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Original Research

Effect of Concurrent Resistance and Endurance Training on Physiologic and Performance Parameters of Well-Trained Endurance Cyclists

Levin, Gregory T1; Mcguigan, Michael R2; Laursen, Paul B2

Author Information
Journal of Strength and Conditioning Research: November 2009 - Volume 23 - Issue 8 - p 2280-2286
doi: 10.1519/JSC.0b013e3181b990c2
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Abstract

Introduction

Successful endurance cycling performance relies on a number of physiologic, biomechanical, and psychological factors (5). The most influential factor in this success-determining matrix appears to relate directly to the type and amount of training performed by the cyclist (24). This has prompted researchers to continue exploration into the most effective means of training for endurance cyclists. Optimal training programs for cyclists are vague, and it remains unclear as to whether the augmentation of an endurance training program with resistance training exercises can acutely enhance certain aspects of cycling performance (23).

Concurrent strength and endurance training has received much attention as an alternative form of training for endurance athletes (8,14,17,26). This form of training has proven to be successful at improving endurance performance in well-trained runners (20,28) and cross-country skiers (18). Only a limited number of studies, however, have examined its effect in cyclists (7,9,19,30), and these studies have revealed equivocal findings. The earliest of these studies by Bishop et al. (9) examined the effect of a 12-week concurrent endurance/heavy resistance training program in female cyclists and found an increase in leg strength without a change in endurance performance, lactate threshold, or peak oxygen uptake (9). A second study by Bastiaans et al. (7) also found that 1-hour time trial performance was unaffected when a portion of endurance training was replaced by explosive-type resistance training. Despite the reduction in endurance training volume in this study, short-term performance (average power output measured over 30 s) was maintained in the RT group but was found to decrease in the group that only completed cycle training (7). This finding could suggest that resistance training might serve to enhance high-intensity (all out) cycling performance, an aspect of certain importance for successful cycling (4).

Improvements in endurance cycling performance after concurrent resistance and endurance training were recently shown by Paton and Hopkins (30). The authors examined the effect of concurrent unilateral resistance exercises combined with high-intensity interval training on cycling performance and found that power output over 1- and 4-km time trial distances was improved over a control group maintaining their usual endurance cycle training. Although the findings of Paton and Hopkins (30) provide support for the use of concurrent strength and endurance training, the fact that resistance-type training was performed in conjunction with high-intensity interval training makes it difficult to decipher the degree to which the resistance training in isolation made toward the enhancement of the cycling performance shown. Indeed, the effects of high-intensity interval training in cyclists are well known (25). As well, a recent study by Jackson et al. (19) reported that neither high-resistance/low-repetition nor high-repetition/low-resistance training was beneficial for improving maximal oxygen uptake, maximum power output during a graded exercise test (GXT) or cycling economy for both male and female trained cyclists. These combined findings suggest that resistance training does not compromise endurance cycling performance and that explosive resistance training may enhance high-intensity, short-term cycling power output. Nevertheless, the effect of concurrent resistance and endurance training on dynamic cycling performance (i.e., high-intensity surges within an endurance cycling trial) is not known. Moreover, in all previous studies with trained cyclists, the focus of the resistance training has been on heavy resistance training (9), explosive training (7), or muscular endurance in isolation (19). Some research suggests, however, that combined weight training incorporating both high-force and high-power training is most beneficial for improvements in muscular speed, power, and strength (15), factors that may be of importance for various aspects of cycling performance.

In light of the uncertain effects of resistance training on dynamic cycling performance, the purpose of this study was to examine the effect of supplementing an endurance trained cyclist's regular training workload with a 6-week undulating, periodized resistance training program and to observe the effects on high-intensity sprinting and endurance cycling performance.

Methods

Experimental Approach to the Problem

This study examined the influence of adding a multidimensional resistance training program on high-intensity sprinting and endurance performance in trained cyclists. All previous studies in this area have used only 1 form of resistance training (heavy training, explosive training, or training for muscular endurance) throughout the intervention program. The present study attempted to answer the question of whether incorporating resistance training into the training regime of already trained cyclists is beneficial to dynamic endurance cycling performance, which is most often characterized by moderate intensity work periods interspersed with high-intensity maximal work efforts (4). Measurements of endurance, power, strength, and performance were assessed before and after a 6-week intervention period in a group that performed resistance training on top of their normal cycle training program and a group that only performed their normal endurance training regimen.

Subjects

Seventeen well-trained male cyclists/triathletes involved in competition for a minimum of 12 months participated in the study. The training intervention took place during the noncompetitive phase of the year when no racing was occurring. Because of injuries and illnesses unrelated to the resistance protocol, 3 participants withdrew before completion of the study. The remaining 14 subjects (mean [SD] age 31 [8] yr; stature 179.9 [8.6] cm; body mass 77.4 [8.6] kg) were randomly divided into a resistance training group (RT, n = 7) and a control group (CON, n = 7). Participation was limited to individuals who had not performed lower-body resistance training for at least 6 months before study start. All subjects, whose characteristics are shown in Table 1, were informed of risks to participation before providing written informed consent before study commencement. The study was approved by the Institutional Human Research Ethics Committee.

Table 1
Table 1:
Subject characteristics of the resistance training (RT) and control (CON) groups presented as mean (SD)

Procedures

In the week before and after the intervention period, physical and physiologic measurements were recorded over 2 consecutive days. On day 1, participants completed a 1 repetition maximum (1RM) squat test for assessment of maximal strength as well as a GXT. On the following day, subjects completed a 30-km dynamic cycling test (CT30) on a stationary cycle ergometer (2,3). All participants were accustomed to performing the various testing procedures. Participants were required to maintain a training diary for 2 weeks before start of the training period, as well as throughout this period, in which they recorded the cycling duration, cycling distance, and cycling intensity of each cycling session during the training period (Table 2).

Table 2
Table 2:
Average weekly time and distance of regular cycling training recorded in training diaries for the resistance training (RT) and control (CON) groups recorded for an average week before (Pre) and during the study (During).

Maximal Graded Exercise Test

The GXT was performed on a calibrated Velotron cycle ergometer (Racermate, Seattle, WA, USA) with the accompanying Velotron Coaching Software to determine peak power output (PPO) (3). A TrueOne Gas Analyzer (Parvomedics, Sandy, UT, USA) was used to determine maximal oxygen uptake (O2max). The GXT began at 100 W and increased by 50 W every 5 minutes. Each test concluded when the participant reached volitional exhaustion. Maximal oxygen uptake was defined as the highest (O2max)value recorded and averaged over a 30-second period. The PPO was recorded as the power output of the last completed stage plus the fraction of the workload during which fatigue was reached (16).

Cycling Performance Test

A CT30 was used to assess both sprint and endurance performance. The time trial, a modified version of the 100-km time trial designed by Schabort and colleagues (32), included sprint sections that were interspersed within the 30-km test. This test has recently been shown to be reliable (coefficient of variation = 2.4%, intraclass correlation coefficient = 0.93) after habituation (2). In this test, 3 250-m sprints were performed at 4, 14, and 24 km, and 31-km sprints were performed at 9, 19, and 29 km, a format that permitted analysis of high-intensity sprint performance within an endurance time trial. A standardized 10 minute warm-up was performed before the time trial. The warm-up consisted of cycling at 25% PPO for 3 minutes, 60% for 5 minutes, and 80% for 2 minutes. During the time trial, heart rate, average and instantaneous (accurate to 1 s) speed, power and cadence, as well as distance and elapsed time were continuously recorded.

Subjects were blinded from all other forms of external feedback apart from the distance completed during the time trials. Knowledge of the time trial distance allowed subjects to be aware of when they were approaching each sprint. However, verbal reminders were also given to alert the rider of each upcoming sprint. Participants were encouraged to perform maximally throughout the entire sprint. Power output was verified using a scientific version SRM (Schoberer Rad Mebtechnik, Welldorf, Germany), and PPO was determined as the highest power averaged and recorded each second (3).

The Velotron cycle ergometer was adjusted to replicate the settings on each individual's own road bicycle. Settings on the subject's actual bicycle were recorded during the first visit to the laboratory and replicated for all subsequent visits. Stable environmental conditions during the tests were maintained in a climate chamber set at 16°C with a relative humidity of 40%. Furthermore, a large fan was positioned to face each cyclist front-on and provided head-winds similar to those experienced during outdoor cycling (approximately 32 km/hr) (31). Water was permitted as desired during the time trials.

Strength Testing

The 1RM squat was used to assess lower-limb muscular strength. The testing procedure included a warm-up set of 6 lifts, a heavier set of 3 lifts, followed by 1 repetition sets (13). The first 1RM attempt was performed at an estimated resistance that would allow the completion of only 1 lift. After each successful lift, additional resistance was added until the subject's 1RM was determined. The 1RM was always completed within 5 attempts in accordance with previous recommendations (27).

Training Program

Resistance training was performed 3 times per week, for 6 weeks, using a nonlinear periodization model. Of the 3 sessions per week, 1 session focused on the development of muscle strength, 1 on the development of power, and 1 on muscle hypertrophy (Table 3) (21). A minimum of 24 hours separated each resistance training session. Notably, the resistance exercises attempted to emphasize single-leg movements to provide added neuromuscular specificity to the training program for the cyclists because the driving phase of cycling is predominantly a unilateral exercise (30). Additional resistance was added at the discretion of the investigators to maintain specific percent 1RM intensities throughout the training period to comply with the specific outcome of each session. Power exercises were performed for 3 sets (6 reps), hypertrophy exercises were performed for 3 sets (12 reps), and strength exercises were performed for 4 sets (5 reps). Recovery between sets and exercises was set at 2 minutes for all resistance training. Each session began with a 5 minute warm-up performed on a cycle ergometer (Monark, 818E, Stockholm, Sweden) at a self-selected pace. The RT group began their training program under instruction not to compromise their normal endurance training regimen. Participants were expected to attend all training sessions, but compliance was set at 94% (17 of 18 sessions) for subjects to remain in the study.

Table 3
Table 3:
Exercise order for power, hypertrophy, and strength training sessions.*

Statistical Analyses

A one-way analysis of variance (ANOVA) was used to determine differences between groups. A two-way (group × time) ANOVA delineated differences between the dependant variables of strength and endurance performance between groups before and after the training intervention. To assess the change in strength and power between the groups after the intervention, a paired t-test was used. Cohen's effect sizes (ES) were used to determine clinical significance between the mean of the variables over time. Significance, in all cases, was set at an alpha level of 0.05, and data are presented as means and SDs.

Results

The subject characteristics of both groups are shown in Table 1. Although there were no differences in stature, mass, or 1RM, the CON group was found to be older than the RT group (p < 0.05). Table 2 shows the time spent training and the training distance. Neither group was shown to alter their cycle training during the study. However, the RT group decreased their cycle training duration slightly (3%), whereas the amount of riding time increased slightly for the CON group (8%). This resulted in an ES of 0.5 between the groups.

The change in lower-limb strength was assessed with the 1RM squat. Strength after the 6-week training period increased from 109 (18) kg to 137 (21) kg and 106 (20) kg to 113 (22) kg in the RT and CON groups, respectively (p = 0.2). No difference in 1RM was found between groups (p = 0.2). However, the change in 1RM was greater for the RT compared with the CON group (p = 0.002; ES = 1.1) (Figure 1).

Figure 1
Figure 1:
Percentage change in the 1RM squat for the resistance training (RT) and control group (CON) from pre- to postmeasurement. *Significant difference between groupsp < 0.05.

No differences were found between the average power produced during the CT30 for either the RT group or the CON group, both before and after the training period. Before training, time to complete the CT30 and average power output was 2,823 (142) seconds and 295 (43) W for the RT group and 2,851 (125) seconds and 285 (33) W for CON. After the training period, time to complete the CT30 and average power output was 2,825 (104) seconds and 295 (31) W for the RT and 287 (31) W and 2,841 (119) seconds for the CON group, respectively. The change in average power output and PPOs for the 250-m sprints and 1-km sprints are shown in Figure 2. No differences were found between the change in absolute power output between groups. However, the change in peak power over the last 1-km sprint was found to be greater in the CON group compared with the RT group.

Figure 2
Figure 2:
Percent changes in the average power output during the 250-m and 1-km sprints (A, B) and peak power output during the 250-m and 1-km sprints (C, D) for the resistance training (RT) and control (CON) groups measured before and after the intervention using an SRM power meter. *Significant difference between groupsp < 0.05.

There was no change in average power output in either group during sprint or steady state periods after the training period. Power output increased by 4% during both the first 250-m and first 1-km sprint in the RT group, as shown by the small ES (0.3) found for both comparisons. The RT group also increased PPO during the 14-km sprint by 6% (ES = 0.4) but decreased peak power by 5% in the final sprint (ES = −0.4). The CON group increased PPO in the final 3 sprints, by 13%, 7%, and 11% respectively, resulting in ESs of 0.8, 0.3, and 0.5, respectively.

Because the CON group increased PPO in the final 3 sprints, analysis of the change in PPO over time between the 2 groups resulted in ESs of −0.9, −0.6, and −0.9 for the final 3 sprints, respectively. Furthermore, the increased change in mean power output in the CON group and decreased change in mean power output during the last sprint in the RT group resulted in an ES of −0.5 between groups.

Graded exercise test results are shown in Table 4. Both the RT and CON groups showed similar values of (O2max) and PPO both before and after the training period. No differences in these variables were found between groups.

Table 4
Table 4:
Maximal oxygen uptake (JOURNAL/jscr/04.02/00124278-200911000-00014/ENTITY_OV0312/v/2017-07-20T235409Z/r/image-pngO2max) and peak power output (PPO) recorded during graded exercise test before (pre) and after (post) training period.

Discussion

The purpose of this study was to supplement an endurance cyclists' regular training regime with a 6-week lower-leg resistance training program and to examine its effect on dynamic cycling performance, lower-leg strength, and physiologic parameters. The main finding was that despite an improvement in lower-leg strength (Figure 1), the concurrent endurance and resistance training program did not enhance markers of endurance capacity, endurance cycling, or dynamic sprint performance compared with a CON group that performed their normal endurance training program (Figure 1).

The finding of no change in markers of endurance capacity or endurance performance after a period of concurrent training is consistent with most studies (9,30). For example, Bishop et al. (9) found no change in (O2max) or average power produced over 1-hour time trial after a period of concurrent resistance and endurance training in female cyclists. Nevertheless, Paton and Hopkins (30) found that 1- and 4-km time trial performance increased after adding explosive-type resistance training and high-intensity interval training to a cyclist's regular endurance training program. However, the improvement in 1- and 4-km sprint performance shown in this study (30) could have been caused by the high-intensity interval training because similar improvements in performance have been shown with such training in isolation (25). Thus, it is unclear whether concurrent resistance and endurance training can enhance high-intensity cycling performance (23).

Because the present study was interested in determining whether resistance training would benefit the high-intensity periods intrinsic to field cycling performance (4), we designed a dynamic cycling test with intermittent short (250-m) and long (1-km) sprint periods (2). We hypothesized that resistance training would result in improvements to peak and mean power output during these sprints. This, however, did not occur (Figure 2). Despite the 26% increase in squat strength in the RT group (Figure 1), there was more of a trend to suggest that sprinting performance declined, particularly with increasing time trial distance. Nevertheless, the 4% improvement in initial 250-m sprint performance shown by the RT group could suggest that strength training may benefit sprint cycling performance. This finding supports the popular sentiment that resistance training may benefit short-duration, high-intensity cycling performance, such as that performed during a short-duration track cycling event (e.g. Kilo and Sprint), but is likely to be of less importance for endurance cycling (road) performance.

The training period of 6 weeks (18 sessions) was similar to other programs applied in the concurrent training literature (9,29,30,34). Furthermore, muscle mass and muscle architecture have been shown to increase in as little as 5 weeks with concurrent training (10), and performance has been shown to improve after as few as 12 to 18 resistance training sessions added to the regular endurance training program in runners (34) and cyclists (30). Resistance training is known to increase the cross-sectional area of the muscle, cause neuromuscular adaptations, and increases the contractile muscle proteins (11,12), all adaptations that could assist in the development of cycling power output. Indeed, previous studies have shown that Wingate power output (6,22,26) and short-term cycling performance (17) can increase after resistance training programs ranging from 6 weeks to 9 months. However, these previous studies used a separate test to determine maximal power output on the bike, with subjects exerting maximal effort from a rested state, whereas short-term performance in the current study was assessed during sprint periods integrated into the CT30 trial. Thus, resistance training can likely enhance short-term anaerobic performance from a rested state but is unlikely to improve dynamic high-intensity sprint performance within an endurance cycling event.

There are a few possible reasons why the resistance training program in the present study did not enhance markers of dynamic cycling time trial performance. Although Bastiaans et al. (7) found that the average power output of an all-out 30-second test (short-term power) decreased after 9 weeks for a control group but remained stable when resistance training was added to endurance training, these authors reduced the amount of endurance training in accordance with the amount of resistance training performed. In the current study, resistance training was added to the endurance training program. It is possible that the increased work completed by participants in the RT group may have caused overreaching and the lack of performance enhancement shown.

A second possible reason for the lack of improvement in sprinting performance shown after the concurrent resistance training program is that the current study investigated the average power output and PPO of each sprint using a closed loop test. Because subjects were instructed to complete the overall 30-km time trial in the shortest possible time, as well as give maximal efforts during the sprinting sections, it is possible that pacing strategies may have impacted the sprinting results (2), with cyclists consciously or unconsciously aware that variable pacing can impair overall performance (1). However, because the main objective of this study was to investigate how concurrent resistance and endurance training impacted on overall endurance cycling performance, sprinting during the actual performance test was seen as being more important to include than sprinting during an isolated test.

A third reason for the lack of improvement in the sprint performance shown after resistance training may be caused by the concept of lag time. Lag time has been explained by Stone and colleagues (33) as the time needed by an athlete to use the gains made from training. It is possible that the 6 weeks of resistance training followed immediately by post-testing (up to 14 days after the last training session) did not allow sufficient recovery time for cyclists to develop the muscular power that could be translated into enhanced cycling performance. Performance modeling research is required to uncover how varying fitness and fatigue parameters influence the cycling performance continuum (i.e., sprint and endurance cycling performance).

A final reason for the lack of improvement in sprint performance shown after concurrent training may relate to the lack of specificity of resistance training. Indeed, muscular force, repetition number, and specific movement patterns of resistance training might not replicate the demands of endurance cycling performance. For example, the 5 to 12 repetitions completed during a single resistance training set are markedly lower than the estimated 28, 113, and 3,840 repetitions performed during 250-m sprints, 1-km sprints, and 30-km time trial, respectively (assuming an 80 rpm cadence). In an Internet resource, Coggan highlights how increasing lower-limb strength does not necessarily improve pedal force applied at the high pedal velocities that occur during cycling performance, even during sprinting (http://home.earthlink.net/∼acoggan/misc/id4.html). Indeed, the improvements in 1RM shown after resistance training in the present study were likely achieved through improvements in force output applied at low angular velocities, whereas the forces applied during the sprints in the dynamic cycle test would have been performed at high angular velocities. Moreover, despite the unilateral nature of the strength training exercises performed by the RT group in the present study (Table 3), such exercises are not precisely specific to the recruitment patterns applied during cycling. A more common form of strength training performed by cyclists is named strength endurance training (i.e., http://home.earthlink.net/∼acoggan/setraining). During strength endurance training, cyclists pedal for prolonged periods (e.g., from 5-20 min) at moderate to high intensities at abnormally low pedal rates (e.g., 45-75 rpm). Future studies are needed examine whether specific strength endurance training (i.e., high-intensity, low-cadence training) can improve dynamic cycling performance.

In conclusion, despite a 26% increase in squat strength, the addition of a 6-week lower-leg undulating resistance training program to the normal endurance cycle training program of trained cyclists did not improve sprint or overall performance during a CT30 trial. Although concurrent strength and endurance training does not appear to benefit dynamic cycling performance, future studies are needed to examine the influence of specific strength endurance training on endurance cycling performance.

Practical Applications

Concurrent strength and endurance training in well-trained cyclists appears to offer no benefit to dynamic cycling time trial performance over 30 km. Previous studies have shown that short-duration sprinting in isolation can be enhanced after concurrent training, and findings from the present study suggest that initial cycle sprint ability may also be enhanced. However, as event duration extends, it is less likely that resistance training will assist with any aspect of endurance cycling performance. Indeed, after the 20-km mark of the time trial in the current study, the concurrent training group tended to reduce their sprint performance. Thus, although resistance training may be a good form of alternate training to apply during the off-season of a cyclist's yearly training program and is likely to be of benefit for track cycling performance (i.e., Kilo and Sprint), it is unlikely to enhance dynamic endurance cycling performance, such as road race performance. Because cyclists commonly perform “strength endurance” sessions, future research is needed to investigate its effect on dynamic endurance cycling performance.

References

1. Abbiss, C and Laursen, PB. Describing and understanding pacing strategies during athletic competition. Sports Med 38: 239-252, 2008.
2. Abbiss, C, Levin, G, McGuigan, MR, and Laursen, P. Reliability of power output during dynamic cycling. Int J Sports Med 29: 574-578, 2008.
3. Abbiss, CR, Quod, MJ, Levin, G, Martin, DT, and Laursen, PB. Accuracy of the Velotron ergometer and SRM power meter. Int J Sports Med 30: 107-112, 2009.
4. Abbiss, CR, Straker, L, Quod, M, Martin, D, and Laursen, PB. Examining pacing profiles in elite female road cyclists using exposure variation analysis. Br J Sports Med. [Epub ahead of print].
5. Atkinson, G, Davison, R, Jeukendrup, A, and Passfield, L. Science and cycling: Current knowledge and future directions for research. J Sports Sci 21: 767-787, 2003.
6. Balabinis, CP, Psarakis, CH, Moukas, M, Vassiliou, MP, and Behrakis, PK. Early phase changes by concurrent endurance and strength training. J Strength Cond Res 17: 393-401, 2003.
7. Bastiaans, JJ, van Diemen, ABJP, Veneberg, T, and Jeukendrup, AE. The effects of replacing a portion of endurance training by explosive strength training on performance in trained cyclists. Eur J Appl Physiol 86: 79-84, 2001.
8. Bell, GJ, Syrotuik, DG, Attwood, K, and Quinney, HA. Maintenance of strength gains while performing endurance training in oarswomen. J Appl Physiol 18: 104-115, 1993.
9. Bishop, D, Jenkins, DG, Mackinnon, LT, McEniery, M, and Carey, MF. The effects of strength training on endurance performance and muscle characteristics. Med Sci Sports Exerc 31: 886-891, 1999.
10. Blazevich, AJ, Gill, ND, Bronks, R, and Newton, RU. Training-specific muscle architecture adaptation after 5-wk training in athletes. Med Sci Sports Exerc 35: 2013-2022, 2003.
11. Coffey, VG, Shield, A, Canny, BJ, Carey, KA, Cameron-Smith, D, and Hawley, JA. Interaction of contractile activity and training history on mRNA abundance in skeletal muscle from trained athletes. Am J Physiol Endocrinol Metab 290: E849-E855, 2006.
12. Docherty, D and Sporer, B. A proposed model for examining the interference phenomenon between concurrent aerobic and strength training. Sports Med 30: 385-394, 2000.
13. Faigenbaum, AD, Milliken, LA, and Westcott, WL. Maximal strength testing in healthy children. J Strength Cond Res 17: 162-166, 2003.
14. Häkkinen, K, Alen, M, Kraemer, WJ, Gorostiaga, E, Izquierdo, M, Rusko, H, Mikkola, J, Häkkinen, A, Valkeinen, H, Kaarakainen, E, Romu, S, Erola, V, Ahtiainen, J, and Paavolainen, L. Neuromuscular adaptations during concurrent strength and endurance training versus strength training. Eur J Appl Physiol 89: 42-52, 2003.
15. Harris, GR, Stone, MH, O'Bryant, HS, Proulx, CM, and Johnson, RL. Short-term performance effects of high power, high force, or combined weight-training methods. J Strength Cond Res 14: 14-20, 2000.
16. Hawley, JA and Noakes, TD. Peak power output predicts maximal oxygen uptake and performance time in trained cyclists. Eur J Appl Physiol Occup Physiol 65: 79-83, 1992.
17. Hickson, RC, Dvorak, BA, Gorostiaga, EM, Kurowski, TT, and Foster, C. Potential for strength and endurance training to amplify endurance performance. J Appl Physiol 65: 2285-2290, 1988.
18. Hoff, J, Helgerud, J, and Wisløff, U. Maximal strength training improves work economy in trained female cross-country skiers. Med Sci Sports Exerc 31: 870-877, 1999.
19. Jackson, NP, Hickey, MS, and Reiser, RF. High resistance / low repetition vs. low resistance / high repetition training: effects on performance of trained cyclists. J Strength Cond Res 21: 289-295, 2007.
20. Johnston, RE, Quinn, TJ, Kertzer, R, and Vroman, NB. Strength training in female distance runners: Impact on running economy. J Strength Cond Res 11: 224-229, 1997.
21. Kraemer, WJ and Ratamess, NA. Fundamentals of resistance training: Progression and exercise prescription. Med Sci Sports Exerc 36: 674-688, 2004.
22. Kraemer, WJ, Ratamess, NA, Fry, AC, Triplett-McBride, T, Koziris, LP, Bauer, JA, Lynch, JM, and Fleck, SJ. Influence of resistance training volume and periodization on physiological and performance adaptations in collegiate women tennis players. Am J Sports Med 28: 626-633, 2000.
23. Laursen, PB, Chiswell, SE, and Callaghan, JA. Should endurance athletes supplement their training program with resistance training to improve performance. Strength Cond J 27: 2-7, 2005.
24. Laursen, PB and Jenkins, DG. The scientific basis for high-intensity interval training: Optimising training programmes and maximising performance in highly trained endurance athletes. Sports Med 32: 53-73, 2002.
25. Laursen, PB, Shing, CM, Peake, JM, Coombes, JS, and Jenkins, DG. Influence of high-intensity interval training on adaptations in well-trained cyclists. J Strength Cond Res 19: 527-533, 2005.
26. Leveritt, M, Abernethy, PJ, Barry, B, and Logan, PA. Concurrent strength and endurance training: The influence of dependent variable selection. J Strength Cond Res 17: 503-508, 2003.
27. McBride, J, Triplett-McBride, T, Davie, A, Abernethy, P, and Newton, R. Characteristics of titin in strength and power athletes. Eur J Appl Physiol 88: 553-557, 2003.
28. Paavolainen, L, Häkkinen, K, Hämäläinen, I, Nummela, A, and Rusko, H. Explosive-strength training improves 5-km running time by improving running economy and muscle power. J Appl Physiol 86: 1527-1533, 1999.
29. Paavolainen, L, Hakkinen, K, and Rusko, H. Effects of explosive type strength training on physical performance characteristics in cross-country skiers. European J Appl Physiol Occup Physiol 62: 251-255, 1991.
30. Paton, CD and Hopkins, WG. Combining explosive and high-resistance training improves performance in competitive cyclists. J Strength Cond Res 19: 826-830, 2005.
31. Saunders, AG, Dugas, JP, Tucker, R, Lambert, MI, and Noakes, TD. The effects of different air velocities on heat storage and body temperature in humans cycling in a hot, humid environment. Acta Physiol Scand 183: 241-255, 2005.
32. Schabort, EJ, Hawley, JA, Hopkins, WG, Mujika, I, and Noakes, TD. A new reliable laboratory test of endurance performance for road cyclists. Med Sci Sports Exerc 30:1744-1750, 1998.
33. Stone, MH, O'Bryant, HS, McCoy, L, Coglianese, R, Lehmkuhl, M, and Schilling, B. Power and maximum strength relationships during performance of dynamic and static weighted jumps. J Strength Cond Res 17: 140-147, 2003.
34. Turner, AM, Owings, M, and Schwane, JA. Improvement in running economy after 6 weeks of plyometric training. J Strength Cond Res 17: 60-67, 2003.
Keywords:

power output; sprinting; strength; athlete

© 2009 National Strength and Conditioning Association