Sami Kaartinen is a former professional ice hockey player (1998–2015), a doctoral student at the University of Eastern Finland (Sports and Exercise Medicine), and an S&C coach at KalPa Hockey (an elite league in Finland), where he is also in charge of skating coaching. Sami is the co-founder and chairman of Pro Prospect, which offers services to optimize the performance of individual athletes, mainly ice hockey players. He is studying skating biomechanics to offer tools to players and knowledge to coaches to help them improve their roles.
Sami has worked with all levels of hockey players, from very young beginners and junior World Championship athletes to Olympic athletes and professional hockey players in top European leagues and the NHL, helping them become better athletes and skaters. He has also had the opportunity to share his skating knowledge with coaches all over Europe.
Freelap USA: Your academic research has focused on ice skating biomechanics. Can you explain some of the major biomechanical differences between faster and slower skaters?
Sami Kaartinen: When talking about fast skaters, I like to divide them based on players with a good ability to accelerate and/or players with high maximal velocity. If you are good at accelerating, it doesn’t automatically mean you have a high maximal velocity or vice versa. Based on my own and previous studies of skating in ice hockey, it seems that there are kinematic elements that increase acceleration rates and maximal skating speeds.
The available knowledge on skating acceleration shows that “running” types of acceleration techniques would be the most efficient way to accelerate in ice hockey—meaning that faster skaters seem to have higher striding rates and shorter contact times (no gliding phase during the skating cycle), with sufficient hip external rotation to offer proper grip on the ice. To support previous components of “running start” acceleration, a higher center of mass (COM) has been reported during first steps. The players with higher acceleration rates have also reported a larger range of motion (ROM) of the hip joint. From my own experience, movement of the hip is one of the key elements driving acceleration.
I often see players having slow hip flexion, which limits:
- The amount of hip flexion during the recovery phase, causing too much hip flexion during initial ice contact and thus negatively affecting fast force production (“kicking” the ice, as I describe the phenomenon).
- There is some evidence that significant forward lean and skate placement straight under the hip, rather than in front of the body, are beneficial for a higher rate of acceleration.
When it comes to the maximal skating phase, greater knee flexion and ROM, together with sufficient hip adduction in the recovery phase, have been observed from the faster skaters. It has also been reported that faster skaters flex their hips more rapidly during the recovery phase. To support this finding, I found in my own study that lower muscle activity of the gluteus maximus (antagonist of the hip flexors) predicts higher skating speed. Furthermore, greater external rotation of the lower limb, together with high extension and abduction velocity, have also been reported to be favorable elements for achieving higher maximal skating speed.
In summary, I would say that during the first 3–4 steps (acceleration), the skate should not glide at all during the ice contact, while during initial ice contact, the lower limb should be significantly extended and contact time fairly short. During the maximal skating phase, great ROM of the hip, knee, and ankle with a quick recovery phase are the basic elements behind greater maximal skating speed.
Freelap USA: When designing an S&C program for a hockey player, what are the key areas coaches should focus on to help improve skating speed?
Sami Kaartinen: Because I am deeply interested in the skating side of ice hockey, my S&C philosophy is based on that. Therefore, I see knowledge of skating biomechanics as the first step—skating might not be a movement the human body was made for. Skating is fast motion and includes movement in all planes (sagittal, frontal, and transversal), in maximal ROM, over a very thin skate blade, on a surface where minimal friction exists. Therefore, it is very important to understand the basics of skating biomechanics.
Even though skating includes different types of speed (e.g., reaction times, stops, and starts) with different kinds of skating techniques (crossovers, backward skating, turns, pivots, etc.), maximal forward skating speed is the simplest and the most analyzed speed in ice hockey. One forward skating stride (or cycle) is already quite a complicated movement pattern that sets high demands on the neuromuscular system.
I want to explain how I see the forward skating stride during the maximal skating phase and which elements and phases are involved when discussing skating speed. The initial part of the propulsion phase, called the gliding phase, is where the most joint flexion of the lower limb joints occurs (“deepest position”) during the skating cycle. During the gliding phase, most muscles of the gliding leg seem to work isometrically (vertical force production) to hold the proper skating position and steer the movement (straight forward versus Z skating) created by opposite limb extension. From these quite deep joint angles, extension of the limb begins, and a lot of power needs to be produced horizontally.
Based on relevant research, it seems that ROM of the lower limb is the main factor behind higher maximal skating speed. Consequently, it is important that an S&C program includes exercises that support force production from quite deep joint angles to the complete extension of the limb. Even though maximal extension velocity is essential, the contact time in skating is quite long (0.35 seconds) compared to sprinting (0.1–0.15 seconds), which coaches should also take into account when deciding on exercises and their intensity.It is important that an S&C program for an ice hockey player includes exercises that support force production from quite deep joint angles to the complete extension of the limb. Click To Tweet
Following powerful extension and abduction (concentric contraction), the player should have suitable capacity to stop the extension motion with eccentric muscle force of the lower limb flexors and adductor muscles. This is the part of the skating cycle where I see a lot of problems and limitations and which causes a lot of injuries to the hip/groin area. A lack of eccentric contraction force in the flexors and adductors makes it very difficult to stop the extension/adduction quickly without limiting the ROM of the extension. Just based on my own experience, I would recommend adding two lower limb flexor exercises per one extension exercise in most cases. In contrast, to return the skate back under the body, extremely fast flexion of the lower limb (concentric work of the flexors and adductors) is a vital element. This enables a new propulsion phase to start as soon as possible.
Of course, there also have to be physiological changes to improve skating speed, but as it is not my core knowledge, I’ll keep this part shorter. In general, increasing speed in ice hockey is based on the same exercise physiology facts as in other sports, where increased muscle force production with enhanced neural drive makes players move faster. Analysis should be done to establish this rate of force development (RFD). I prefer RFD analysis in sport-specific circumstances (on the ice in ice hockey), and there are already methods that could be used to make such analysis on the ice. Of course, off-ice analysis is very useful as well.
Depending on RFD analysis, a decision can be to focus on force production or/and neural drive parts. It should also be decided whether the main target is to develop skating acceleration or maximal skating speed because force-time characteristics are different (0.25 seconds versus 0.35 seconds). Based on these facts, coaches can decide which methods, exercises, intensity, periodization, etc., would work the best.
Freelap USA: In your research, you found that the recovery phase played an important role in achieving a faster skating speed. How would you go about training and improving this quality off-ice?
Sami Kaartinen: I like to say that the recovery phase is a totally underrated and insufficiently focused part of the skating cycle—hence, including significant elements to increase skating speed. It can make a huge difference between skaters since the recovery phase covers approximately 40% of the skating cycle duration. If a player can execute it well, it significantly impacts their skating speed; in contrast, it could limit their skating speed and break their skating rhythm when done poorly. There are numerous ways a poor recovery phase disturbs skating (e.g., short ROM, improper skate position, duration of the phase is too long) and limits skating speed.The recovery phrase is a totally underrated and insufficiently focused part of the skating cycle—hence, including significant elements to increase skating speed. Click To Tweet
The recovery phase includes two main points:
- The “change of direction” point, where the direction of the motion should be changed as fast as possible. To be able to execute this phase efficiently, the lower limb flexor muscles need to produce a lot of eccentric force. The first physiological thing that could limit performance is the excessive imbalance between lower limb extensor/abductor muscles, concentric force production, and eccentric force production of the flexor/adductor muscles. To minimize the imbalance, many specific exercises for lower limb flexors should be done because most “traditional” strength exercises don’t offer the needed load for this motion (two flexion per one extension).
Assisted band exercises work well here—in these, the concentric phase (flexion) is done against the band (as quickly as possible with maximal ROM). During the eccentric phase (extension), the rubber band is pulled by other players to create more resistance during leg extension (eccentric force). Similar results could also be reached with flywheel devices.
- Another important action during the recovery phase is quick hip flexion. I have used “overspeed” methods and exercises to improve this phase. The principle behind the method is to create circumstances where the flexion movement is executed faster than it could be done voluntarily. Different exercises with Bosu balls or other equipment that can create a bounce effect are suitable, including an exercise where an athlete “kicks” the Bosu (which is set on the floor behind the athlete), and the Bosu flings the leg to flexion motion.
Freelap USA: There seems to be a debate among hockey strength coaches on the merits of strength training on one versus two legs, for example, rear foot elevated split squats versus barbell back squats. What are your thoughts on lower-body strength development for hockey players as it relates to skating speed?
Sami Kaartinen: I think both are useful, and it is not an “either/or” thing. In all cases, regardless of the exercise, good technique is the first target, and we, as coaches, should choose the exercises that the athlete can execute with good technique. I also think it’s more what we want to achieve from the exercises than which exercise we use.
Concerning unilateral versus bilateral exercises, more demands on the synergist muscles are needed to control the motion in unilateral exercises. In my opinion, it is easier to create more exercise variations and aim the exercise more specifically to support skating when utilizing unilateral exercises. I also prefer to use unilateral exercises when less overall physical load exists. Bilateral exercise might work better in heavy resistance training during the hockey season to avoid overload of the stabilizer muscles and reduce the risk of injuries. Of course, it is not so simple, but to address the topic, such a guideline could work.
I also like to use unilateral exercises more regularly in all types of strength training when a player has achieved a decent strength level, when they have sufficient ability to control unilateral exercises (fast motion or heavy load), and/or when there are clear target muscle groups (weak link) that should especially be improved. I also prefer exercises where the force production is clearly horizontal.
To work horizontally, all lower limb joints are involved to produce a motion. Both rear foot elevated split squats and barbell back squats (vertical direction movements) activate the movement of the ankle joint a little. My own experience is that the ankle joint is very often the weak link (strength or mobility of the ankle); thus, exercises that offer horizontal force production are recommended.
Bilateral exercises quite often produce linear motion, but as mentioned earlier, with leg extension during the forward skating stride, external rotation exists (demands of the lower limb abductors and other stabilizer muscles) to offer the proper grip on the ice, making such exercises also necessary. Without suitable support from the stabilizer muscles, the force production of the quadriceps and glutes is not fully delivered to the ice; thus, optimal performance will not be achieved.
To summarize my answer, both unilateral and bilateral exercises are helpful in developing strength capacity. In addition, a very useful tool to develop skating-specific strength is to do it on the ice. When possible, I always prefer to use the method of skating against resistance (e.g., a band) on the ice. I have found it also a critical part of an on-ice rehab program after injuries to get players to return to the games in optimal shape.
Freelap USA: Many S&C coaches implement sprint training in their athletes’ off-ice programs. Can you explain the biomechanical similarities and/or differences between the skating stride and linear sprinting? Moreover, do you think sprint training can have a beneficial impact on on-ice skating performance?
Sami Kaartinen: I think—and studies have shown—that if you are a fast runner, you are likely also a fast skater. But improving skating speed by running may not be straightforward. The reason comes down to the differences in muscle actions and neural control required by the two actions.
Ground contact time (GCT) during sprinting acceleration is about 0.18 seconds, and it decreases close to 0.1 seconds or less during the subsequent steps. Meanwhile, in ice hockey, the contact time moves in the opposite direction, starting from 0.25 seconds while accelerating and being about 0.35 seconds at the maximal skating phase. The short contact time in running allows for the storage and utilization of elastic energy and using that energy to power the running. In contrast, stride GCT lasts longer during ice hockey, which limits the potential of elastic energy utilization and requires power to be generated with concentric muscle contraction. These differences are reflected in the effective training strategies that, in running, include more plyometric training, and in skating, include more exercises to improve concentric force generation ability.
There are also noticeable differences in kinematics while sprinting and skating. First, the lower limb range of motion during ground contact is generally significantly greater while skating. Additionally, in skating, the hip and knee ROM increase, going from the acceleration phase to maximal speed skating, whereas in sprinting, the opposite change occurs.
So, to answer the question, I find linear sprinting a valuable method to develop skating speed. But I use short sprints (0–10/15 meters)—basically the phase before the maximal sprinting phase—because short sprints better mimic the maximal skating phase kinematics in shorter GCT as on the ice. To better match the GCT and kinematics seen in skating, I often use either uphill sprints or resisted sprints. These are methods that I have also found very safe for hockey players.To better match the GCT and kinematics seen in skating, I often use either uphill or resisted sprints. These are methods I have also found very safe for hockey players. Click To Tweet
Sprint training is a useful tool to develop skating speed, but it has to be well-designed as part of training, and the purpose of the training needs to be clear. To avoid unnecessary injuries, I would be careful about making ice hockey players run full-speed sprints where maximal sprinting biomechanics occur, as there are more safe methods to use that are more linked to skating performance and biomechanics.
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