Repeatability and Specificity of Eccentric Force Output and the Implications for Eccentric Training Load Prescription.

Harden, M, Wolf, A, Haff, GG, Hicks, KM, and Howatson, G. Repeatability and specificity of eccentric force output and the implications for eccentric training load prescription. J Strength Cond Res 33(3): 676-683, 2019-Prescribing supramaximal eccentric (ECC) loads based on repetition maximum, isometric (ISO), or concentric-only (CON) strength overlooks the possibility that individuals have a different tolerance for ECC exercise. To inform the prescription of ECC training regimes, this study implemented a test battery that included maximal accentuated-eccentric (ECC+), traditional coupled eccentric-concentric (TRAD), and 2 ISO conditions (90 and 120° knee-joint angle [ISO90 and ISO120, respectively]). The study aimed to determine the repeatability and specificity of ECC+ force output and assess the methodological accuracy when using nonspecific measures of strength to prescribe ECC+ training loads. Results show that the test battery was repeatable (p > 0.05, intraclass correlation coefficient >0.95, coefficient of variation: <5.8%) and force output was specific to each task; ECC+ (4,034 ± 592 N) was higher (p < 0.001) than ISO90 (3,122 ± 579 N) and TRAD (3,574 ± 581 N), but less (p < 0.001) than ISO120 (6,285 ± 1,546 N). Although estimations of ECC+ strength were not different from observed ECC+ values (p > 0.05), estimations were associated with up to a 7% error. This investigation confirms that force output is task-specific; therefore, prescribing ECC loads based on strength during another task will likely lead to discrepancies in intended and actual ECC exercise intensity. Consequently, using an ECC-specific approach to assess ECC strength qualities will provide a more accurate platform to prescribe individualized ECC training programs and a more definitive evaluation of ECC strength.

An Evaluation of Supramaximally Loaded Eccentric Leg Press Exercise.

Harden, M, Wolf, A, Russell, M, Hicks, KM, French, D, and Howatson, G. An evaluation of supramaximally loaded eccentric leg press exercise. J Strength Cond Res 32(10): 2708-2714, 2018-High-intensity eccentric exercise is a potent stimulus for neuromuscular adaptation. A greater understanding of the mechanical stimuli afforded by this exercise will aid the prescription of future eccentric training regimens. This study sought to investigate the mechanical characteristics of supramaximally loaded eccentric exercise when using a custom-built leg press machine. Using a within-subject, repeated-measures design, 15 strength trained subjects (age, 31 ± 7 years; height, 180.0 ± 6.8 cm; body mass, 81.5 ± 13.9 kg) were assessed under 3 different conditions: low (LO), moderate (MOD), and high (HI) intensity, which were equivalent in intensity to 110, 130, and 150%, respectively, of peak force during an isometric maximal voluntary contraction (IMVC) performed on leg press at 90° knee flexion. All loading conditions demonstrated a similar pattern of mechanical profile; however, the variables underpinning each profile showed significant (p < 0.01) load-dependent response (LO vs. MOD, MOD vs. HI, LO vs. HI) for all variables, except for average acceleration. Average force associated with each loading conditions exceeded IMVC but equated to a lower intensity than what was prescribed. Repetitions under higher relative load intensity stimulated greater average force output, faster descent velocity, greater magnitude of acceleration, shorter time under tension, and a decline in force output at the end range of motion. This research provides new data regarding the fundamental mechanical characteristics underpinning supramaximally loaded eccentric leg press exercise. The information gathered in the study provides a foundation for practitioners to consider when devising loading strategies and implementing or evaluating supramaximally loaded eccentric exercise when using a similar exercise and device.

Four weeks of augmented eccentric loading using a novel leg press device improved leg strength in well-trained athletes and professional sprint track cyclists.

This study assessed the efficacy of strength training using augmented eccentric loading to provoke increases in leg strength in well-trained athletes, and sprint track cyclists, using a novel leg press device. Twelve well-trained athletes were randomly allocated traditional resistance training (TRAD, n = 6), or resistance training using augmented eccentric loading (AEL, n = 6). A further 5 full-time, professional sprint track cyclists from a senior national squad programme also trained with augmented eccentric loading (AEL-ATH) alongside their usual sport-specific training. Participants completed four weeks of twice-weekly resistance training using the leg press exercise. In TRAD the lowering phase of the lift was set relative to concentric strength. In AEL and AEL-ATH the lowering phase was individualised to eccentric strength. Concentric, eccentric, isometric and coupled eccentric-concentric leg press strength, and back squat 1 repetition maximum (1RM), were assessed pre- and post-training. The AEL and AEL-ATH groups performed the eccentric phase with an average 26 ± 4% greater load across the programme. All groups experienced increases in concentric (5%, 7% and 3% for TRAD, AEL & AEL-ATH respectively), eccentric (7%, 11% and 6% for TRAD, AEL & AEL-ATH respectively), and squat 1RM (all p < 0.05), where the AEL-ATH group experienced relatively greater increases (13% vs. 5% in TRAD and AEL, p < 0.01). The TRAD and AEL groups also increased isometric strength (p < 0.05). A four-week period of augmented eccentric loading increased leg strength in well-trained athletes and track cyclists. The eccentric leg press stimulus was well-tolerated, supporting the inclusion of such training in the preparation programmes of athletes.

Implementing Eccentric Resistance Training-Part 1: A Brief Review of Existing Methods.

The purpose of this review was to provide a physiological rationale for the use of eccentric resistance training and to provide an overview of the most commonly prescribed eccentric training methods. Based on the existing literature, there is a strong physiological rationale for the incorporation of eccentric training into a training program for an individual seeking to maximize muscle size, strength, and power. Specific adaptations may include an increase in muscle cross-sectional area, force output, and fiber shortening velocities, all of which have the potential to benefit power production characteristics. Tempo eccentric training, flywheel inertial training, accentuated eccentric loading, and plyometric training are commonly implemented in applied contexts. These methods tend to involve different force absorption characteristics and thus, overload the muscle or musculotendinous unit in different ways during lengthening actions. For this reason, they may produce different magnitudes of improvement in hypertrophy, strength, and power. The constraints to which they are implemented can have a marked effect on the characteristics of force absorption and therefore, could affect the nature of the adaptive response. However, the versatility of the constraints when prescribing these methods mean that they can be effectively implemented to induce these adaptations within a variety of populations.

Implementing Eccentric Resistance Training-Part 2: Practical Recommendations.

The purpose of this review is to provide strength and conditioning practitioners with recommendations on how best to implement tempo eccentric training (TEMPO), flywheel inertial training (FIT), accentuated eccentric loading (AEL), and plyometric training (PT) into resistance training programs that seek to improve an athlete's hypertrophy, strength, and power output. Based on the existing literature, TEMPO may be best implemented with weaker athletes to benefit positional strength and hypertrophy due to the time under tension. FIT may provide an effective hypertrophy, strength, and power stimulus for untrained and weaker individuals; however, stronger individuals may not receive the same eccentric (ECC) overload stimulus. Although AEL may be implemented throughout the training year to benefit hypertrophy, strength, and power output, this strategy is better suited for stronger individuals. When weaker and stronger individuals are exposed to PT, they are exposed to an ECC overload stimulus as a result of increases in the ECC force and ECC rate of force development. In conclusion, when choosing to utilize ECC training methods, the practitioner must integrate these methods into a holistic training program that is designed to improve the athlete's performance capacity.