Most recognize that endurance athletes need both heavy resistance and endurance training (9). Maximal strength and power training have recently gained attention as a potential strategy for increasing endurance performance (5). However, scientists are yet to elucidate the long-term consequences of this strategy. The following will outline why endurance athletes should limit the amount of strength and power training in their programs.
Training specificity (or matching exercise programming to sport activities) undoubtedly produces the greatest performance gains (8). Endurance performance is characterized by sustainment of low intensity, repeated muscle contractions over a specified duration, or distance. In contrast, success during heavy strength and power training is reliant upon maximizing between-set recovery. Thus, the lack of energetic specificity of resistance exercise makes its transferability questionable (9). Perhaps, this is why disagreement exists concerning how heavy and how often it should be performed (9).
A recent review of the literature concluded that concurrent training (the simultaneous training of resistance and endurance exercise) has a positive effect on endurance performance (11). These data should be interpreted with caution though, as they are limited to acute bouts of exercise and do not account for potential long detriments (i.e., overtraining, etc.) (4). The inclusion of heavy strength/power training (whether it comes from simple addition or replacement of endurance training) may lengthen the time needed to recover (7), compromising the ability to perform the requisite endurance training. A comprehensive literature review found strong evidence favoring an 80-to-20 ratio of low-intensity to high-intensity training in maximizing long-term results for endurance athletes (10). Detailed regulation of workload and recovery are therefore critically important when attempting to engage in concurrent training.
Another counterproductive outcome is the potential hypertrophic effects of resistance exercise. Energetic work is mass × acceleration × distance; meaning more body mass requires more physical work. This is clearly problematic for endurance athletes who support their own body mass (i.e., running). Training-induced hypertrophy also increases both the number and size of myofibrils. This is problematic as it reduces the ratio of mitochondria and myofibril (3). Alternatively, mitochondria size and/or quantities (∼50–100%) and relevant enzyme concentrations (∼2.5-fold in elite runners) increase following endurance training (1). The same relative oxygen uptake disperses among more/bigger mitochondria, resulting in an augmented V[Combining Dot Above]O2, increased capacity to use fat as a fuel, and reduced lactate formation (6). This is significant as V[Combining Dot Above]O2max, lactate threshold, and exercise economy are believed to explain >70% of the variance in endurance performance (2).
When taken collectively, maximal strength is undoubtedly important (5,9); however, the potential benefits are not significant enough to out-weigh the potential decrements. Moreover, the dearth of long-term training studies and lack of direct evidence for its benefit should caution coaches against making strength and power training a major portion of an endurance athlete's program. It should account for no more than 30% of total training and be strategically periodized to account for additional stress and requisite recovery.
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2. Di Prampero PE, Atchou G, Brückner JC, Moia C. The energetics of endurance running. Eur J Appl Physiol Occup Physiol 55: 259–266, 1986.
3. Elder GCB, Sutton R, Howald H. Mitochondrial volume density in human skeletal muscle following heavy resistance training. Med Sci Sports Exerc 11: 164–166, 1979.
4. Halson SL, Jeukendrup AE. Does overtraining exist? Sports Med 34: 967–981, 2004.
5. Hoff J, Gran A, Helgerud J. Maximal strength training improves aerobic endurance performance. Scand J Med Sci Spor 12: 288–295, 2002.
6. Holloszy JO, Coyle EF. Adaptations of skeletal muscle to endurance exercise and their metabolic consequences. J Appl Physiol 56: 831–838, 1984.
7. Kraemer WJ, Ratamess NA. Fundamentals of resistance training: Progression and exercise prescription. Med Sci Sports Exerc 36: 674–688, 2004.
8. Morrissey MC, Harman EA, Johnson MJ. Resistance training modes: Specificity and effectiveness. Med Sci Sports Exerc 27: 648–660, 1995.
9. Rønnestad BR, Mujika I. Optimizing strength training for running and cycling endurance performance: A review. Scand J Med Sci Spor 2013. doi: 10.1111/sms.12104. Epub ahead of print.
10. Seiler S. What is best practice for training intensity and duration distribution in endurance athletes. Int J Sports Physiol Perform 5: 276–291, 2010.
11. Yamamoto LM, Lopez RM, Klau JF, Casa DJ, Kraemer WJ, Maresh CM. The effects of resistance training on endurance distance running performance among highly trained runners: A systematic review. J Strength Cond Res 22: 2036–2044, 2008.
1. Hickson RC, Dvorak BA, Gorostiaga EM, Kurowski TT, Foster C. Potential for strength and endurance training to amplify endurance performance. J Appl Physiol 65: 2285–2290, 1988.
2. Hickson RC, Rosenkoetter MA, Brown MM. Strength training effects on aerobic power and short-term endurance. Med Sci Sports Exerc 12: 336–339, 1980.
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One determinant of sport performance is the ability to appropriately and effectively exert force into the ground (e.g., running) or an apparatus (e.g., cycling) (6). When all other factors are equal, the athlete with a greater ability to exert force will perform the best, as they will cover more distance per muscle action. Therefore, even endurance athletes benefit from increases in force production. Yet surprisingly, the importance of strength and power training in these sports remains challenged. The following will outline why endurance athletes should include strength and power training in their exercise programs.
Traditional teachings are that strength training has little to no effect on cardiac output, V[Combining Dot Above]O2max, heart rate, and arterial mixed venous O2 difference during submaximal exercise (2). However, improvements in movement efficiency are well documented. The addition of strength training to the endurance program of trained cyclists and runners has improved cycling time to exhaustion and 10k running time by ∼44 seconds (1). Improvements in time to exhaustion (2,4) are probably a function of improved running economy (3,4). This is particularly evident in female endurance athletes (4). These increases in movement efficiency may be due to alterations at both the neurological and muscular levels.
Strength training improves motor recruitment patterns, which lowers energy expenditure at any specific submaximal intensity because fewer motor units (and therefore muscles) are activated. Any adaptation that allows an athlete to use less energy at a given speed will decrease the oxygen requirement and should therefore increase athletic performance. Moreover, less muscular contraction leads to less blood flow restriction, which allows greater delivery of fuels and removal of waste products. High-intensity power training (such as plyometrics) offers extra benefits, as it enhances efficiency of elastic energy by increasing musculotendinous stiffness (a measure of how readily tissue reforms after being stretched, compressed, or twisted) (7). This shifts energy production from active (muscular contraction) to passive (elastic rebound) sources.
However, the addition of strength/power training should be done with caution as an estimated 10% of endurance athletes are already overtrained (8). Coaches need to be aware of proper periodization principles and specifically control volume and frequency throughout the macrocycle to reduce this risk. The addition of strength and power training should be countered with the subtraction of some endurance training. For example, replacing nearly 1/3 of endurance volume with explosive strength training has improved leg strength, speed, power, anaerobic capacity, running economy, and most importantly 5k running time (5).
In summary, strength and power training has many benefits for endurance athletes, including improved force output, musculotendinous stiffness and elastic energy efficiency, running economy, and race performance. Intense strength training may indeed increase the risk of injury, but proper monitoring of program design and exercise technique should mitigate this potential harm.