Muscle activation strategies during strength training with heavy loading vs. repetitions to failure.
ABSTRACT Going to failure, or not, has probably been one of the most debated issues during the history of strength training. However, few studies have directly compared the physiological effect of failure vs. nonfailure strength training. The purpose of this study was to evaluate muscle activation strategies with electromyography (EMG) during heavy repetitions vs. repetitions to failure with lighter resistance. Fifteen healthy untrained women performed a set with heavy loading (3 repetition maximum [RM]) and a set of repetitions to failure with lower resistance (∼15 RM) during lateral raise with elastic tubing. Electromyographic amplitude and median power frequency of specific shoulder and neck muscles were analyzed, and the BORG CR10 scale was used to rate perceived loading immediately after each set of exercise. During the failure set, normalized EMG was significantly lower during the first repetition and significantly higher during the latter repetitions compared with the heavy 3-RM set (p < 0.05). Normalized EMG for the examined muscles increased throughout the set to failure in a curvilinear fashion--e.g., for the trapezius from 86 to 124% maximal voluntary contraction (p < 0.001)--and reached a plateau during the final 3-5 repetitions before failure. Median power frequency for all examined muscles decreased throughout the set to failure in a linear fashion, indicating progressively increasing fatigue. In conclusion, going to complete failure during lateral raise is not necessary to recruit the entire motor unit pool in untrained women--i.e., muscle activity reached a plateau 3-5 repetitions from failure with an elastic resistance of approximately 15 RM. Furthermore, strengthening exercises performed with elastic tubing seem to be an efficient resistance exercise and a feasible and practical alternative to traditional resistance equipment.
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ABSTRACT: PURPOSE: This study compared endurance and neuromuscular function after bouts of low-load (LL), high-load (HL) and low-load blood flow restricted (LLBFR) resistance exercise. METHODS: Eight recreationally active male subjects completed 3 sets of dynamic knee extensions to volitional failure under three conditions: HL (70% peak torque), LL (20% peak torque), and LLBFR (20% peak torque with an occlusive cuff inflated to 180 mmHg wrapped around the thigh). Before and immediately following exercise, isometric torque, central activation, electrically evoked torque and muscle activation via surface electromyography (EMG) were measured. RESULTS: Isometric torque and evoked torque decreased an average of 37% and 40%, respectively (P < 0.01) in all conditions following exercise. There were no differences in the toque decrements between the conditions (P>0.05). Percent central activation did not change after any condition (P = 0.09). Rate of torque development declined an average of 26% after all three conditions (P=0.003) and rate of half-relaxation time was depressed by 48% after the HL condition (P=0.004) only. EMG amplitude was greater in the HL condition at the beginning and end of exercise compared to the LL and LLBFR conditions (P=0.001). At the end of exercise, EMG amplitude rose 19% (P=0.02) and was not different among conditions (P>0.05). Subjects performed more repetitions during the LL and LLBFR conditions (P<0.05). CONCLUSION: Although LL and LLBFR resistance exercise to volitional failure exhibit lower levels of muscle activation than HL exercise, similar torque decrements occur after all bouts of resistance exercise and the muscle fatigue can be attributed to peripheral factors.Medicine and science in sports and exercise 08/2012; 45(1). DOI:10.1249/MSS.0b013e31826c6fa8 · 4.46 Impact Factor
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ABSTRACT: While elastic resistance training, targeting the upper body is effective for strength training, the effect of elastic resistance training on lower body muscle activity remains questionable. The purpose of this study was to evaluate the EMG-angle relationship of the quadriceps muscle during 10-RM knee-extensions performed with elastic tubing and an isotonic strength training machine. 7 women and 9 men aged 28-67 years (mean age 44 and 41 years, respectively) participated. Electromyographic (EMG) activity was recorded in 10 muscles during the concentric and eccentric contraction phase of a knee extension exercise performed with elastic tubing and in training machine and normalized to maximal voluntary isometric contraction (MVC) EMG (nEMG). Knee joint angle was measured during the exercises using electronic inclinometers (range of motion 0-90°). When comparing the machine and elastic resistance exercises there were no significant differences in peak EMG of the rectus femoris (RF), vastus lateralis (VL), vastus medialis (VM) during the concentric contraction phase. However, during the eccentric phase, peak EMG was significantly higher (p<0.01) in RF and VM when performing knee extensions using the training machine. In VL and VM the EMG-angle pattern was different between the two training modalities (significant angle by exercise interaction). When using elastic resistance, the EMG-angle pattern peaked towards full knee extension (0°), whereas angle at peak EMG occurred closer to knee flexion position (90°) during the machine exercise. Perceived loading (Borg CR10) was similar during knee extensions performed with elastic tubing (5.7±0.6) compared with knee extensions performed in training machine (5.9±0.5). Knee extensions performed with elastic tubing induces similar high (>70% nEMG) quadriceps muscle activity during the concentric contraction phase, but slightly lower during the eccentric contraction phase, as knee extensions performed using an isotonic training machine. During the concentric contraction phase the two different conditions displayed reciprocal EMG-angle patterns during the range of motion. 5.12/2012; 7(6):606-16.
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ABSTRACT: INTRODUCTION: Exercise programmes are used in the prevention and treatment of adductor-related groin injuries in soccer; however, there is a lack of knowledge concerning the intensity of frequently used exercises. OBJECTIVE: Primarily to investigate muscle activity of adductor longus during six traditional and two new hip adduction exercises. Additionally, to analyse muscle activation of gluteals and abdominals. MATERIALS AND METHODS: 40 healthy male elite soccer players, training >5 h a week, participated in the study. Muscle activity using surface electromyography (sEMG) was measured bilaterally for the adductor longus during eight hip adduction strengthening exercises and peak EMG was normalised (nEMG) using an isometric maximal voluntary contraction (MVC) as reference. Furthermore, muscle activation of the gluteus medius, rectus abdominis and the external abdominal obliques was analysed during the exercises. RESULTS: There were large differences in peak nEMG of the adductor longus between the exercises, with values ranging from 14% to 108% nEMG (p<0.0001). There was a significant difference between legs in three of the eight exercises (35-48%, p<0.0001). The peak nEMG results for the gluteals and the abdominals showed relatively low values (5-48% nEMG, p<0.001). CONCLUSIONS: Specific hip adduction exercises can be graded by exercise intensity providing athletes and therapists with the knowledge to select appropriate exercises during different phases of prevention and treatment of groin injuries. The Copenhagen Adduction and the hip adduction with an elastic band are dynamic high-intensity exercises, which can easily be performed at any training facility and could therefore be relevant to include in future prevention and treatment programmes.British Journal of Sports Medicine 03/2013; 48(14). DOI:10.1136/bjsports-2012-091746 · 5.03 Impact Factor