A while back, Vic Ferrari said in one of Lowetide’s game-day threads (and damned if I can find it now) that he didn’t see why it was such a big deal to play goalies in back-to-back games, and that it really shouldn’t be that physically exhausting, or something to that effect. At the time, I gave some rudimentary response that covered the basics, but I wanted something a little more detailed that I could post over here and point to for future reference. After a month of procrastination and scheduling conflicts, I finally managed to get in to see my lab supervisor and muscle physiology professor, Dr. Douglas Syme of the University of Calgary, to clarify a few things and make sure I’d covered all the angles, no pun intended.
The first thing that must be distinctly understood is that goaltending, more than any other position, requires both speed and power in movement. While goalie pads have gotten much lighter and less absorbent since the leather pads of yesteryear gave way to sleek, modern synthetics, over the course of a game, those things still get soaked in sweat and snow from the ice, and get heavy as hell, requiring a lot of force to move. On top of that, you have to move them very quickly: goaltender response times are often on the order of hundreds of milliseconds. This creates a number of problems, which I’ll deal with in turn.
First, force generation and speed of contraction are inversely related, on a roughly hyperbolic curve. This means that the faster a muscle contracts, the less force it can generate. This makes sense when you think about it: if you contract your biceps as fast as you can, you might be able to make a hell of a smacking noise, and cause something to move by transferring momentum, but you aren’t going to be lifting much. Conversely, when lifting a very heavy weight, you can only lift it very slowly. While goalie pads are much lighter these days, there is a base amount of force needed to move them, which limits how quickly a goalie can move. Since the force produced by a muscle decreases the faster it moves, and a goalie usually wants to move as fast as he can, in order to move a given object quickly (glove, pad, stick, etc.), he really needs to exert himself.
Second, a goalie’s movement must be precise. In order to get a glove on a puck, Dwayne Roloson has to time his arm movement so that his hand is in front of the puck as it arrives. If his hand is more than a couple of centimetres off course, he has to quickly readjust. Further, there’s positional recovery to consider: when Carey Price makes a kick save, he can’t just let his leg continue until it reaches the end of its motion, as Roloson could with his glove: he has to slow his leg down in a hurry and push himself back into position. This slowing and readjustment requires activating antagonist muscles (muscles with the opposite action to the “agonist” muscles; for example, the hamstrings are antagonists to the quadriceps) in a coordinated fashion, and adds to the energy demand of the save. Dr. Syme likens it to holding a dumbbell in hand and trying to retrace the path of an Etch-A-Sketch drawing: it takes a lot of energy to move a load around a tightly defined path.
Unfortunately, it’s not a simple matter of making a fast movement, for a couple of reasons, but in order to get to them, we’ll need to take a step back and look at some fundamentals of muscle physiology.
There are two basic kinds of muscle fibre: Type I, or slow-twitch, and Type II, or fast-twitch. Remembering what was said above about speed and force generation, we can say that Type I fibres are primarily useful for generating force but not quick movements, while Type II fibres are for quick movements and force generation; these are the ones we rely on for really fast, powerful movements. Slow-twitch fibres generate their energy mostly through oxygen-consuming aerobic processes, which deliver a steady stream of chemical energy in the form of adenosine triphosphate (ATP) which reduces their susceptibility to fatigue, while fast-twitch fibres generate their energy through glycogen-consuming anaerobic processes, which generate ATP in short but large bursts1, which make them much more vulnerable to fatigue. You’d think at first glance that, because the Type II fibres don’t directly consume oxygen, that you’d be less out of breath after using them, but the glycolytic processes that generate the fibre’s energy come at a cost, generating several unwanted by-products, including lactate and acid. You know that “stitch” you get in your side when you run for a long time? That’s how you know you’ve gone into anaerobic territory. Anyway, in order to get rid of those products, you need… oxygen! So in the end, you still wind up breathing heavily. It makes sense, if you think back to the gym again: when you’re lifting that heavy weight, you may only lift it, say, six times, instead of lifting a light one ten or twelve times, but you still wind up sucking wind pretty badly.
So now we’ve established that by using glycolytic fast-twitch fibres, goalies wind up breathing heavily anyway, but what about “not simply making a fast movement?” Well, muscle fibres are activated, or recruited, in a specific order with increasing demands for power. Smaller motor units — collections of muscle fibres activated by a single alpha motor neuron — of slow-twitch fibres are activated first when the demands for power are low, because of their size and fatigue resistance; only after that, when we require more power, are the fast-twitch fibres activated. So in order to make that fast movement, a goalie has to be “set”: they need to tense up to a degree, co-activating their slow-twitch fibres so that they can more readily recruit their fast-twitch fibres when the time comes. For example, hold your arm out limply beside you and try to flick your hand out at something; now, try tensing the muscles in your arm then flicking your hand out to the same point. It should be faster, because your slow-twitch fibres are already recruited, so there’s already tension in the muscles, allowing you to get right to the quick movement. Order of recruitment is an important consideration, not only because it affects reaction time, but because it affects energy consumption: activating those slow-twitch fibres does consume energy faster than standing relaxed, and require greater replenishment. As an aside, it may also help explain why goalies who face a lot of shots tend to have higher save percentages than those of similar talent who face very few: not only is there the mental “readiness” element, but there’s also the muscular “readiness” element. Ender supports this notion from his own experience by saying, “as the muscles ‘cool’ they seem to stretch, so the more time you have between shots, the more it seems that it involves more energy to begin the motion.” Of course, the body would be poorly designed if there weren’t workarounds to the order of recruitment problem: reflex arcs try to deactivate the slow-twitch fibres while activating the fast-twitch ones, to reduce energy consumption and improve speed in cyclical motions, such as running; whether this particular process is relevant to the task at hand is a bit of an open question.
Somewhat related is the idea of stability. Stability on ice is difficult at the best of times, but when you have five hundred kilos of players flying at you, sticks flailing at a loose puck, it becomes imperative. Recall Newton’s third law, stated axiomatically, “to every action there is an equal and opposite reaction.” In order to throw out an arm or a stick for a save, the goalie needs some sort of contact point with enough friction to keep them from sliding away. Thinking of it another way, when in a post-whistle scrum, players need to keep their skate blades pointed in such a way that they don’t push themselves backwards at the same time they push their opponent. (Or thinking of it yet another way, consider the Magic School Bus’s frictionless baseball game.) Anyway, stability starts at this point of contact, usually the skate blades, and works its way up from there. Because stand-up goalies have gone the way of the rover and the two-line offside, where this really comes into play is during those goal-mouth scrums, when a goalie has to hold his ground against the onslaught. If, for example, a keeper has braced himself against a post, in order to keep from being knocked into the net, he’s going to have to activate muscles all the way from his calves, through his “core” muscles, the abdomen and back muscles, to his arms and neck if need be. Of course, during any movement they will need to do this, whether it’s holding off a scrum at the goal mouth, reacting to a shot from the blue line, or just moving around the crease. In any case, because the goaltender is (quite intentionally) not moving very far, and focusing more on force generation, they will be relying on the slow-twitch Type I fibres.
All this brings me to another topic which has to be considered when looking at energy needs: when a muscle is tensed, the blood vessels which supply oxygen and other nutrients can be occluded, causing them to move to anaerobic energy generation much sooner than blood oxygen levels would otherwise suggest. Another action that might cause unneeded anaerobic activity is called the Valsalva manoeuvre, in which one exhales against a closed airway. While it can be useful in certain circumstances to, say, “pop” one’s ears, when performing physical activity, it will cause a spike in blood pressure, followed by a compensatory drop in cardiac output, which eventually sorts itself out over the course of a few seconds. In physical activity, it’s most commonly encountered as a result of poor breathing technique while lifting weights, but it could also occur when playing goal, and trying to fend off crease-crashers.
We’ve now pretty much exhausted the ways a goalie can wear himself out. True, we haven’t discussed the limited skating a goaltender does, but to be honest, there’s not really anything novel to say about it. Instead, I’d like to turn our attention to recovery, which has a couple of different components. First, as previously stated, goalies make extensive use of the glycogen-burning Type II muscle fibre. Glycogen is a polysaccharide (long-chain sugar) form of glucose stored in tissue, particularly muscle tissue, for future use. This glycogen is consumed as a goaltender goes about his job, and after the game, it must be restored. After a good bout of exercise, it can take at least 24 hours to fully restore glycogen levels, depending on the extent of the consumption. If a goalie’s had a busy night, with a lot of shots, a lot of pileups, and even overtime, his glycogen stores are going to be very low; maybe not as low as a marathon runner’s, but a lot lower than the average weight lifter’s. Unfortunately, I was unable to pull up any specific numbers related to this; I can only go off what I can cull from my first-year exercise physiology textbook.
The other factor to consider is tissue damage, particularly muscle damage. The idea here is that, as you make use of various body parts to perform an activity, you cause microscopic stress damage to them in the process. For the most part, this is no big deal, because everyday activities just don’t do enough damage to be relevant: it heals quickly enough not to matter. When you heavily exercise, however, you start to really feel it. Heavy weight lifters, for example, will only do a small number of reps per set, and will wait several days between exercises on a given muscle group, for precisely this reason: too many reps at a submaximal level (i.e. a weight below the one-rep max, or 1-RM) will still cause enough cumulative damage to rupture a tendon or pull a muscle, so the tissue must be given time to regenerate. Of course, causing minor muscle damage is, ironically, the whole point of weight lifting, for without that stimulus, the tissue would never get stronger. Anyway, when a goalie plays, he will put stresses on his muscles, tendons, ligaments, and bones, and will need to recover from them afterward. If he’s working hard enough to exhaust or nearly exhaust his glycogen supply, chances are good that his muscles are going to be pretty shredded, and that he’s going to be a bit stiff in the morning, no matter what shape he’s in. Given that that’s the case, he needs time to heal up, and while no one muscle group has been worn out as much as our theoretical weight-lifter’s, they are all worn out enough that 24 hours’ rest probably isn’t enough, and that going back out there the next day for more than light exercises (i.e. practice) places the keeper at greater risk for injury. I imagine this is why you see so many more goaltender injuries than you used to, particularly groin injuries: the groin muscles are needed to pull the legs together, and are greatly abused by butterfly goalies. The wholesale movement to that style over the last 20 years, combined with the increased intensity and frequency of games since the Original Six era, when goalies played every game but teams travelled overnight by train instead of in the middle of the night by plane, would naturally result in a greater incidence of overuse injury.
From this, it’s clear that there are a number of compelling reasons why a goaltender should’t play in back-to-back games if it can be avoided: fatigue, dehydration, tissue damage, and fuel consumption all cause a player to be less than 100% for at least a day. As Dr. Syme said near the end of our conversation, “they don’t have the fuel in the tank and they’re not in as good of shape as they were the previous day.” As a result, they are far more susceptible to injury and poor play, a risk that coaches often aren’t willing to take.
Special thanks to Dr. Syme, as well as Bruce and Ender, for their contributions to this article.
1 Strictly speaking, there are several subtypes of Type II fibre, which use varying degrees of oxidative and glycolytic processes, and act at correspondingly different speeds, but for the purpose of this article, we’ll consider all the fast-twitch fibres as a single group.
