By Marc Lewis and the Exercise Geeks

Let’s face it: too many coaches and trainers overlook the need for maximal strength and power development in endurance athletes. Sure, it’s easy to simply cast aside the endurance athletes and focus on the high-octane sports like football, basketball, and baseball. After all, specificity dictates that they only need muscular endurance training, right? No doubt, there’s a time and place for high-rep work. But it turns out that well-trained and elite endurance athletes are often just spinning their wheels with too much of it.

Ultimately, the goals of any good strength training program are to optimize performance while reducing injury. Nevertheless, there remain many misconceptions regarding not only the type of strength training that endurance athletes need, but also the adaptations they need to make.

Let’s set the record straight on concurrent training (the practice of training for simultaneous adaptations in both strength/power and endurance) with the help of some science. Although the scientific literature on concurrent training is complex, the quick and dirty summary is as follows:

• Strength/power training enhances endurance performance, primarily through improvements in exercise economy and select anaerobic characteristics (1).
• High intensity (i.e. >80% 1-RM) strength training with explosive intent and/or high velocity movements have been shown to be the most efficient and effective types of resistance training for improving performance in endurance athletes (1).
• Strength/power training does not negatively affect any endurance parameter (including VO2max) (2).
• Endurance training with frequencies exceeding 3 days per week and/or with durations exceeding 40 minutes may blunt muscular adaptations (3).
• Endurance training blunts muscular power to a greater degree than either strength or hypertrophy (3).
• Nutritional considerations, specifically protein intake and nutrient timing, are of a greater importance when training concurrently than when training for strength/power or endurance alone (4).
• For more on concurrent training, check here.

 

General Practical Recommendations

Before we delve deeper into the science, let’s discuss what it all means for typical endurance athletes. Strength training for endurance athletes should focus on enhancing performance through increases in maximal strength, rate of force development, and muscle-tendon stiffness, while also reducing the risk for any adverse effects. In other words, in order to improve performance, the athletes need to get strong.

In terms of strength training, an initial preparatory period of 4-6 weeks is recommended to facilitate the build up to heavier loads. The preparatory period will help the athlete learn the proper movement techniques, as well as increase their work capacity to facilitate their transition into work sets with heavier loads. In addition, as per the literature a period of at least 8 weeks should be allocated before positive adaptations can be expected in all athletes.

The parameters of the strength training sessions should be as follows:

• Frequency: 2-3 sessions per week, dependent on athlete and time of year
• Periodization: Daily undulating (i.e. alternating heavier and lighter days)
• Sets: 2-3, focusing on the muscles used in competition
• Reps: 3-5 on heavier days; 8-10 on lighter days
• Rest: 2-3 minutes, in order to support quality movement, complete recovery, and expression of maximal strength
• Tempo: slow and controlled on eccentric; maximally explosive on concentric

Below are recommendations for how these parameters can be programmed specifically for endurance athletes of all levels. Also included are recommendations for endurance modalities for each athlete.

Practical Recommendations for Endurance Athletes of All Levels

1) Elite Endurance Athlete

“Elite” refers to an endurance athlete that competes at the national and/or international level and in most cases has been training exclusively for high performance for over 10 years.

• Exercise selection: Select exercises that focus on the musculature engaged in their activity (i.e. lower body for cycling/running).
• Intensity: Work at intensities >80% 1-RM for the majority of training while keeping volume to a minimum.
• Tempo: Incorporate explosive, high velocity movements with maximal concentric intent on each rep.
• Periodization scheme: Utilize block periodization. (Note that this recommendation is in contrast with the general recommendation of undulating periodization above. To peak for competition, these athletes require higher volume endurance training, which makes undulating periodization impractical.)
• Frequency: Limit strength training to no more than 2 days/week during competition periods or periods of intense training. Even just one day/week may be sufficient in some cases.
• Endurance modalities: Train for endurance utilizing primarily the modality of his or her sport, but utilize a low-impact modality for active recovery training sessions (i.e. swimming for runners), while keeping heart rate (40-60% HRR) and duration (30-40 minutes) relatively low.

2) Recreational Endurance Athlete

“Recreational” refers to an endurance athlete that competes only in endurance sports but also trains for improvements in body composition and other secondary goals.

• Exercise selection: Select exercises that emphasize total body muscular development.
• Intensity: Work at intensities ranging from 60-90% 1-RM while incorporating loading schemes from the entire repetition continuum (low, moderate, and high).
• Periodization scheme: Apply daily undulating periodization.
• Frequency: Range from 2-4 days/week, depending on factors such as training age, body type, and specific goals.
• Endurance modalities: Train for endurance with a variety of modalities (i.e. cycling, rowing, running, etc.).

3) Hybrid Endurance Athlete

“Hybrid” refers to an endurance athlete that competes in his or her sport occasionally and for fun but has other higher priority goals (body composition, aesthetics, and muscular development).

• Exercise selection: Select exercises that emphasize total body muscular development.
• Intensity: Work at a range of intensities from 60-90% 1-RM while incorporating loading schemes from the entire repetition continuum.
• Periodization scheme: Apply coach’s or athlete’s preferred periodization scheme (any one will do).
• Frequency: Range from 3-5 days/week, depending on factors such as training age, body type, and specific goals.
• Endurance modalities: Use resistance training strategies like metabolic resistance training in conjunction with a variety of aerobic modalities (i.e. running, cycling, swimming, and rucking) to simultaneously improve strength, power, muscular development, and endurance.

What follows is a sample weekly training schedule and the corresponding two-day (post-preparatory) strength training program for a recreational runner in training for a 10K or half marathon.

Table 1. Sample Training Schedule

SUN	MON	TUES	WED	THURS	FRI	SAT
Long Run	Rest Day or Active Recovery*	Easy Pace Training in the AM	Fartlek Run in the AM	Program B in the AM	Rest/Off in the AM	Intervals in the AM
Rest/Off in the PM		Program A in the PM	Active Recovery* in the PM	Active Recovery* in the PM	Tempo/ Pace Run	Rest/Off in the PM

*Active Recovery: This is performed as needed by the athlete (normally once or twice per week) and includes mobility work and/or low intensity (i.e. 40-50% HRR) aerobic training with a low impact modality (i.e. cycling, rowing, etc.).

Table 2. Sample Program A

Exercise	Sets	Reps	Intensity	Rest
Bench Press	3	5	75-80% 1-RM	2-3 min
Back Squat	3	5	75-80% 1-RM	2-3 min
Romanian Deadlift (RDL)	3	5	Movement Skill*	2-3 min
Lateral Lunges (dumbbell)	3	6/side	RPE 8-9†	2-3 min
Pullups	3	6	Use band or machine assistance as necessary	2-3 min

*Begin with medicine ball or kettlebell to learn weight shift, postural alignment, and hip hinge then progress accordingly with loading.

^†RPE defined below.

Table 3. Sample Program B

Exercise	Sets	Reps	Intensity	Rest
Push Press	3	5	75-80% 1-RM*	2-3 min
High Pull	3	5	Movement Skill†	2-3 min
Glute/Ham Raise	3	5	RPE 8-9 w/ banded resistance and isometric hold	2-3 min
Lunges (dumbbell)	3	6/side	RPE 8-9	2-3 min
Bulgarian Split Squat (dumbbell)	3	6/side	RPE 8-9	2-3 min

*This can be an estimated 1-RM from the preparatory period.

^†Teach the movement and add weight accordingly, while requiring the athlete to move the load with maximal velocity and an appropriate intensity of effort.

1-RM vs. Rating of Perceived Exertion (RPE)

In the above example, we’re assuming that we have a 1-RM on the athlete. However, that is not always the case. In many cases, an athlete’s 1-RM early in their strength training program will be inaccurate just a few weeks later. In analogy to many RPE charts that are geared towards aerobic exercise, we’ve developed an RPE chart that bases intensity on how much many reps are “left in the tank” at the end of the set. For example, an RPE of 8-9 indicates that the athlete could have performed 2-4 additional reps before technical failure. When full rest periods are used, this RPE scale correlates remarkably well with percentage-based training. Thus, it can be utilized in lieu of maximal strength testing when the situation warrants.

Table 4. Rate of Perceived Exertion (RPE)

RPE	Level of exertion	Number of Reps Left in the Tank
0-1	None	>10
2-3	Light	8-10
4-5	Medium	6-8
6-7	Moderate	4-6
8-9	Hard	2-4
10	Hardest: at/near failure on last repetition or additional repetitions would compromise form	0-2

Now For the Science

All of the practical recommendations above are important to know. But in order to adapt them to any unique situation, it’s also imperative to know the science of how strength training alters endurance performance. This includes understanding what factors dictate endurance performance, how strength training causes adaptation, and where individual variation fits in.

The Three Determinants of Endurance Performance

There are three main determinants of endurance performance (1):

1. Maximal oxygen consumption (i.e. VO2max)
2. Exercise economy
3. Lactate threshold

Other secondary determinants of endurance performance include running speed and power at VO2max, as well as certain anaerobic characteristics like peak power output. Let’s discuss each of these determinants one by one.

VO2max

VO2max corresponds to the maximal amount of oxygen the body can take up, transport, and utilize during exercise. Currently, there’s little to no evidence demonstrating that any type of resistance training can positively affect VO2max, except in new, untrained endurance athletes when assessing long-term adaptations (1). These athletes could see modest improvements in their VO2max through employing a circuit style resistance training program using higher reps and lighter loads.

Exercise Economy

Exercise economy refers to the oxygen consumption required at a given absolute submaximal exercise intensity (1). Economy actually accounts for the majority of inter-individual variation in endurance sports (5). Numerous research studies demonstrate improvement in exercise economy when utilizing heavy (i.e. >75% 1-RM) and/or explosive, high velocity resistance training (1). Researchers have seen improvements in exercise economy in as little as 2-3 weeks in runners, triathletes, and cross-country skiers. Improvements in exercise economy in cyclists have been shown to take closer to 8 weeks (1).

Lactate Threshold

Lactate threshold denotes the percentage of VO2max at which there is a sharp breakpoint on the lactate curve as a function of exercise intensity (1). Lactate threshold is determined primarily by the two above-mentioned factors (VO2max and exercise economy). Studies evaluating the efficacy of strength training on alterations in the lactate threshold have been inconclusive. However, the investigations have demonstrated an improvement in exercise velocity at the given lactate threshold. As we discussed, VO2max is largely unchanged through strength training, while exercise economy has been shown to improve. Therefore, one may surmise that the lactate threshold is, in fact, positively altered through proper strength training (1).

Secondary Determinants of Endurance Performance

Speed and power output at VO2max have also been shown to predict endurance performance in runners and cyclists (1). These factors incorporate certain anaerobic and neuromuscular characteristics that are elicited through specific maximal strength and explosive type strength training techniques. The ability to generate a high peak power output in a short period of time can have a dramatic effect on a race in terms of making a pass or closing a gap.

Mechanisms of Adaptation

The primary mechanisms by which adaptations in the above factors are thought to occur are altered muscle fiber type recruitment patterns, enhanced maximal force and/or rate of force development, as well as through alterations in the muscle-tendon system (1, 2, 5).

Altered Recruitment Pattern

By increasing the maximal strength of type I muscle fibers – and thereby reducing the relative work of each muscle fiber – time to exhaustion may be extended. This, in turn, will delay the activation of type II muscle fibers. When the activation of type II muscle fibers are delayed, it allows them to be utilized in certain times in the race in order to elicit increases in speed quickly (i.e. closing gap, accelerating up a hill, or sprinting to the finish). Since maximal force is increased, peak tension developed in each movement cycle increases at the same absolute exercise intensity. This enables the athlete to exercise at a lower relative intensity for the same absolute intensity.

Table 5. Muscle Fiber Classification

Type	Twitch Speed	Bioenergetic Pathway
Type I	Slow-twitch	Oxidative
Type IIa	Fast-twitch (a) FTa	Fast oxidative/glycolytic
Type IIx	Fast-twitch (x) FTx	Fast glycolytic

Meanwhile, there’s a shift in muscle fiber type from type IIx to type IIa fibers. Type IIa muscle fibers are more fatigue-resistant than type IIx fibers yet still able to generate high power outputs. In theory, this reduces the reliance on the less efficient type IIx muscle fibers, which would influence exercise economy through a slower emptying of glycogen stores. Therefore, an athlete’s capacity for high-intensity performance could be altered through reducing overall muscular fatigue and increasing time to exhaustion.

Table 6. Characteristics of Fiber Types

Type	Oxidative Capacity	Glycolytic Capacity	Contractile Speed	Fatigue Resistance	Motor Unit Strength
Type I	High	Low	Slow	High	Low
Type IIa	Moderately High	High	Fast	Moderate	High
Type IIx	Low	Highest	Fast	Low	High

Increased Force and Rate of Force Development

Increases in rate of force development and maximal force production facilitate enhanced blood flow to working muscles. This adaptation can result in lower relative exercise intensity and reduced time to reach desired force. This, in turn, can give rise to enhanced exercise economy and alter the absolute workload accomplished at the given relative exercise intensity (i.e. increased velocity at lactate threshold and VO2max).

These alterations are elicited by increased neural activation through high load (>80% 1-RM) movements with explosive intent. A shorter contraction time induced from the increased maximal strength and rate of force development allows the muscle to contract and relax in a shorter period of time, which reduces the amount of time that blood flow is restricted. Physiologically, this enhances oxygen and substrate delivery and therefore delays muscular fatigue (1, 5).

Muscle-tendon Alterations

The stiffness of the muscle-tendon system improves through heavy strength training (i.e. >80% 1-RM) as well as through explosive, high velocity type training (1, 5). When an athlete makes use of the stretch-shortening cycle, as in running, there’s a storage of potential energy that equates to approximately half of the mechanical work performed during the eccentric phase of a running stride. Increased stiffness in the muscle-tendon unit is associated with improved utilization of elastic energy in the unit, which may result in a reduced demand of ATP production at all intensities (1, 5) and, therefore, enhanced running economy.

Individual Considerations

Body Composition

Increases in the cross-sectional area of the muscle are associated with increases in peak power and maximal force, which are favorable adaptations for endurance athletes. However, increased body mass is a potentially negative consequence for endurance athletes – and the precise reason why many strength and conditioning professionals shy away from higher loads.

Nevertheless, the research investigating the effects of supplemental strength training in endurance athletes has neither identified increases in total body mass nor compromised endurance performance parameters (1). In fact, improvements in body composition (i.e. increased fat-free vs. fat mass) would be advantageous to endurance athletes, as long as total body mass stays constant. Increases in fat-free mass while maintaining a constant total body mass could actually support positive effects on performance such as running speed at lactate threshold, as well as peak and mean power output (1).

One oft-cited knock on strength training for endurance athletes is the idea that an increase in muscle cross-sectional area may reduce capillary density, an important endurance adaptation. However, there’s actually no evidence supporting this theory. That is, increases in muscle cross-sectional area in endurance athletes have not been shown to negatively impact oxygen uptake or to reduce capillarization.

Overtraining

Overreaching occurs due to an intensified training period and is considered a normal outcome for athletes due to the ability to recover quickly, and subsequently, enhance performance (6). However, when overreaching is sustained for long periods of time it can transition into overtraining, which can cause performance decrements and require recovery times ranging from several weeks to several months (6).

The potential for chronic overreaching or overtraining must be considered when weighing the merits of adding strength training into a program. Endurance athletes should always be monitored with athlete feedback, paying special attention to phrases like “heavy legs” and athletes complaining of trouble sleeping, eating, or decreased motivation to train (6).

In order to reduce the potential negative side effects associated with chronic overreaching, strength training should be introduced in a low volume manner (i.e. 1-2 sets) in the preparatory period. In addition, strength training should actually replace some of the endurance training, as opposed to simply being added with no reduction in endurance training volume. It has been suggested that two days of strength training should replace approximately 10% of the endurance training volume (1). For example, if a cross-country runner is averaging 75 miles per week of endurance volume, a reduction of approximately 7-8 miles per week would be adequate when supplemental strength training is added.

Final Thoughts on Strength Training for Endurance Athletes

There you have it: the science and practice of strength training for endurance athletes. Clearly, the science shows that implementing strength training into an endurance athlete’s overall training has numerous performance-enhancing effects – provided it’s done correctly, of course. Remember, as with any type of programming, it’s critical to evaluate the individual athlete’s training age and goals. Also be mindful that the addition of strength training will likely mean a corresponding reduction in endurance training volume. Some would call this blasphemy; we call it evidence-based training.

References

1. Ronnestad, B.R. & Mujika, I. (2013). Optimizing Strength Training for Running and Cycling Endurance Performance: A review. Scandinavian Journal of Medicine & Science in Sports. 24: 603-612.
2. Leveritt, M., Abernethy, P.J., Barry, B.K., & Logan, P.A. (1999). Concurrent Strength and Endurance Training. Sports Medicine. 28(6): 413-427.
3. Wilson, J.M., Marin, P.J., Rhea, M.R., Wilson, S.M., Loenneke, J.P., & Anderson, J.C. (2012). Concurrent Training: A meta-analysis examining interference of aerobic and resistance exercise
4. Baar, K. (2014). Using Molecular Biology to Maximize Concurrent Training. Sports Medicine. 44(suppl 2): S117-S125.
5. Hoff, J. (2006). Muscular Strength Training Effects on Aerobic Endurance Performance. 5th International Conference on Strength Training.
6. Halson, S.L. & Jeukendrup, A.E. (2004). Does Overtraining Exist? Sports Medicine. 34(14): 967-981.