A unique combination of speed, agility, strength, and power sets professional athletes apart from the rest. Are these attributes genetic, or do they result from hard work and dedication? In science, answers are rarely black and white and this question is no different. It is a complex interplay of genetics and training, which sets off a cascade of physiological and anatomical mechanisms, that produces our professional athletes. These mechanisms are wide in their scope and intricate in their complexity. Therefore, this article focuses on explaining muscle fiber properties in the context of basketball related performance. It also presents some training principles to help the athlete improve his or her performance.
Muscles and Contractions
When we decide to move a part of our body, the brain sends a signal through the nervous system. The signal, carried by motor neurons, then travels to the muscles required to perform the desired action, causing contraction and movement. Despite this apparent simplicity, much more actually occurs, making this process quite complex.
The neuromuscular junction is the location where the signal from the nervous system meets the muscular tissue. Motor neurons branch as they approach muscles to the point where only one individual branch innervates a muscle fiber (Seeley et al. 2006). There is a small gap between the neuron and the fiber called the synaptic cleft. The signal carried by the neuron causes a release of particles called neurotransmitters into the synaptic cleft, signaling the muscle fiber to fire (Seeley et al. 2006).
On the molecular scale, muscle contraction is a result of what is known as the sliding filament theory (Huxley and Hanson 1954, Huxley and Niedergerke 1954). Briefly, each muscle fiber houses a sarcomere. Inside the sarcomere, a thick filament composed of myosin and a thin filament composed of actin reside. Upon neurotransmitter signaling, the thick myosin protein uses a ratchet motion to move the actin protein and cause contraction (Seeley et al. 2006, Plowman and Smith 2008). A more in-depth explanation of the sliding filament theory and muscle contraction is given in another article: 95 miles per hour: Performance Physiology of Pitchers.
Muscle fibers are categorized into two groups: slow-twitch (ST) and fast-twitch (FT). For the purposes of this article, we will consider the most common forms of these two fibers found in the literature. Type I fibers are ST fibers and type II fibers are FT. There are two classifications of type II fibers called type IIa and type IIx (Baechle and Earle 2008). A surface level difference between fast- and slow-twitch fibers is the amount of blood supplied to the muscle. Type I fibers have a well established blood supply and stain red during histochemical staining while type II fibers have a less developed blood supply and stain white (Zierath and Hawley 2004). This can be seen in a chicken or turkey where breast meat is white (fast-twitch) and the legs and thighs are dark (slow-twitch).
Type I fibers have a small diameter with a large population of mitochondria, giving them a high aerobic capacity (Baechle and Earle 2008). This aerobic capacity directly relates to the slow relaxation and twitch times, but also predisposes the muscle to fatigue slowly (Plowman and Smith 2008). In physiology, structure always determines function. The aforementioned structural characteristics give good evidence to say that type I fibers are used primarily in weak or moderately strong contractions that must take place over extended periods of time or that occur in a repetitive manner (MacIntosh et al. 2006).
Type IIx fibers are on the opposite end of the spectrum from ST fibers. These fibers have a large diameter with a low density of mitochondria, thus, their aerobic capacity is low but their ability to function in the absence of oxygen is extremely high (Baechle and Earle 2008). In stark contrast to ST fibers, type IIx fibers contract fast and hard but fatigue very easily (Plowman and Smith 2008).
In between type I and type IIx fibers are type IIa fibers. These fibers are essentially a mix of the properties of the two extremes. Their diameters could be considered intermediate in size and the density of mitochondria is at moderate levels as well (Baechle and Earle 2008). They have the ability to work in oxygen rich and oxygen deprived situations, meaning they can function in long duration activities and those of shorter, more intense, effort as well (Plowman and Smith 2008).
So, does this information mean that when you want to go fast your body activates FT muscles and when you want to go slow it uses ST? The answer to this is no: the body evokes a specific pipeline of recruitment to carry out all skeletal muscle tasks (MacIntosh et al. 2006). The body starts with type I muscles, and then evokes type IIa in addition to type I as the need for contraction increases. Finally, type IIx fibers can be recruited if the need for stronger contraction continues to grow (Vollestad et al. 1984, 1992, Vollestad and Blom 1985, Zajac and Faden 1985). However, in specific fast or sudden corrective movements, the body does allow for type II units to be selectively activated (MacIntosh et al. 2006). This phenomenon can be clearly seen in many reflexive actions.
The body’s specific protocol for muscle recruitment has implications for athletes. If there are more ST muscles, it will take longer for the force of contraction to grow large enough to recruit more FT fibers. Conversely, if there are fewer ST fibers, then type II fibers may be recruited sooner in those individuals. Therefore, we will next look at the distribution of fibers within individuals and athletes.
The distribution of fiber types can vary from one person to another in the same group (Saltin et al. 1977) and depends on the genetics of individuals (Simoneau and Bouchard 1995). However, scientists do have a general idea of locations in which each fiber type is in high density. Muscles that contribute to sustained postural activity tend to have the highest amount of ST fibers (Plowman and Smith 2008), whereas the limbs contain more FT fibers (Seeley et al. 2006). The percent of ST fibers in sprinters has been shown to be more than half that of endurance cyclists (Fox et al. 1993). Furthermore, it has been shown that these differences can be attributed, to a degree, to sport specific exercise and training (Saltin et al. 1977). What these data indicate is part of our distribution of fiber types is due to genetics, and some is due to sport-specific training.
Basketball’s Physiological Requirements
Understanding the training needs for basketball requires more than just knowing about muscle fiber types. It requires a thorough knowledge of the systems needed during competition. Therefore, this section will briefly discuss the muscles, energy systems, and recovery principles that contribute to speed, agility, and power on the basketball court.
The upper body demands of a basketball player are greatly inferior to those of the lower body. For this reason, the focus will be on the lower body only. The buttocks, quadriceps, hamstrings, and calves play the most significant role in speed, agility and power. Core stability has been shown to contribute to running performance (Sato and Mokha 2009), so it must be considered as well.
A study done by McInnes et al. (1995) sought to quantify the physiologic load placed on basketball players, lending insight into training demands for athletes. They found that players change direction on average every 2.0 seconds. Additionally, they did about 105 high-intensity sprints per game, one every 21 seconds, lasting an average of 1.7 seconds. Data indicate glycolysis as the primary energy producer, meaning that anaerobic endurance is required. Furthermore, players had an average heart rate of about 169 beats per minute throughout the game. All these data led the authors to conclude that metabolic and cardiovascular demands are high in basketball players (McInnes et al. 1995).
Fitness and Training
It is important to review the needs and goals of a training program designed around a basketball player. First and foremost, the program must train for FT fiber development in the legs. At the same time, the anaerobic energy system must be trained to ensure stamina and recovery during high intensity bursts. Finally, agility (which is the ability to change direction) needs to be incorporated.
Agility training has been shown to increase muscular response times in the quadriceps and gastrocnemius (calves) (Wojtys et al. 1996). T-drills, lateral movement drills, and balance drills are all components of agility training. The type and variety of agility drills is endless, essentially any drill that incorporates quick movements with changes in direction in 5-15 second intervals will improve agility, build anaerobic endurance, and develop FT fibers.
Plyometric (plyos) and ladder drills are two effective means of increasing quickness and explosiveness through FT fiber development. Plyos are generally very rapid, short distance jumps that occur in 5-20 second sets. Dot drills and four-square setups are the most common. In both, there is a pattern of dots or numbers on the ground in which the athlete uses one or two legs to hop about the pattern in a variety of ways. Speed ladders are similar but all movements move the athlete along the ladder, making these drills less stationary. These two methods are nearly endless in their variety.
Incorporating core training must be done as well. Swiss ball, stabilization, lower back, and hip flexor exercises work together to build the entire core. We have discussed that the stabilizing core muscles are primarily ST fibers, so exercises need to be designed with this in mind. Rapid repetitions are less important here as the body is genetically predisposed to maintain ST fibers in this region (Plowman and Smith 2008). Long duration core stabilization exercises like leg raises and planks should be the focus.
Finally, it is important to work the training protocol around the previously mentioned activity data from McInnes et al. These data tell how to design recovery times between sets and between training sessions. Recovery should never be taken lightly as it is just as important as the actual activity in improving performance.
The principles presented in this article can be applied to a wide range of sports whose demands are similar to those of basketball. It is important to remember that there are limits to everyone’s abilities. Most of us will never get close to the level of Michael Jordan or LeBron James, yet each person does have room to improve in some aspect of their game. The requirements for improvement are simple: hard work and dedication. With these two ideas in mind, it is nearly impossible to produce a training program that does not improve performance.
By: Josh Silvernagel, Graduate Student, Bioengineering, University of Utah
Josh Silvernagel received undergraduate degrees in Exercise Science and Mathematics from Bemidji State University (BSU) in Bemidji, MN. During his undergraduate studies, he was a four year starter in baseball for the BSU Beavers, where he both pitched and played infield. In addition to providing sport specific training for ametuer and professional athletes following school, Josh spent two years coaching the sport at both the collegiate and high school levels. He is currently working on a Ph. D. in Bioengineering at the University of Utah, where he studies cardiac electrophysiology in the CARMA Center. Josh and his wife, Danielle, are recently married.
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