Effect of strength training on regional hypertrophy of the elbow flexor muscles

Regional Hypertrophy: The Effect of Exercises at Long and Short Muscle Lengths in Recreationally Trained Women

The aim of the present study was to analyse the role of exercises' resistance profile in regional hypertrophy. Thirty-eight healthy women completed a 9-week resistance training program consisting of either 4 sets of 12 repetitions to volitional failure of inclined bicep curls (INC group) or preacher curls (PREA group), three times per week. Pre- and post-intervention muscle thickness was measured using B-mode ultrasound imaging with a linear-array transducer. Scan acquisition sites were determined by measuring 50%, 60% and 70% of the distance between the posterior crest of the acromion and the olecranon. Statistical significance was set at p < 0.05. No region of the INC group grew when comparing pre- to post-intervention. The 70% region of the PREA group grew significantly (muscle thickness increased from 2.7 ± 0.43 cm to 2.94 ± 0.44 cm). We found no growth differences between regions when analysing per group (p = 0.274), region (p = 0.571) or group*region (p = 0.367). Our results show that the distal region of the arm grows in response to the preacher curl that places the highest amount of strain in the range of motion in which the arm muscles are more elongated.

Effects of Local Vibration on Dynamic Strength Training

ABSTRACT

Drummond, MDM, Couto, BP, Oliveira, MP, and Szmuchrowski, LA. Effects of local vibration on dynamic strength training. J Strength Cond Res 35(11): 3028-3034, 2021-The study aim was to compare the chronic effects of maximal dynamic strength training with and without the addition of local vibration (LV) on maximal force generation and hypertrophy of the elbow flexor muscles in trained subjects. Twenty men were divided into 2 groups (conventional training [CT] group and vibration training [VT] group). The CT group performed conventional maximal dynamic strength training, and the VT group performed maximal dynamic strength training with mechanical vibrations (frequency of 26 Hz and amplitude of 6 mm). CT and VT groups performed 5 sets of 3-4 repetitions, with 2-minute rest intervals between sets. The subjects trained 3 times per week for 12 weeks. After the training period, the CT group presented a significant increase in the mean 1 repetition maximum (1RM) value in the elbow flexion exercise in the orthostatic position (EFO) (7.2 ± 1.5%) (p < 0.0001) and elbow flexion exercise using the Scott bench (EFSB) (6.3 ± 1.8%) (p < 0.0001). The VT group also showed significant increases in 1RM values in the EFO (6.87 ± 0.8%) (p < 0.0001) and EFSB (6.56 ± 1.4%) (p < 0.0001). The CT group presented a significant increase in the mean maximal voluntary isometric contraction (MVIC) value after the training period (8.2 ± 2.3%) (p < 0.0001). The VT group also showed a significant increase in the mean MVIC value after training (9.1 ± 2.4%) (p < 0.0001). After the training period, both groups presented a significant increase in the mean value of elbow flexor thickness (CT = 5.6 ± 3.5%, VT = 5.1 ± 2.8%) (p = 0.001). The increases in 1RM, MVIC, and muscle thickness were statically similar between groups. Therefore, the addition of LV does not represent an additional stimulus for individuals trained in dynamic maximal strength training.

Evidenz von Trainingsempfehlungen für ein Hypertrophietraining

Der Abbau der Skelettmuskulatur steigt mit zunehmendem Alter und wird in der heutigen Gesellschaft aufgrund geringerer körperlicher Aktivität zusätzlich beschleunigt. Die Skelettmuskulatur ist vor allem für die Übertragung von Kräften und somit für unsere alltäglichen Bewegungen verantwortlich. Mit der Reduzierung der Muskelmasse wird die Durchführung von Alltagsbewegungen kontinuierlich erschwert, und die Lebensqualität kann dadurch deutlich sinken. Mit Kraft- bzw. Hypertrophietraining kann jedoch einer Muskelatrophie entgegengewirkt werden, indem Abbauprozesse verlangsamt werden und die Skelettmuskulatur wieder aufgebaut wird. Trainingsempfehlungen für ein Hypertrophietraining variieren jedoch erheblich. Dieser Artikel soll vor allem den aktuellen Forschungstand zusammenfassen und praxisrelevante Empfehlungen aussprechen.

Der entscheidendste Aspekt beim Hypertrophietraining scheint lediglich das Setzen von regelmäßigen progressiven und erschöpfenden Belastungsreizen zu sein, die mindestens einen Wirkungsmechanismus aktivieren, der für hypertrophe Effekte verantwortlich ist. Vor allem die Variation der mechano-biologischen Deskriptoren (Trainingswiderstand, Anzahl Wiederholungen und Sätze, Pause etc.) könnte helfen, langfristig effektive Reize zu gestalten. Dabei kann nahezu auf unbegrenzte Kombinationsmöglichkeiten zurückgegriffen werden, welche jedoch dem Leistungsniveau und der Belastbarkeit der trainierenden Person sowie der Umsetzbarkeit im Alltag angepasst werden müssen. Nach dem Motto „viele Wege führen nach Rom“ gibt es dabei nicht nur eine konkrete Lösung bei der Planung und Durchführung eines Hypertrophietrainings. Es ist eher von essenzieller Bedeutung, dass kontinuierliche Belastungsreize in unterschiedlichen Variationen durchgeführt werden, um einen Hypertrophieeffekt zu erzeugen und folglich dem Abbau der Skelettmuskulatur entgegenzuwirken.

Emphasizing Task-Specific Hypertrophy to Enhance Sequential Strength and Power Performance

While strength is indeed a skill, most discussions have primarily considered structural adaptations rather than ultrastructural augmentation to improve performance. Altering the structural component of the muscle is often the aim of hypertrophic training, yet not all hypertrophy is equal; such alterations are dependent upon how the muscle adapts to the training stimuli and overall training stress. When comparing bodybuilders to strength and power athletes such as powerlifters, weightlifters, and throwers, while muscle size may be similar, the ability to produce force and power is often inequivalent. Thus, performance differences go beyond structural changes and may be due to the muscle's ultrastructural constituents and training induced adaptations. Relative to potentiating strength and power performances, eliciting specific ultrastructural changes should be a variable of interest during hypertrophic training phases. By focusing on task-specific hypertrophy, it may be possible to achieve an optimal amount of hypertrophy while deemphasizing metabolic and aerobic components that are often associated with high-volume training. Therefore, the purpose of this article is to briefly address different types of hypertrophy and provide directions for practitioners who are aiming to achieve optimal rather than maximal hypertrophy, as it relates to altering ultrastructural muscular components, to potentiate strength and power performance.

Partial Compared with Full Range of Motion Resistance Training for Muscle Hypertrophy: A Brief Review and an Identification of Potential Mechanisms

Newmire, DE and Willoughby, DS. Partial compared to full range of motion resistance training for muscle hypertrophy: A brief review and an identification of potential mechanisms. J Strength Cond Res 32(9): 2661-2673, 2018-Resistance training promotes skeletal muscle hypertrophy; there are specific recommendations of intensity, volume, and duration that appear to facilitate hypertrophy the greatest. However, currently, there is not a definitive consensus on optimal range of motion. It appears that the partial range of motion (pROM) mode of exercise may have some similar benefit on muscle hypertrophy as the conventional full range of motion (fROM). Because of the dynamic and multiplanar movement pattern of a multijoint resistance exercise, there may be variation in human force-length and strength-curve theories, which may influence optimal muscle force production at differing portions of a fROM. This suggests specific muscle groups may potentially be optimally recruited during a specific portion of the exercise. The majority of previous research has primarily focused on strength outcomes opposed to muscle hypertrophy. The purpose of this brief review is to highlight the limited and relative pROM literature on muscle hypertrophy and some potential pROM mechanisms that require investigation to assess any plausible relationships. Some potential mechanisms and outcomes of interest are muscle time under tension, muscle activation, and nonuniform hypertrophy. This mode of resistance exercise requires further evaluation on hypertrophic responses; if proven efficacious, it may be employed to those in rehabilitative environments and those that seek more specific regional, local hypertrophic responses such as physique competitors.