Effects of Strength Training on Endurance Performance
May 16, 2012
Column Editor- Bob Kaehler, MSPT, CSCS
By Robert Blaisdell, BS, CSCS
The notion of endurance athletes training for their sport while utilizing non-sport specific resistance training has long been in dispute for its supposed adverse physiological changes and the interference with peak performance in endurance sport endeavors. This school of thought governed the training principles of endurance sport athletes despite developments in periodization and knowledge of specific training applications for endurance sport for quite some time.
The highly trained marathon runner is hardly the ideal “poster-person” for the promotion of body-building in the traditional sense of lifting huge amounts of mass in a sweaty gym, nor is the highly trained body-builder the ideal “poster-person” for the next big regatta’s marketing campaign. Seasoned athletes in each of their respective sport areas know better and would scoff at either of the aforementioned sights. But what a few, and growing number of these seasoned athletes know is that some beneficial cross-over adaptations taking place when one implements training strategies that utilize some formerly “taboo” methods. Both strength and endurance training methods can be valuable to one’s health and fitness levels when implemented safely and scientifically, but a combination of the two can be quite advantageous for an athlete, especially the endurance sport athlete. Keep in mind that there are specific training protocols which should be followed for optimal results and such aspects will be discussed later in this article. It is the intent of this article to promote the use of strength training as a practical and advisable means to utilize in the training for endurance sport. With that being said, this paper will attempt to discuss and explain the benefits of strength training for endurance performance through describing the physiological adaptations to strength and endurance training programs, the effects of strength training on endurance performance in several endurance sports, and how to effectively implement a strength training protocol in an individual’s endurance sport training program.
Training specificity does play a key role in the individual physiological training adaptations of a strength training and endurance training program. The characteristic adaptations of a resistive strength training program defined by high loads and low rep ranges are an increase in muscle hypertrophy, which in turn translates to an increase in muscle cross-sectional area. This increase in cross-sectional area is representative of the internal physiology of increases in muscular protein content, fiber size, and possibly fiber number [1]. The increased muscle fiber size elicits an increase in muscle force production, which is characterized by increases in muscle strength, power- peak and short-term, as well as increased time to exhaustion at higher intensity sub-maximal levels. Resistive strength training adaptations elicit little to no change in activities of phosphagen, glycolytic, and oxidative enzymes [1]. Resistive strength training will, at best, maintain capillary density, which translates to the rate of O2 diffusion/ delivery remaining the same as the level it was prior to the resistive strength training program. Resistive strength training produces increases in trained muscle of glycogen content. Finally, resistive strength training programs have shown to increase an individuals VO2 max ~ 3% [1], but this increase is only representative of untrained individuals and not representative of normal results, which show no increase in VO2 max. Most research also suggests that resistive strength training program adaptations are similar between genders [2].
The characteristic adaptations of an endurance training program defined by low loads and high repetition ranges are an altering of size and ratio of type IIb muscle fibers, and an inherent decrease in muscle cross-sectional area. The decrease of type IIb fibers is characterized by a shift to type IIa. Endurance training, unlike resistive strength training, shows a decrease in the activity of glycolytic enzymes. Endurance training programs also show an increase in intramuscular substrate stores and oxidative enzyme activity [1]. An increase in capillary and mitochondrial density is representative of endurance training and is a good description of the “aerobic” aspect of endurance training. With endurance training there is a marked decrease in myofiber contractile properties which translates to a decrease in force generation capacity of type I and IIa fibers [1], but this decreased force production, especially of the type IIa fibers could elicit the increase in fiber efficiency that endurance athletes are so fond of. The aforementioned decrease in muscle cross-sectional area also has its advantages. This decrease in cross-sectional area translates to a decreased distance that O2 diffuses, therefore decreasing O2 delivery time. The collective adaptations of endurance training programs are increase in VO2 max, lactate threshold, and endurance capacity [1].
To summarize the physiological adaptations of resistive strength training and endurance training, one could conclude that both induce one common muscular adaptation; they both transform type IIb fibers into IIa fibers [1]. The resultant transformation has opposite changes in fiber size and contractile properties [1]. Each of these changes was brought about by a specifically designed training program, periodizationally designed to elicit the most results in ones training for each respective sport.
While there are numerous research studies outlining the positive effects of a resistive strength training program on endurance performance, this article will take a closer look at a few select studies and highlight their respective findings. The endurance performances that were examined in the respective research articles were running performance, cycling performance, rowing performance, and finally swimming performance.
The research presently available that evaluates running performance after a resistive strength training program protocol does so for untrained and moderately trained populations. The increases an individual would acquire from a resistive strength training program would translate to increased strength and therefore anaerobic power, which could help a running performance during increases in speed, hills, and sprint finishes. According to the reports and those evaluated by other reports, higher anaerobic power can be a key determinant when comparing cross-country runners with a similar VO2 max. Studies that have utilized untrained as well as moderately trained runners, report increases in leg strength following a resistive strength training program on average 25% to 40% greater than the values recorded pre-study, and a 10% to 13% increase in short term treadmill performance, although the protocol for either testing procedure was not reported. Both of these improvements in performance came about with no reported increase in VO2 max. According to Tanaka and Swenson, these increases in performance may be from increases in fiber size which allows individuals to exercise longer at each respective sub-maximal intensity by reducing force contribution required from each active myofiber and thus using less of them to sustain a similar work load prior to the resistive strength training program. A stronger type I fiber may allow resistance trained individuals to delay recruitment of less efficient type II fibers for running performance [1]. In summary of the research available for resistive strength training programs on running performance, it can be noted that resistive strength training programs added to an endurance running program may decrease the degree of activation per motor unit and muscle fiber, therefore decreasing the number of motor units and muscle fibers needed for running performance [1].
The research that applies a resistive strength training program to the sport of cycling is quite numerous and this paper will discuss a few different studies that utilize various training methods of resistive strength training. Similar to the demands of running, cycling performance is enhanced by the ability of utilizing anaerobic and short term power for attacks, climbing, and sprinting throughout competitive cycling races. The results of resistive strength training programs administered for the sole purpose of improved cycling performance have supported the hypothesis that these resistive strength programs do elicit favorable gains in cycling performance. The overall impact of resistive strength training on cycling performance shows that resistive strength training programs increase Wingate anaerobic power outputs from 6% to 17%, leg muscular strength from 3% to 35%, and short term performance by ~29% in the untrained individual [1]. The time to exhaustion increased 20% at a workload intensity of 80% VO2 max in trained individuals, and 33% at a workload intensity of 75% in untrained individuals [1]. The latter corresponds to a 12% increase in blood lactate threshold level, a key determinant in endurance performance. These improvements in cycling performance are due in part to the same physiological adaptations found in the aforementioned running performance research which states that increases in performance may be from increases fiber size which allows individuals to exercise longer at each respective sub-maximal intensity by reducing force contribution required from each active myofiber and thus using less of them to sustain a similar work load prior to the resistive strength training program. A stronger type I fiber may allow resistance trained individuals to delay recruitment of less efficient type II fibers for running performance [1].
A study which examined the gains in sprint and endurance cycling performance through explosive resistive and high intensity training programs during a competitive cycling phase in highly trained cyclists concluded that the well trained cyclists in the study had significantly major gains in cycling performance through improved exercise efficiency and increased anaerobic threshold levels [3]. The conclusion of this study recommends that replacing a portion of the competitive training phase with high intensity-explosive resistive strength training protocols will elicit major gains in sprint and endurance performance. The reasoning behind this recommendation is that the neural activation adaptations possibly contributed to the increase in sprint performance, and that the explosive type of resistive strength training led to an increase in the firing frequency of motor units which then increased muscle peak force and rate of force development [3].
The common theme among the studies is that the resistive strength training programs were beneficial to improvements in cycling performance and are further evidenced by a similar study by Izquierdo et al., which examined the effects of strength training on sub-maximal and maximal endurance performance in middle-aged and older men. This study reported significant improvement in both areas in the first 8 weeks of the 16 program. There were no decreases in performance following the initial 8 weeks, but the subjects did reach a plateau in improvement. This initial improvement was reportedly linked to an increase in blood lactate threshold [6].
The research utilized for this article evaluates rowing performance after a resistive strength training program in trained and untrained female collegiate rowers. The study conducted by Ebben et al., specifically looked at the effects of high-load versus high-repetition resistive strength training programs on endurance performance of female rowers. The nature of successful rowing performance requires a high level of aerobic capacity as well as muscular strength [2]. A varsity and freshman women’s crew teams were both involved in the study and both groups were reported to have improved their rowing performances following the study. The difference in the modalities of the resistive strength training is where the variation lies for each respective group. The more highly trained varsity rowers showed that the high load resistive strength training program is what elicited improvements in rowing performance as compared to the less trained freshman rowers, who responded more favorably with the high-repetition resistive strength training program. The findings are consistent with a pre-existing hypothesis that pre-training status dictates the amount of potential adaptation [2]. The research concludes that “regardless of whether or not VO2 max changed with training, peak VO2 did increase with the concurrent training protocol” [2]. This improvement of peak VO2 can be associated with the rowing performance.
The last endurance sport this paper will discuss is swimming. The results of recent studies examining the effectiveness of strength training programs on swim performance show contradictory results of those of the aforementioned running, cycling, and rowing studies. The swim studies conducted utilized both untrained and trained swimmers but despite increases in upper body muscular strength of ~30% through combined swim and resistive strength training programs, there were no related increases in swim performance by way of faster times or decreases in blood lactate threshold levels during those specific splits. This contradiction in endurance improvements is due to the highly technical stroke mechanics of swim performances and their related dynamic strength requirements [1]. What did invoke improvements in swim performance was a combination of endurance swim training and in-water, swim-movement specific resistance training programs. These in-water, swim-movement specific resistance protocols consisted of swimming flumes, biokinetic swimming bench training, and in-water resistance devices [1].
When applying a strength training program to elicit positive changes in endurance performance one must carefully perform a needs analysis, biomechanical analysis, as well as examine the periodization of the yearly training program. All of these variables will help to decide which is the proper resistive strength training program protocol to utilize. The nature of endurance sports, like most other sports, is to have an in-season and an off-season. The goal of each respective phase is very different, as training during these phases should be as well. During the off-season, the endurance competitor is engaging in fairly low intensity for long durations, whereas during the in-season, the competitor engages in races of varying importance and trains at higher intensities for shorter durations [5]. The resistive strength training program should follow suit, and consist of lower intensity, high volume training protocol during the off-season and consist of higher intensity, low volume training during the in-season phase of the periodized year [5]. Utilizing specific resistive strength training exercises with movement patterns to coincide with the movement patterns of your endurance sport can be beneficial to the overall improvement and effectiveness of a resistive strength training program. Using these movement specific exercises can also aide in reduction of muscle imbalances which could plague the high repetition endurance athlete.
It was the intent of this article to promote the use of strength training as a practical and advisable means to utilize in the training for endurance sport. This article discussed and explained the physiological adaptations of both resistive strength and endurance training programs, the effects and subsequent benefits that these physiological adaptations had in specific endurance sports and described how to effectively implement a strength training protocol in an individual’s endurance sport training program, which should be followed for optimal results. As this article has shown the evidence to support the argument that resistive strength training is a valuable and worthwhile training method for endurance sport performance, this type of concurrent training will not only produce increases in performance but also decreased risk of injury due to muscle imbalance and overuse syndromes.
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References
1. Tanaka, H., Swenson, T. (1998). Impact of resistance training on endurance performance: a new form of cross-training? Sports Med, 25 (3): 191-200.
2. Ebben, W. P., Kindler, A.G., Chirdon, K. A., Jenkins, N. C., Polichnowski, A. J., Ng, A. V. (2004). The effect of high-load vs. high-repition training on endurance performance. Journal of Strength and Conditioning Research, 18 (3): 513-517.
3. Paton, C. D., Hopkins, W. G. (2005). Combining explosive and high-resistance training improves performance in competitive cyclists. Journal of Strength and Conditioning Research, 19 (4): 826-830.
4. Bastiaans, J. J., van Diemen, A.B.J.P., Veneberg, T., Jeukendrup, A.E. (2001). The effects of replacing a portion of endurance training by explosive strength training on performance in trained cyclists. European Journal of Applied Physiology, 86: 79-84.
5. Erickson, T. M. (2005). The benefits of strength training for endurance athletes. NSCA’s Performance Training Journal, 4 (2): 13- 17.
6. Izquierdo, M., Hakkinen, K., Ibanez, J., Anton, A., Garrues, M., Ruesta, M., Gorostiaga E. M. (2003). Effects of strength training on submaximal and maximal endurance performance capacity in middle-aged and older men. Journal of Strength and Conditioning Research, 17 (1): 129-139.
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