1. Effects of Plyometric Training on Lower-Body Muscle Function in Novice Marathon Runners Jesse A. Stein 1, Chris J. Lundstrom 2, Morgan R. Betker 2, & John S. Fitzgerald 1 University of North Dakota 1, Grand Forks, ND, USA University of Minnesota 2, Minneapolis, MN, USA Sponsor: Dr. Jim Whitehead, FACSM ABSTRACT Background: Improvements in lower-body force production during concurrent endurance and explosive training have been reported in competitive runners, yet few studies investigate the effects of such training on muscle function in novice runners training for distances beyond 10,000 meters. Method: Students were recruited from a marathon training course. Participants were block randomized into two groups: plyometric/explosive speed training (PLYO) or core stability training (CORE). Squat jump (SJ) and counter-movement jump (CMJ) were evaluated using a force platform. Data were sampled at 1202Hz and filtered using a fourth-order Butterworth low-pass filter (50Hz). Dependent measures were peak force, average rate of force development (RFD), peak RFD and jump height, which were determined from the average of three jumps at the beginning and end of the 12-week intervention. A one-way analysis of covariance was conducted to discern between-group differences in jumping performance after the intervention. Results: Vertical jump data were available for 20 participants (Mean ± SD: age = 20.4 ± 1.3 yr, height = 172.1 ± 9 cm, weight = 70.3 ± 10 kg, BMI = 23.5 ± 1.9 kg·m -2, 11 female). After adjusting for pre-intervention values, there was no significant difference between PLYO and CORE on post-intervention jump height during either SJ (p = 0.07, partial eta squared = 0.18) or CMJ (p =.57, partial eta squared 0.02). Post-intervention values for peak force, average RFD and peak RFD did not differ between groups for either jump. Conclusion: Jumping performance parameters were not affected by the 12-week PLYO intervention while concurrently training for a marathon. It appears that the high running volume associated with marathon training negatively influences the ability to increase lower-body force and power production in novice marathon runners. It is possible that one exposure per week of plyometric training performed after a 40-minute training run was insufficient to elicit adaptation in jumping performance. Future investigations should increase the frequency of plyometric training exposure and conduct this training before the days training run. Twenty participants (11 female, 9 male; 10 CORE, 10 PLYO) jumping performance was assessed using a force platform during CMJ and SJ pre- and post-intervention. The marathon training course was a 5 month progressive build-up of mileage with participants running 4-5 days per week. PLYO and CORE sessions were additional to the course, and consisted of one 15-20 minute workout per week for 12 weeks. Sessions took place after a class session 40 minute run. Pre-testing and post-testing occurred prior to and at the end of the training intervention. A one-way analysis of covariance was conducted to detect between- group differences in jumping performance after the intervention. CONCLUSION Jumping performance parameters were not significantly different between PLYO and CORE. It is possible that the training stress from high-volume running caused adaptations from PLYO to be diminished, thus reducing the likelihood of improving jump performance. Future investigations should increase the frequency of PLYO and conduct PLYO on days without endurance training to determine if explosive-strength training regimens are compatible with endurance training in novice running participants. PURPOSE To investigate the effects of PLYO on muscle function in novice runners training for a marathon. REFERENCES 1. Cormie, P., McBride, J. M., & McCaulley, G. O. (2008). Power-time, force-time, and velocity-time curve analysis during the jump squat: Impact of load. Journal of Applied Biomechanics, 24(2), 112–120. 2. Mikkola, J., Rusko, H., Nummela, a, Pollari, T., & Häkkinen, K. (2007). Concurrent endurance and explosive type strength training improves neuromuscular and anaerobic characteristics in young distance runners. International Journal of Sports Medicine, 28(7), 602–11. http://doi.org/10.1055/s-2007-964849 3. Rønnestad, B. R., & Mujika, I. (2014). Optimizing strength training for running and cycling endurance performance: A review. Scandinavian Journal of Medicine and Science in Sports, 24(4), 603–612. http://doi.org/10.1111/sms.12104 4. Taiple, R., Mikkola, J., Salo, T., Hokka, L., Viesterinen, V., Kraemer, W., … Hakkinen, K. (2014). Mixed Maximal and Explosive Strength Training in Recreational Endurance Runners. Journal of Strength and Conditioning Research, 28(3), 689–699. 5. Wilson, J., Marin, P., Rhea, M., Wilson, S., Loenneke, J., & Anderson, J. (2012). Concurrent Training: a Meta-Analysis Examining Interference of Aerobic and Resistance Exercises. Journal of Strength and Conditioning Research, 26(8), 2293–2307. METHOD DESCRIPTIVE ANALYSIS BACKGROUND Endurance performance can be enhanced through concurrent training methods; the combination of strength exercises in an endurance training regimen (3). One form of concurrent training utilizes explosive-strength or plyometric training (PLYO). Researchers have demonstrated that PLYO can enhance anaerobic and neuromuscular characteristics (2). One characteristic concurrent training appears to enhance is jumping ability measured using a force platform (4), although some researchers suggest that strength adaptations might be compromised during high-volumes of endurance training (5). PLYO has similar effects on improved jumping ability in untrained populations (1), yet few studies have examined these effects within concurrent training models. Further, no studies have investigated the effects of PLYO on jumping ability in novice marathoners during the specific-preparation period of their endurance training. Figure 3: CORE training protocol Figure 4: PLYO training protocol Figure 2: Endurance training volume. Table 1: Group descriptive analysis. COREPLYO Age (years)19.8 ± 1.320.8 ± 1.3 Sex (M/F)4,65,5 Weight (kg)72.0 ± 8.868.5 ± 11.3 Height (cm)172.5 ± 7.9172.0 ± 10.4 Sessions Completed10.8 ± 1.510.6 ± 2.0 Sess #Crunch Side crunch Sit- upsV-sit Supe rman Bac kupPlank Side Plank Fire Hydrant Sw. Ball Add.Bridge Bird Dog 11x20 30s1x20 2 1x1 0 30s1x20 3 1x30 45s 1x30 4 1x15 45s 1x30 5 2x20 60s 2x20 6 2x10 60s 2x20 7 2x30 2x45s 2x30 8 2x15 2x45s 2x30 9 3x30 2x60s 3x30 10 3x30 3x15 2x60s 3x30 11 2x30 60s 2x30 12 2x30 2x15 60s 2x30 TRAINING INTERVENTION Sess # 50-m Build 30-m Fly 60-m spr. In-n- Out Frog Hops Alt. Leg Bound S.Leg Fwd Hop Lat. Cone Jumps F/B Cone Jumps Squat Jump Split Scissor Jump Depth /box Jump 1 22 1x102x101x8 1x10 2 22 1x8 3 33 2x82x151x12 2x8 4 33 1x15 2x81x12 5 33 2x102x202x10 6 33 1x15 7 44 2x153x152x12 2x15 8 44 1x10 9 44 2x153x202x15 10 44 2x20 2x151x15 11 33 1x202x201x20 12 22 1x20 1x10 PLYOCORE Mean Estimated Marginal MeanC.I. (95%)Mean Estimated Marginal MeanC.I. (95%) Partial ETA Squaredp SJ Height (m).2420.260.21, 0.25.2390.280.23, 0.28.180.07 SJ Average RFD (Ns-1)2078.682604.061884.11, 3324.013101.342575.961856.01, 3295.910.000.96 SJ Peak RFD (Ns-1)4687.115433.024214.51, 6651.526755.446009.544791.03, 7228.04.0250.52 SJ Peak Force (N)694.21769.63695.66, 843.60822.80747.38673.41, 821.35.0110.68 CMJ Height (m).26.2750.24, 0.31.270.260.23, 0.30.0190.57 CMJ Average RFD (Ns-1)2326.662581.031655.89, 3506.183144.162889.791964.64, 3814.93.0130.64 CMJ Peak RFD (Ns-1)5212.255516.504311.27, 6721.737125.516821.275616.04, 8026.50.120.12 CMJ Peak Force (N)685.68752.416700.66, 804.17843.43776.69724.94, 828.45.0260.51 Table 2: One-way between-groups analysis of covariance to determine differences in jumping performance after the intervention. RESULTS TRAINING TIMELINE Figure 1:Training timeline.