Effects of asymmetric load bench press offset training on muscle activation levels and exercise-induced fatigue in collegiate bodybuilders
ObjectiveThis study systematically investigated the effects of graded asymmetric load bench press offset training on muscle activation patterns, exercise-induced fatigue, and movement performance in bodybuilders.MethodsTen male athletes (age: 24.20 ± 1.91 years; 1 R M bench press: 120.00 ± 14.66 kg)...
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Frontiers Media S.A.
2025-05-01
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| Series: | Frontiers in Physiology |
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| Online Access: | https://www.frontiersin.org/articles/10.3389/fphys.2025.1592477/full |
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| author | Bin Yan Siqi Yao Junjie Zhang Chunwei Li Tongxin Han Qiushi Hu Kai Lv |
| author_facet | Bin Yan Siqi Yao Junjie Zhang Chunwei Li Tongxin Han Qiushi Hu Kai Lv |
| author_sort | Bin Yan |
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| description | ObjectiveThis study systematically investigated the effects of graded asymmetric load bench press offset training on muscle activation patterns, exercise-induced fatigue, and movement performance in bodybuilders.MethodsTen male athletes (age: 24.20 ± 1.91 years; 1 R M bench press: 120.00 ± 14.66 kg) underwent randomized crossover trials with 0% (symmetrical), 2%, 4%, and 6% asymmetric load interventions (70% 1 R M total load). Surface electromyography (sEMG) quantified activation levels of pectoralis major (PM), anterior deltoid (AD), triceps brachii (TB), and external oblique (EO), while barbell kinematics, blood lactate, and heart rate were analyzed to assess fatigue.ResultKey findings revealed significant interlimb asymmetry under symmetrical loading, with dominant-side PM (51 ± 6.82 vs 35 ± 5.32 MVIC%, p = 0.009) and AD (48.2 ± 5.05 vs 32.6 ± 9.21 MVIC%, p = 0.038) exhibiting higher activation than the non-dominant side. Asymmetric loading effectively mitigated this imbalance: 6% intervention increased non-dominant PM (54.4% ± 8.46% vs 0%: 35 ± 5.32 MVIC%, p = 0.035) and AD activation (52.3% ± 12.7% vs 0%: 32.6 ± 9.21 MVIC%, p = 0.022), but triggered compensatory EO recruitment (31.1% ± 12.3% vs 0%: 12.8 ± 3.34 MVIC%, p < 0.001). Performance metrics declined progressively with higher asymmetry: 6% loading reduced barbell velocity (MV: 0.28% ± 0.03% vs 0%: 0.38 ± 0.04 m/s, p < 0.001), repetitions (6.63% ± 2.40% vs 0%: 13.90 ± 2.52, p < 0.001), and power (MP: 357% ± 43% vs 0%: 437 ± 53.70 W, p = 0.009). Physiological fatigue markers intensified at 6% asymmetry, evidenced by elevated post-exercise blood lactate (7.42% ± 1.59% vs 0%: 9.88 ± 0.75 mmol/L, p = 0.003) and prolonged heart rate recovery.ConclusionThe study identifies 2%–4% asymmetric loading as optimal for enhancing non-dominant muscle activation while minimizing fatigue, whereas 6% interventions induce core compensation and performance deterioration. These findings establish evidence-based thresholds for precision training protocols, addressing interlimb asymmetry while balancing neuromuscular efficacy and physiological strain. Methodological innovations include multidimensional analysis of biomechanical, electromyographic, and physiological responses, advancing the understanding of neuromuscular coordination in asymmetric resistance training. |
| format | Article |
| id | doaj-art-ff7ff78574a441b4a964d21c0d74f50b |
| institution | OA Journals |
| issn | 1664-042X |
| language | English |
| publishDate | 2025-05-01 |
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| spelling | doaj-art-ff7ff78574a441b4a964d21c0d74f50b2025-08-20T02:28:20ZengFrontiers Media S.A.Frontiers in Physiology1664-042X2025-05-011610.3389/fphys.2025.15924771592477Effects of asymmetric load bench press offset training on muscle activation levels and exercise-induced fatigue in collegiate bodybuildersBin Yan0Siqi Yao1Junjie Zhang2Chunwei Li3Tongxin Han4Qiushi Hu5Kai Lv6Academic Affairs Office, Henan Sports University, Zhengzhou, Henan, ChinaSchool of Physical Education, Zhengzhou University (Main Campus), Zhengzhou, Henan, ChinaAcademic Affairs Office, Henan Sports University, Zhengzhou, Henan, ChinaAcademic Affairs Office, Henan Sports University, Zhengzhou, Henan, ChinaAcademic Affairs Office, Henan Sports University, Zhengzhou, Henan, ChinaKangda College, Nanjing Medical University, Nanjing, Jiangsu, ChinaDepartment of Physical Education, Tianjin Medical University, Tianjin, ChinaObjectiveThis study systematically investigated the effects of graded asymmetric load bench press offset training on muscle activation patterns, exercise-induced fatigue, and movement performance in bodybuilders.MethodsTen male athletes (age: 24.20 ± 1.91 years; 1 R M bench press: 120.00 ± 14.66 kg) underwent randomized crossover trials with 0% (symmetrical), 2%, 4%, and 6% asymmetric load interventions (70% 1 R M total load). Surface electromyography (sEMG) quantified activation levels of pectoralis major (PM), anterior deltoid (AD), triceps brachii (TB), and external oblique (EO), while barbell kinematics, blood lactate, and heart rate were analyzed to assess fatigue.ResultKey findings revealed significant interlimb asymmetry under symmetrical loading, with dominant-side PM (51 ± 6.82 vs 35 ± 5.32 MVIC%, p = 0.009) and AD (48.2 ± 5.05 vs 32.6 ± 9.21 MVIC%, p = 0.038) exhibiting higher activation than the non-dominant side. Asymmetric loading effectively mitigated this imbalance: 6% intervention increased non-dominant PM (54.4% ± 8.46% vs 0%: 35 ± 5.32 MVIC%, p = 0.035) and AD activation (52.3% ± 12.7% vs 0%: 32.6 ± 9.21 MVIC%, p = 0.022), but triggered compensatory EO recruitment (31.1% ± 12.3% vs 0%: 12.8 ± 3.34 MVIC%, p < 0.001). Performance metrics declined progressively with higher asymmetry: 6% loading reduced barbell velocity (MV: 0.28% ± 0.03% vs 0%: 0.38 ± 0.04 m/s, p < 0.001), repetitions (6.63% ± 2.40% vs 0%: 13.90 ± 2.52, p < 0.001), and power (MP: 357% ± 43% vs 0%: 437 ± 53.70 W, p = 0.009). Physiological fatigue markers intensified at 6% asymmetry, evidenced by elevated post-exercise blood lactate (7.42% ± 1.59% vs 0%: 9.88 ± 0.75 mmol/L, p = 0.003) and prolonged heart rate recovery.ConclusionThe study identifies 2%–4% asymmetric loading as optimal for enhancing non-dominant muscle activation while minimizing fatigue, whereas 6% interventions induce core compensation and performance deterioration. These findings establish evidence-based thresholds for precision training protocols, addressing interlimb asymmetry while balancing neuromuscular efficacy and physiological strain. Methodological innovations include multidimensional analysis of biomechanical, electromyographic, and physiological responses, advancing the understanding of neuromuscular coordination in asymmetric resistance training.https://www.frontiersin.org/articles/10.3389/fphys.2025.1592477/fullinterlimb asymmetryelectromyographyresistance trainingneuromuscular adaptationfatigue thresholdcore compensation |
| spellingShingle | Bin Yan Siqi Yao Junjie Zhang Chunwei Li Tongxin Han Qiushi Hu Kai Lv Effects of asymmetric load bench press offset training on muscle activation levels and exercise-induced fatigue in collegiate bodybuilders Frontiers in Physiology interlimb asymmetry electromyography resistance training neuromuscular adaptation fatigue threshold core compensation |
| title | Effects of asymmetric load bench press offset training on muscle activation levels and exercise-induced fatigue in collegiate bodybuilders |
| title_full | Effects of asymmetric load bench press offset training on muscle activation levels and exercise-induced fatigue in collegiate bodybuilders |
| title_fullStr | Effects of asymmetric load bench press offset training on muscle activation levels and exercise-induced fatigue in collegiate bodybuilders |
| title_full_unstemmed | Effects of asymmetric load bench press offset training on muscle activation levels and exercise-induced fatigue in collegiate bodybuilders |
| title_short | Effects of asymmetric load bench press offset training on muscle activation levels and exercise-induced fatigue in collegiate bodybuilders |
| title_sort | effects of asymmetric load bench press offset training on muscle activation levels and exercise induced fatigue in collegiate bodybuilders |
| topic | interlimb asymmetry electromyography resistance training neuromuscular adaptation fatigue threshold core compensation |
| url | https://www.frontiersin.org/articles/10.3389/fphys.2025.1592477/full |
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