The Physiological Responses to Resistance Training
Will resistance training improve anaerobic performance?
ABSTRACT
The purpose of this literature review is to identify the physiological adaptations, directly resulting from strength training and their effect on anaerobic performance. The inclusion criteria for this review are 1) full-text, peer reviewed journal articles, 2) studies with human subjects and 3) articles published within the last 15 years. The key words searched were resistance training, strength training, anaerobic performance, physiological adaptations and neuromuscular responses.
The main physiological adaptations due to strength training are muscle fiber type conversions (1, 9, 14), an increase in muscle cross-sectional area (CSA) (1, 9), an increase in muscle fiber peak power (1, 11), increased voluntary activation of muscles (4, 6), increased discharge and torque development rates of motor units (4, 6), increased motor unit synchronization (6) and decreases in the co-activation of antagonist-muscles (4, 6). These adaptations work together to improve key factors such as strength and power, both of which are principal indicators of anaerobic performance. Therefore, in conclusion and after a comprehensive review of the literature, there is unanimous support for the proposition that strength training does improve anaerobic performance.
Key Words – Resistance Training, Strength Training, Anaerobic Performance, Physiological Adaptations, Neuromuscular Responses, Hormonal Responses
INTRODUCTION
For as long as sports have been around, people have been trying to find the best training methods to improve performance. This isn’t restricted to team sports or individual efforts and in our society where such an emphasis is put on winning and the performance of athletes, recent research has started to compile on the best methods for improving performance. This review is targeting “anaerobic performance”, as it plays a huge role in many of our sports or athletic tasks and whether or not strength training helps to improve anaerobic performance.
The physiological adaptations experienced as a result of strength training have been split into two categories. The first of which is muscle fiber responses. The muscle fiber responses look at the fiber type conversions experienced from strength training (1, 9, 12), the muscles and muscle fibers cross-sectional area (CSA) (1, 9) and the muscle fiber’s ability to produce peak power (1, 9, 13). The second category is neuromuscular responses, which includes the level of voluntary activation of muscles (4, 6), the discharge and torque development rates of motor units (4, 6), the level of motor unit synchronization (6) and the relationship or “co-activation” between agonist and antagonist muscles (4, 6).
Physiological Adaptations to Strength Training
The physiological adaptations due to strength training can be divided into two groups; Muscle fiber responses (1, 9, 14), neuromuscular adaptations (4, 6).
Muscle Fiber Responses:
The main adaptations found in regards to muscle fibers are fiber type conversions (1, 9,14), an increase in muscle cross-sectional area (10) and an increase in muscle fiber peak power (1, 9). Usually, resistance training by itself doesn’t have a large impact on shifting type I fibers to type II fibers (1, 9), however strength training does result in an upward shift to type IIA muscle fibers (fast twitch) (1, 9, 14) especially when run congruently with sprint training (14). The CSA of a muscle is another key adaptation. The CSA of muscles and muscle fibers increase with strength training (1, 9, 10). This increase in CSA is largest in type IIA muscle fibers (10, 14), which as discussed, have become more numerous since strength training promotes a fiber shift towards type IIA muscle fibers (1, 9, 14). Another very noticeable response to strength training is an increase in peak power produced by muscle fibers (1, 9, 10). This is partially due to the increase in number and CSA of type II muscles fibers, which when compared to type I muscle fibers, are capable of producing 6-10 times the peak power (14). It is also due to an increased shortening velocity of the muscle fibers (9).
Neuromuscular Responses:
There are several very important neuromuscular adaptations that also occur as a direct result from strength training such as the increased voluntary activation of muscles (4, 6), increased discharge and torque development rates of motor units (4, 6), increased motor unit synchronization (6) and a decrease in co-activation of antagonist-muscles (4, 6). These adaptations all contribute to someone being able to produce a higher level of strength and force development with their muscles (4, 6). It has been found that when a person/athlete voluntarily contacts a muscle, they cannot fully activate that muscle (6). Even after performing strength training, people cannot fully activate their muscles voluntarily, but their levels of activation are increased (4, 6). Therefore, the level of muscle activation can be increased and subsequently, the capacity of that muscle is increased. In order to the overcome the increased stimulus of strength training, the subjects motor units are able to fire faster and more powerfully (4, 6), also known as rate coding (4). By increasing the motor units firing rate and rate of torque development, they are able to produce higher levels of muscular force enhancement (4, 6) and muscular strength (6). The next neuromuscular response found after strength training is the increase of motor unit synchronization (4, 6). Motor unit synchronization is the process of numerous motor units simultaneously activating (6) and has been shown to increase with resistance training (6). An increase in motor unit synchronization will result in elevated levels of force development (6). The final major neuromuscular adaptation to strength training is the decrease of co-activation from antagonist muscles (4, 6). As agonist muscles try to move a limb in one direction, they are opposed by antagonist muscles, which are working to move the limb in the opposite direction (6). Although co-activation of agonist and antagonist muscles increases the joint stability and stiffness (4), it is responsible for a decrease in force development (4, 6). Strength training reduces this co-activation (4, 6) and therefore an increase in force production is evident (4, 6).
Effect of Strength Training on Anaerobic Performance
To determine whether strength training has a positive effect, it is important to identify the key factors associated with anaerobic performance. I am emphasizing the ability to create a large amount of force and power over a short distance or period of time.
This review has confirmed that strength training will improve strength (3, 5, 12) and power (2, 11). Improved strength and power are products of neuromuscular responses such as improved rate coding (4, 6) and the decreased co-activation of antagonist muscles (4, 6). Strength training also results in muscle fibers shifting towards type IIA muscle fibers (1, 9, 14), which can produce 6-10 times the peak power of type I fibers (16) and increased CSA (1, 9, 10), which has also been positively correlated with an increased strength and power (11).
CONCLUSION
In conclusion, if you want to improve your anaerobic performance, then strength training is one of the most effective tools you could take advantage of. Strength training results in physiological adaptations to the body, which as discussed can be split into two subgroups; Muscle fiber responses and neuromuscular responses. These adaptations work together to improve key factors such as strength and power, both of which are principal indicators of anaerobic performance. Based on the literature reviewed, there are some practical applications. If you are competing in a sport that relies on elevated anaerobic activity, then strength training will improve your overall athletic performance and reduce the risk of injury.
REFERENCES
1. Andersen, J. L., & Aagaard, P. (2010). Effects of strength training on muscle fiber types and size; consequences for athletes training for high-intensity sport. Scandinavian Journal of Medicine & Science in Sports, 20, 32-38.
2. Chtourou, H., Driss, N., Souissi, S., Gam, A., Chaouachi, A., & Souissi, N. (2012). The effect of strength training at the same time of the day on the diurnal fluctuations of muscular anaerobic performances. Journal of Stength and Conditioning Research, 26(1), 217-225.
3. Comfort, P., Haigh, A., & Matthew, M. (2012). Are changes in maximal squat strength during preseason training reflected in changes in sprint performance in rugby league players? Journal of Stength and Conditioning Research, 26(3), 772-776.
4. Duchateau, J., Semmler, J., & Enoka, R. (2006). Training adaptations in the behavior of human motor units. Journal of Applied Physiology, 101, 1766-1775.
5. Fatouros, I., Kambas, A., Katrabasas, I., Nikolaidis, K., Chatzinikolaou, a., Leontsini, D., et al. (2005). Strength training and detraining effects on muscular strength, anaerobic power, and mobility of inactive older men are intensity dependent. British Journal of Sports Medicine, 39(10), 776-780.
6. Gabriel, D., Kamen, G., & Frost, G. (2006). Neural adaptations to resistive exercise. Sports Medicine, 36(2), 133-149.
7. Ingle, L., Sleap, M., & Tolfrey, K. (2006). The effect of a complex training and detraining programme on selected strength and power variables in early pubertal boys. Journal of Sports Sciences, 24(9), 987-997.
8. Kraemer, W., & Ratamess, N. (2005). Hormonal responses and adaptations to resistance exercise and training. Sports Medicine, 35(4), 339-361.
9. Malisoux, L., Francaux, M., & Theisen, D. (2007). What do single-fiber studies tell us about exercise training? Medicine & Science in Sports & Exercise, 39(7), 1051-1060.
10. Martel, G. F., Roth, S. M., Ivey, F. M., Lemmer, J. T., Tracy, B. L., Hurlbut, D. E., et al. (2006). Age and sex affect human muscle fibre adaptations to heavy-resistance strength training. Experimental Physiology, 91(2), 457-464.
11. Mayhew, J. L., Hancock, K., Rollison, L., Ball, T. E., & Bowen, J. C. (2001). Contributions of strength and body composition to the gender difference in anaerobic power. Journal of Sports Medicine and Physical Fitness, 41(1), 33-38.
12. Minahan, C., & Wood, C. (2007). Strength training improves supramaximal cycling but not anaerobic capacity. European Journal of Applied Physiology, 102(6), 659-666.
13. Ronnestad, B. R., Kvamme, N. H., Sunde, A., & Raastad, T. (2008). Short-term effects of strength and plyometric training on sprint and jump performance in professional soccer players. Journal of Strength and Conditioning Research, 22(3), 773-780.
14. Wilson, J., Loenneke, J., Jo, E., Wilson, G., Zourdos, M., & Kim, J. (2012). The effects of endurance, strength, and power training on muscle fiber type shifting. Journal of Strength and Conditioning Research, 26(6), 1724-1729.
Written by Nevin Mills - The Strength Institute of Western Australia
