running

The above studies showed progress in understanding the interaction of foot strike and the curved product, but they did not really connect to maximum speed or get into solid direct measures of function. Therefore, I had to do the very simple science of comparing estimated kinetic and high precision kinematic evolution of the device. I looked at four systems, all having various friction levels of the treads and slightly different designs of the curve, including radius and slope. Simply put, each system was similar enough to summarize the findings on the differences between running on the ground and on a curved treadmill. WOODWAY did have a slightly lower friction point, so the belt speed was a little faster, but the design recruited the lower limbs in a more demanding manner metabolically.

The kinematics of running at 9-10 meters per second (calculated) were like fast intensive tempo running, but the pressures were different and the electromyography was also different. The differences were big enough to be seen visually compared to running 22- to 25-second 200m reps. I did not test all-out sprinting, as the athletes didn’t feel comfortable hitting a maximal effort and I purposely wanted it as fast as tolerable.

Some athletes felt more resistance on the less-expensive models, while other athletes felt that they were slipping early in touchdown. As the speed increased, either the treadmills became more demanding on hip extension or the athlete cut off their stride to improve front-side positioning of their running mechanics. I didn’t have a sample size statistically powered enough to see a conclusive group trend, as everyone tended to respond differently.

Vertical oscillation of the center of mass and leg stiffness were significantly lower, and athletes had more gradual rises in pressure compared to ground running. The grab velocity was very high with the better equipment (WOODWAY) and I didn’t have a basketball player tall enough to see whether the curve radius was appropriate for the jogging speeds seen in rehabilitation programs. Overall, the response was enough that such small differences would show up metabolically locally and globally.

Not all muscles worked harder, as some lower leg muscles below the knee seemed to decrease their activity, but again, this was a small sample size. I didn’t look at rotation velocities or rear foot motion in great detail, but any coach with a Dartfish video app can film from behind and from the side to triangulate how much difference in foot strike is occurring. We didn’t do more than three trials, so it’s hard to see if the familiarization with the equipment “saturates” after a few weeks or not.

The main takeaway of the curved treadmill is the fact that the athlete is running in place and theoretically able to receive instruction and perhaps work on technique, whether rhythm or something similar. I am not aware of technical development dependent on this approach, nor do I have any experience using the equipment for extended periods of time. In my opinion, the curved treadmill has some possibilities with stride change, but so far, there has not been much concrete evidence of stride changes coupled with improvements in speed demonstrated in the applied setting.

A Summary of Pros and Cons

Overall, curved treadmills are useful for getting a workout in, but I don’t know whether they are appropriate for rehabilitation or elite training. The differences in kinetics and kinematics remind me of resisted sleds, as the changes or possible negative motor skill influences might be mitigated with the development of power, so it’s hard to say that running on it in small doses is a problem. For the average Joe, conditioning is not something I would worry about. Anything that can deliver a safe and effective way to challenge the body to me is good progress.

Pros for Curved Treadmill Running

The cost of a curved treadmill makes it an interesting option for those who want to get a great workout done in less time, and provide a specific resisted running option for the masses. Curved treadmills allow for self-pacing and possible anaerobic testing alternatives to Wingate assessments.

Cons for Curved Treadmill Running

Based on the limitations of curved running, the equipment is a tempo replacement or alternative running option if an athlete needs a different modality than conventional running. Curved treadmills don’t provide the vertical force oscillation necessary to help with replicating maximal speed development, and can’t provide acceleration postures necessary for short sprinting.

You will have to decide if curved treadmills are a good choice for your situation. I am convinced that they have great value for the general fitness population, and are an interesting option for recreational runners, a creative interval option for performance running, and a possible benefit to sprinters in some circumstances. It will take a few mores studies for the science to catch up to the technology, but curved treadmills are popular and their use is growing.

Before You Run on a Treadmill Again

I am not against treadmills. I use them in the winter if I am traveling up north or when the weather is not cooperative, but only when walking with a weighted vest on a very small incline. I am more than aware of the popularity of treadmills, especially curved ones, with sprinters and runners. What I recommend is matching your needs with the right training approach, not just jumping on a curved treadmill and hoping for the best.

The current pros and cons are very embryonic, and over the next 10 years expect more research to potentially expand the list of benefits and limitations of the equipment. Don’t be scared to run on a curved treadmill—they are fine for fitness and great for getting a workout done in less time, but they are different than running on the ground.

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Hydration is fundamental to many physiological processes in and out of sports. With even a loss of 1% in body mass due to dehydration, you can expect your athletic performance to suffer. Dehydration increases core temperatures, speeds up carbohydrate oxidation, and muscle glycogenolysis. This simply means you are going to go through your energy reserves faster than if you were staying hydrated.

Dehydration will also attenuate strength (by ≈2%), power (by ≈3%), and high-intensity endurance (by ∼10%). To make matters even worse athletes who lose as little as 1–2% of their body mass through sweat loss exhibit an increase in heart rate, as well as a decrease in cardiac output, cognitive awareness, anaerobic power, and a decrease in time to exhaustion. Additionally, inadequate replacement of sodium, the predominant electrolyte lost through sweat, is thought to exacerbate the decline of these factors.

The promise

There is no one size fits all hydration plan for anyone to address dehydration-associated performance losses. Every athlete has a unique sweat rate and amount of sodium lost through sweating. A tailored hydration plan is what an athlete needs to mitigate the loss of performance due to dehydration.

Testing

The simplest way to measure your sweat rate is to weigh in before and directly after activity, and then modify rehydration based on findings. If weight was lost, hydrate more. If weight was gained, hydrate less.

Testing for sodium loss isn’t as straight forward. Tests aren’t something typically done at home. There are some urine strips that can help you understand sodium pre and post-activity but blood tests and the use of the LAQUAtwin Na+ meter are used as a simple test to determine the Sodium ion content of sweat. While an “easyish” method of testing the cost of this meter and others may be prohibitive some athletes.

The timing

When should you be concerned with hydration and electrolytes? Any activity lasting longer than 15 minutes should include the drinking of water. Any strenuous activity greater than 30 minutes should also incorporate electrolyte replacements. Any easy to moderate activity greater than 60 minutes should also incorporate electrolytes. Any activity when the heat and humidity together are high should include electrolytes.

How often

I subscribe to the slow drip method of hydration which means taking a pull from a sports bottle every 5 minutes. Dehydration can actually blunt your desire to drink so when you do get thirsty when it is hot and you have been active at any level for a while it’s often too late to rehydrate without stopping activity altogether and seeking cooler shelter. I recommend 24 oz an hour of activity to start but your sweat rate and current level of heat acclimation may require more or less. The only way to know for sure is to weigh yourself pre and post-activity.

Recipe

In a bike or sports, bottle add the following

The appropriate number of drops of Lyte Show electrolyte mix to the size of the bottle you will be using
2 TBSP of either Lemon Juice, Lime Juice or Cherry Juice
1 packet of raw turbinado cane sugar
2 TBSP of Raw Organic Honey
Optional – Pinch of sea salt

Links to Ingredients

• Lyte Show
• Sea Salt
• Raw Cane Sugar
• Raw Honey
• Lemon Juice
• Lime Juice
• Cherry Juice

Links to helpful kitchen items

The evidence

Since the early 1990’s there have been significant advances in hardware to track and measure human motion.  Cameras, electromagnetic trackers, and inertial measurement units to track the position and orientation of the body; EMG sensors to track muscle recruitment; EEG sensors to monitor brainwaves that initiate recruitment; and eye-trackers to identify stimuli that generate movement are all examples of hardware used to study human motion.  Because of these hardware advances and the research of human motion, there has been a huge impact on the academic disciplines of Physical Therapy, Athletic Training, and Performance Enhancement.

And these advances have now made their way into athletics at the professional level.  Many of the professional baseball and basketball teams have former biomechanists and athletic trainers from academia on their staff as they seek to prevent injury and enhance performance.  And the recently formed Baseballbiomechanics.org is one indication of the inroads made thus far.  We see this trend accelerating to the university and collegiate levels.  And private performance enhancement companies such as Driveline and Jenkins Elite are also getting into the act with services targeted at the high school level.  Many of these programs rely on advanced hardware.

One question often asked by coaches and staff is where do I start?  Equipment that fueled research is often considered too expensive and too difficult to use effectively in a coaching or team setting environment.  Our recommendation is usually “force plates.”  Force plates are portable, easily connected to computers, and work well when evaluating large numbers of subjects.  When joined with the right software, force plates will provide information on the power and speed that an athlete can generate.  And as budgets increase, force plates provide the base platform of an integrated system for tracking and measuring human performance.

What is a force plate?

On one level it can be described as a glorified bathroom scale.  It measures weight or more accurately, the force your body exerts onto the surface of the plate.  For use in performance enhancement, most force plates will have 4 sensors that allow the measurement of both the lateral force as well as the vertical force (3D) being applied to the plate.  This 3-dimensional force vector is necessary to accurately measure the reaction forces being applied to the bottom of the feet. There are 1- dimensional force plates on the market which measure only vertical force eg. ForceDeck.  One-dimensional plates typically have a lower price tag because of reduced hardware and engineering costs. However, the tradeoff is that they cannot be expanded to provide kinetic data. As you can see, force plates are much more than a bathroom scale and have a price tag to match!

There are several manufacturers of 3D force plates with the more well-known being Bertec, AMTI, and Kistler.  These are manufactured in ISO facilities with a precision acceptable for research and performance.  Wherever purchased, it is important to understand the specifications for expandability, frequency, noise, and sensitivity before purchase.

Why are people using force plates?

Force plates are being used by many different disciplines and for different reasons.  At the academic research level, force plates are an integral part of understanding the biomechanics of movement and the force and moments experienced at different body joints.  Force plates are also an important tool for understanding balance and the organization of the vestibular system.  At the coaching level force plates are used to quickly evaluate the power and speed of large numbers of candidates.  Jump Analysis products provide a consistent testing protocol that quickly generates reliable and relevant measures of subject ability to generate power. These metrics are applicable to a wide array of sports, including those which may not be obvious, such as running. Dr. Matt Jordan touched on many applications of Jump Mechanics in his recent talk at the 2021 Sports Biometrics Conference. Strength and conditioning coaches can quantitatively monitor progress achieved by each participant over a training cycle or help evaluate the effectiveness of alternative training programs as described on P3’s website.  And increasingly, force plates are being used to aid the return to play decision.  Balance, symmetrical power output, and performance relative to pre-injury levels can be factored into the decision with the aid of force plate data.

Role of Software

Perhaps more important than the Force plate itself is the software that will be used with the plate.  Some software is special purpose in the sense it is used for a particular application.  SwingCatalyst is an example of a force plate being used with software to analyze a golf or baseball swing.  Hawkin Dynamics software is an example used to analyze jump ability.  The MotionMonitor xGen is used for a variety of biomechanics-related applications, including jump assessment, kinematics for general sports movements, golf, and baseball swing analysis, real-time audio and visual feedback for training, and more. Expandability to include other hardware is an important feature.  The ability to synchronously collect motion capture, reference digital video, EMG, or eye-tracking data allows for a more complex analysis of an athlete’s movements.  For example, a recent publication from The Sports Surgery Clinic that included the collection of kinematic data revealed injury risks that were not observable from force plate data alone.  The MotionMonitor xGen’s Jump Pro offers a scalable solution that can be upgraded to include any of its supported hardware and software applications. The short video of a Baseball application below is an example of an upgraded application that includes full-body 3D motion capture in addition to force data.