Some clever and consistent readers might recognize this post from a couple months back. I believe, however, that understanding energy systems is essential to training athletes safely and effectively. Coaches that lack a basic knowledge of physiological responses to training and are unable to apply that knowledge are setting up their athletes for failure, at best, injuries, at worst. This is why we decided to place this post FIRST in our series for football players. I challenge to you, as you read this post, think about: a) the typical football conditioning sessions (football camps, practices, etc.)
b) contemplate the actual energy demands of the different positions, for example a running back has far different needs than a linebacker. Does it seem logical to train them the same way?
c) how can current football training sessions be adjusted to be more effective and allow for the desired physiological adaptations required by the various positions.
Let's dive in!
Energy systems training, or EST for you acronym lovers, has come to the forefront of SAPT's training programs for our high school athletes as new research has manifested about the importance of specifically training those systems. I advise you to grab a cup of coffee, this is a heavy one! (no pun intended)
ATP- the currency, if you will, of energy within the body. ATP (adenosine triphosphate) is an adenosine molecule with three phosphate molecules attached. The bonds that hold the phosphate molecules to adenosine are considered "high energy" bonds, meaning when they're broken a large amount of energy is released. This energy is harnessed by the cells within the muscle to drive function (aka: contractions). Simply, ATP makes muscle contraction possible and thus the glorious thing we call athletic movement. (And, well, movement in general.) The soon-to-be-mentioned energy systems regenerate fresh sources of ATP (through metabolic processes not important to know at this point) and their ability to produce ATP varies upon the duration of the exercise, the length of the recovery period, and the number of activity bouts. THIS IS IMPORTANT TO UNDERSTAND.
PCr/Alactic system- Provides immediate energy. The first couple explosive steps during a sprint or the clash of a tackle on the line, the alactic system kicks into gear. it's important, for example, for football conditioning programs to include exercises that challenge the alactic system. (think jumping drills, acceleration drills, MB throws, etc.) Thankfully, near SAPT Fairfax, we have a turf field that we can perform running drills for our youth athletes.
*note* PCr stands for phosphocreatine. This is a molecule each of phosphate and creatine. The bond between them is weak, and the creatine will quickly relinquish it's phosphate to reform the ATP. It's part of that metabolic process I mentioned earlier. So, theoretically, an athlete that can replenish PCr faster, can use their alactic system to a greater capacity.
Glycolitic/lactic system- Provides intermediate energy. For example, in a 100 m race, the alactic provides for first 6-10 seconds and the glycolitic takes over as the predominate source of ATP production for the remainder of the sprint. Or, in a prowler race, the second pass is entirely glycolitic.
Aerobic system- Provides long-term energy. This can be anywhere from taking a long, leisurely walk with your dog, to the brief rest period on the field between plays. Technically, watching TV is an aerobic activity since all your energy is being produced by the aerobic system. But, for purposes of this post, we'll consider aerobic system as the energy provider for the recovery time betwixt exercise bouts in athletics.
The initial thought was that energy systems turned on successively: the alactic system fired up it's ATP production for the first 6 seconds or so, then the glycolytic system took over until the 90 second mark, followed by the aerobic system for any activity lasting longer than 90 seconds. Recent research disproved this and demonstrated that all systems are working simultaneously full tilt to produce ATP as fast as they're capable of from the outset of activity.
The amount of ATP a system can contribute is dependent upon the power of the system and it's capacity.
Power = the rate which a system turns on and can produce ATP. The alactic system can start up the quickest, which is why it contributes so much at the onset of activity, while the aerobic system is a bit slower to get rolling.
Capacity = duration at which the energy system can produce ATPs at a given activity level. The alactic system can produce a lot of ATP at a high level of activity, but only for short while; in contrast the aerobic system sustainably produces the most ATP at lower levels of activity. Which is why one can't just sprint forever: the activity level exceeds the capacity of the alactic system to keep up with the energy demand. (good thing breathing doesn't exceed the aerobic system's capacity!)
The 1999 study but Parolin et al. asked the subject to perform three, 30 second sprint bouts on a bike followed by 4 minutes of recovery. The researchers sought to discover what was going on at a cellular level. One would postulate that the glycolitic system would be the predominate supplier of energy correct? Hold onto you hats, the curious researchers found that, over the course of those sprint bouts, the glycolitic system's contribution decreased! Check out this graph from the study:
First bout on the left (A) and the last bout on the right (B). "Oxidative phosphorylation" = aerobic system
As you can see, the alactic system still provides the bulk of ATP for the first 6 seconds or so of the sprint, but the aerobic system steps it up in the last sprint and the glycolitic's contribution is paltry at best. It's suggested that the accumulation of the glycolitic by-products limits it's ability to continue functioning, thus the aerobic system is tapped into in order to supply the ATP. There's another study here demonstrating similar effects if you care to check it out.
Ok, geeky strength coach, how does this relate to me and my training? A majority of sports, outside of the endurance sports (cycling, cross country, swimming, etc.) consist of short, intense bursts of activity followed by longer periods of rest. Think of football player: the actual play lasts somewhere between 5-15 seconds, followed by 1-3 minutes of mulling around. Same thing with any other field player, soccer, lacrosse, field hockey, football, etc. are all short sprints followed by longer periods of low intensity jogging.
Even lifting is an alactic/aerobic sport!
Gotta recover from that pull!
If a majority of athletes rely on the alactic and aerobic systems for energy production, why employ training methods like windsprints, suicides, and sprinting 400s, usually I might add, utilizing little to no recovery? Training the glycolitic system (which all these methods tend to do, since the activity bouts are usually longer than 10 seconds with inadequate recovery) actually hurts these athletes. Without a well-developed aerobic system, the athlete has no choice but to dip into the glycolitic system for energy production over repeated bouts of activity, and as demonstrated, the glycolitic system is limited because of the build up of by-products. Fatigue and decreased power output are the only options at this point. Not good.
Since this month's articles are dedicated to training football players, which are, conveniently, power athletes. This information is a game-changer when it comes to training.
Remember the PCr from up top? The essential ingredient to a high-capacity alactic system? Guess what replenishes PCr the best during the recovery periods... the aerobic system. Not only does the aerobic system contribute ATPs, it indirectly supplies ATP by helping out the alactic system by providing it the substrate (PCr) it needs to function. Power athletes NEED a solid aerobic base in order to perform at a high-intensity level without fatiguing before the end of the game/match.
Whoa, now, Kelsey, it sounds like you're advocating long-distance running for power athletes. No, I'm not. Let's be clear, a jog now and then won't hurt (especially if it's a REEEEALLLY nice day) but it should NOT, I repeat NOT, be the main focus of aerobic training. This especially applies to athletes that already stress their joints repeatedly during their sports.
I would qualify that as "stress" on their joints.
At SAPT, we help build the aerobic base, then back off to a maintenance level while focusing on the power/strength component of athletic preparation for our high school athletes. I wrote about the benefits of training sprint work here.
To build the aerobic foundation, at SAPT we like to throw in cardiac out put circuits as a joint-friendly conditioning for our high-impact athletes (football and rugby players). Since this post is insanely long already and Steve did a spectacular job of explaining and providing samples of cardiac output circuits, I shall direct you here. The biggest take away is this little gem:
Perform the following in circuit fashion, keeping your heart rate roughly in the 120-150bpm range. Many people like to get way too crazy with these and push their heart rates through the roof (due to all the rage of high intensity training). Resist this urge, and take a moment to rest if your heart rate shoots above the desired range.
That keeps the athlete OUT of the glycolitic system's domain and in the alactic (the exercises) and aerobic (rest in between). Ladders are another great way to train your aerobic system without stressing the joints too much and build strength.
Am I saying that you should never run repeated sprints? No, especially if you're a track athlete, but for the power athletes, maintaining a solid aerobic system while training strength will produce ideal effects.
Main Points to Remember:
- If you're a power athlete, the bulk of your conditioning work should focus on building the aerobic system through cardiac output circuits, ladders, or sprints/hill sprints (with full, adequate rest). A little goes a long way, so don't go crazy and sacrifice your strength for your aerobic training. Once the foundation is laid, one or two training sessions a week (max!) should be dedicated to training the aerobic system (especially if the sports season is in play, in that case, athletics will take care of most of it). This is a point that's going to go against the football grain; more is NOT better (we'll be elaborating on that later in the month). I see so many coaches running their athletes into the ground; it's not going to make them better football players.
- The glycolitic system is not evil, and still needs to be respected, however, training modalities that rely on the glycolitic system (repeated sprints/exercises with little to no rest) are not as useful to power athletes a) do not mimic most athletic energy demands, b) cause fatigue faster (thus masking true fitness or strength) and c) due to fatigue during the training session, injuries are more likely.
- It's still all about strength!