Research Review By Dr. Shawn Thistle©

Date Posted:

December 2009

Study Title:

The effects of resistance training on endurance distance running performance among highly trained runners: A systematic review

Authors:

Yamamoto LM, Lopez RM, Klau JF et al.

Author's Affiliations:

Human Performance Laboratory, Department of Kinesiology, University of Connecticut, USA.

Publication Information:

Journal of Strength & Conditioning Research 2008; 22(6): 2036-2044.

Background Information:

Running is extremely common and growing in popularity. Most strength and conditioning professionals can attest that historically, runners are generally hesitant to incorporate resistance training into their programs for fear of inducing physiological or anatomical adaptations that are not conducive to improving running performance. Some fear that adaptations such as muscle hypertrophy or alterations in capillary density or mitochondrial function will fight “against” their endurance training, rather than complement it.

Concurrent resistance and endurance training (referred to in this review as CT or “Concurrent Training”) challenges the notion that improvements in distance/endurance running performance are achieved only through aerobic training. It makes sense (doesn’t it?) that muscular strength and anaerobic power may also be important for increased running performance through neurological and muscular changes, and there exists research to support this (1, 2).

To review, positive muscular adaptations to resistance training include:
  1. increased anaerobic enzyme activity;
  2. increased force production;
  3. increased intramuscular glycogen;
  4. and/or shifts within major fiber type groups
Neural adaptations may include:
  1. improved motor unit recruitment and synchronization;
  2. improved force development rate;
  3. and/or improvements in the stretch-shortening cycle
When combined, these adaptations may enable distance runners to climb hills with more power, or sprint to the finish line (or at other times during a race), both of which should enhance running performance.

Instead of running performance, which may be too general, many CT researchers now focus on running economy (RE), which involves the relation between VO2 and a given running velocity. Practically speaking, improving RE would increase speed over a given distance or increase the distance traveled at a given speed because of decreased oxygen consumption, thus increasing performance.

Resistance training and resultant strength gains may improve RE through several mechanisms:
  1. increased strength can improve mechanical efficiency, muscle coordination, and motor recruitment patterns
  2. greater total body strength may result in advantageous mechanical changes in running style
  3. increased muscular strength and coordination may reduce relative intensity at a given velocity
The literature to date investigating the combination of resistance and endurance training has been conducted mainly on untrained subjects, often runners (such untrained subjects would logically benefit from any form of exercise). Those who deal with higher level athletes would be interested in knowing the effects of resistance training on runners who compete or train for longer distances.

The focus of this specifically defined literature review was to evaluate the effects of CT on performance and/or RE in highly trained endurance runners. The review aimed to answer the following questions: Does RT improve long-distance running performance? If so, what type of RT is best? Which program parameters are most important?

Pertinent Results:

For the purpose of the literature search – the following definitions were employed:
  • Resistance Training: defined as non-running, weight-bearing or weight-loaded activity including free-weight and machine exercises. Subcategories for RT included circuit training (series of free-weight and/or machine exercises performed one after the other with minimal rest between exercises), heavy weight training (dynamic constant RT with exercises such as back squat, and bench press), and explosive strength training (plyometric or stretch-shortening cycle exercises)
  • Highly Trained Runners: defined as those who train ? 30 miles/week or ? 5 days/week
  • Concurrent Training: defined as a RT intervention for a period ? 6 weeks, with running performance distance of 3-42.2 Km
Excluded were studies involving untrained subjects, pre-pubertal children, and elderly populations.

Pertinent Results Include:
  • all five included studies (3-7) demonstrated positive improvements in running performance or RE with CT compared to endurance training alone
  • 4 of the five studies employed plyometric training, while only one (4) utilized heavy resistance training
  • despite a strong relationship between RE and CT, only two of the five studies examined running performance (although VO2, lactate threshold etc. are important to runners, the most important factor for most is race times)
  • one limitation of the studies included was that the training period was relatively short in all of them, averaging about 9 weeks only – therefore, the longer-term effects and adaptations from CT in trained distance runners cannot be determined based on the studies included in this review
  • although each author controlled RT protocols quite carefully, the endurance/running parts of each study were not as tightly controlled and not carefully described

Clinical Application & Conclusions:

This systematic review of five studies on concurrent resistance and endurance training in high level runners suggests that strength training (explosive and/or heavy weight) improves long-distance running performance and/or running efficiency (or RE - an indicator of running performance). At this time, the inclusion of plyometric exercises for highly trained distance runners has the most supporting evidence, while heavier strength training has less, but shows promise. The moderate PEDro scale scores (5 or 6 out of 10) does not diminish the quality and strength of the reviewed studies, considering the constraints that training studies are inherently bound by.

This review was the first attempt to assemble the evidence on this specific and important topic. Although further research is required, the existing literature suggests that resistance training (particularly plyometrics) and distance running cannot only coexist, but enhance running performance and efficiency.

Study Methods:

Five RCTs that met the inclusionary criteria were independently evaluated by two reviewers using the PEDro scale. Scores were recorded, and full consensus was achieved. The authors appropriately pointed out that the CT studies do not score highly on the PEDro scale because of the difficulty of performing blind allocation, treatment, and assessment. PEDro scores the for 5 included studies ranged from 5-6/10 – reasonable scores based on the above-mentioned inherent deficiencies.

Study Strengths / Weaknesses:

This review admittedly included a small volume of literature, yet this was due to the specific topic in question, and therefore does not represent a significant limitation to this study. What it does do however, is emphasize the need for further research in this area.

Additional References:

  1. Abernethy PJ, Jurimae J, Logan PA et al. Acute and chronic response of skeletal muscle to resistance exercise. Sports Med 17: 22–38, 1994.
  2. Kraemer WJ, Deschenes MR, and Fleck SJ. Physiological adaptations to resistance exercise. Implications for athletic conditioning. Sports Med 6: 246–256, 1988.
  3. Mikkola J, Rusko H, Nummela A et al. Concurrent endurance and explosive type strength training improves neuromuscular and anaerobic characteristics in young distance runners. Int J Sports Med 28: 602–611, 2007.
  4. Millet G, Jaouen B, Borrani F, and Candau R. Effects of concurrent endurance and strength training on running economy and VO2 kinetics. Med Sci Sports Exerc 34: 1351–1359, 2002.
  5. Paavolainen L et al. Explosive-strength training improves 5-km running time by improving running economy and muscle power. J Appl Physiol 86: 1527–1533, 1999.
  6. Saunders PU, Telford RD, Pyne DB et al. Short-term plyometric training improves running economy in highly trained middle and long distance runners. J Strength Cond Res 20: 947–954, 2006.
  7. Spurrs RW, Murphy AJ, and Watsford ML. The effect of plyometric training on distance running performance. Eur J Appl Physiol 89: 1–7, 2003.