augmented eccentric loading study
DESCRIPTION
Augmented Eccentric Loading StudyTRANSCRIPT
The effects of augmented eccentric loading on force andpower production during the countermovement jump
G. Sapstead, P.H. Watkins, L. Griffiths, J. Lees and A. CulleyDepartment of Sport and Exercise Science, University of Derby, Kedleston Road UK
Discussion
The purpose of this study was to examine the acute effects of AEL during the box squat exercise (BSE), using a loadingstrategy for enhancing power production, on subsequent countermovement jump (CMJ) performance. No significantdifferences were found on either PF, PP or PRFD with the use of AEL over traditional training methods, however thiswas not the case for all subjects. The highest peak power among subjects was actually observed during the AELcondition, despite the mean values for PF, PP and PRFD among conditions appearing higher in the 50/50 condition.These results may suggest that augmented eccentric load thresholds for optimal power production may differ betweenindividuals, and in order for an enhanced concentric power production, and possible neural excitation of the loadedmuscles to occur in the BSE, individual load selection may need to be considered (Ojasto and Hakkinen, 2009).
Possible explanations for enhanced concentric force output due to AEL could be explained by increases in neuralstimulation, contractile machinery alterations, recovery of stored elastic energy, and increased preload (Moore andSchilling, 2005, Ojasto and Hakkinen 2009). In order for these mechanisms to take place and positively enhancesubsequent exercise performance, differing loading strategies need to be considered that take into account the varioustraining qualities that are being targeted through training (i.e. hypertrophy ~90%; strength ~105-120%; power ~70-80% 1-RM), however this is still an area of much debate. As previously suggested, there exists little research orguidelines regarding optimal loading strategies to enhance both acute and chronic adaptations to AEL. More researchusing multiple eccentric-concentric specific loads across populations is needed to confirm if such thresholds exist.
ReferencesBrandenburg, JP and Docherty, D (2002). The effects of accentuated eccentric loading on strength, muscle hypertrophy, and neural adaptations in trained individuals. Journal of Strength andConditioning Research. 16(1): 25-32.Doan, B., Fry, A., Korziris, L., Kraemer, W., Marsit, J., Newton, R and Triplett-McBride, N (2002). Effects of increased eccentric loading on bench press 1-RM. Journal of Strength and ConditioningResearch. 16(1):9-13.Moore, C.A and Schilling, B.K (2005). Theory and application of augmented eccentric loading. Strength and Conditioning Journal. 27(5): 20-27.Moore, C.A., Weiss, L.W., Schilling, B.K., Fry, A.C and Yuhua, L (2007). Acute effects of augmented eccentric loading on jump squat performance. Journal of Strength and ConditioningResearch. 21(2): 372-377.Ojasto, T and Hakkinen, K (2009). Effects of different accentuated eccentric loads on acute neuromuscular, growth hormone, and blood lactate responses during a hypertrophic protocol. Journal of Strength and Conditioning Research. 23(3): 946-953.Ojasto, T and Hakkinen, K (2009). Effects of different accentuated eccentric load levels in eccentric-concentric actions on acute neuromuscular, maximal force, and power responses.Journal of Strength and Conditioning Research. 23(3): 996-1004.Watkins, P.H (2010). Augmented Eccentric Loading: Theoretical and Practical Applications for the Strength and Conditioning Professional. Professional Strength and Conditioning. In Press.
Introduction
The practice of incorporating augmented eccentric loading (AEL) into resistance exercise is still relatively new, althoughlimited, there is evidence supporting the contention that AEL may lead to both acute (Doan et al, 2002) and chronic(Brandenburg and Docherty, 2002) strength training adaptations over more traditional methods. Although the body ofliterature on AEL has yielded mostly positive results regarding its use for developing strength and power, someresearchers have demonstrated there to be no advantages with the use of AEL over traditional strength and powertraining methods (Moore et al, 2007).
Although no conclusive statement can be made with regards to optimal eccentric-concentric load selection for bothacute or chronic concentric performance enhancement, superior gains in strength, power and hypertrophy may beachieved when eccentric loads are in excess of the concentric 1-RM (i.e., hypertrophy ~90%; strength ~105-120%;power ~70-80%), and when the optimal eccentric load is approximately 20% greater than the concentric load(Watkins, 2010). Ojasto and Hakkinen (2009) also recently demonstrated an increase in bench press peak power overtraditional loading conditions when a 50% concentric load was used with an approximately 20% greater eccentric load.
The aim of this study was to therefore examine whether AEL of the box squat exercise (BSE) with a loading strategytargeting power development, would acutely enhance concentric force and power output during subsequentcountermovement jump (CMJ) performance.
Methods
Participants Following ethical approval and informed consent, seven healthy university sport and exercise science students (Table 1)were used as participants for this study. Prior to testing, participants 1-RMs for the BSE were established, from whichthe percentages of loading were calculated for the experimental conditions.
ProceduresParticipants completed a warm up, consisting of upper and lower body dynamic stretches. three testing sessions werecompleted under the following conditions:
Condition 1: Baseline measures were established via the use of a force plate (400 Series, Fittech, Australia), witha sampling frequency of 500Hz, where measurements of Peak Power (PP), Peak Force (PF) and Rate of ForceDevelopment (RFD) were established.
Condition 2: (50/50% 1-RM eccentric/concentric): Participants performed three cluster repetitions with 15 secondinter-repetition rest intervals, with 50% of 1-RM on both the eccentric and concentric phase of the BSE. This wasfollowed by 2.5 minutes rest prior to performing CMJs.
Condition 3: (70/50% 1-RM eccentric/concentric): Participants performed three cluster repetitions with 15 secondinter-repetition rest intervals, with 70% of 1-RM on the eccentric and 50% 1-RM on the concentric phase of the BSE,followed by 2.5 minutes rest prior to performing CMJs. CMJs were performed a total of three times, allowing fora rest period of three minutes between each maximal effort. Sessions were conducted 72 hours apart to account forthe effects of fatigue.
Statistical AnalysisAny changes in PF, PP and PRFD were analyzed using a 3 (conditions) x 1 way repeated measures ANOVA. Statisticalanalysis was performed using the Statistical Package for Social Sciences (SPSS v 16.0, Chicago, USA). Significance wasaccepted at p<0.05.
Results
Results from the one way repeated measures ANOVA indicated no significant differences (p>0.05) between measuresof peak concentric power across all loading conditions, with the highest mean values demonstrated in Condition 2(Figure 5). Although the highest peak power between subjects was observed during the 70/50% loading condition.Peak concentric force values were also highest in Condition 2 (Figure 6), however these were not significant (p>0.05).No significant differences (p>0.05) in peak rate of force development were witnessed across conditions, though thehighest mean value was demonstrated in Condition 2 (Figure 7).
Table 1: Subject descriptive data obtained prior to loaded testing conditions
Age (yrs) Height (cm) Body Mass (Kg)
Mean 23.8 173.8 75.3
S.D. ±9.1 ±14.1 ±40.6
Figure 1: AEL setup and starting position (frontal plane).The placement of the second set of collars and green (10kg)discs on the barbell may be used as an effective alternativeto weight releasers.
Figure 2: Seated position on the box after the eccentric phaseof the squat (frontal plane).
Figure 3: Seated position on the box after the eccentric phaseof the squat (frontal plane). Note: the green discs have nowbeen removed from the bar simultaneously by two spotters.
Figure 4: Finishing position at the end of the concentric phaseof the BSE. Note: the load used during the concentric phase islighter than that during the eccentric phase.
Table 2: Mean ± S.D. of Peak Force, Peak Power and Peak Rate of Force Development (PRFD) acrossloading conditions
Condition 1 Condition 2 Condition 3
Peak Force (N) 2899 ± 936 3761 ± 1925 3366 ± 1530
Peak Power (W) 10060 ± 5076 13198 ± 5035 12912 ± 4878
PRFD (N/s) 53115 ± 37916 69180 ± 49903 66785 ± 42533
Figure 5: Mean ± S.D. of Peak Force obtained for the CMJ across loading conditions
Peak Force
Peak Power
Peak Rate of Force Development
Figure 6: Mean ± S.D. of Peak Power obtained for the CMJ across loading conditions
Figure 7: Mean ± S.D. of PRFD obtained for the CMJ across conditions
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