Effects of dynamic upper-body exercise on lower-limb isometric endurance

Abstract

Following preliminary indications that in some individuals arm exercise enhanced rather than reduced simultaneous leg endurance, ten young men and women performed three forms of intermittent work to volitional exhaustion, under duty cycles of 45 s work, 15 s rest. The protocols were as follows: (A) knee extensions at 30% maximum voluntary contraction (MVC); (B) 30% MVC knee extensions combined with arm cranking at 130% of their own lactate threshold; (C) combined 30% MVC knee extensions and arm cranking at 20% of their own lactate threshold. Heart rate, oxygen uptake ([Vdot]O₂), and blood lactate concentration were among the variables recorded throughout. All physiological indicators of demand were substantially higher in protocol B than in protocols A or C [heart rate: (A) 154 beats · min⁻¹, (B) 171 beats · min⁻¹, (C) 150 beats · min⁻¹; [Vdot]O₂: (A) 11.9 ml · kg⁻¹ · min⁻¹, (B) 21.7 ml · kg⁻¹ · min⁻¹, (C) 14.2 ml · kg⁻¹ · min⁻¹; blood lactate concentration: (A) 3.3 mmol · l⁻¹, (B) 5.1 mmol · l⁻¹, (C) 2.8 mmol · l⁻¹], yet there were no significant differences (P > 0.05) in the endurance times between the three conditions [(A) 11.43 min, (B) 11.1 min, (C) 10.57 min] and seven participants endured longest in protocol B. Results from protocol (C) cast doubt on explanations in terms of psychological distraction. We suggest that lactic acid produced by the arms is shuttled to the legs and acts there either as a supplementary fuel source or as an antagonist to the depressing effects of increased potassium concentration.

Keywords:

• Arm cranking
• dinghy sailing
• dynamic exercise
• endurance
• isometric exercise
• knee extension

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Corrigendum

Acknowledgements

Thanks are due to J. Sinclair and G. Baxter for design and construction of the electronic and mechanical equipment respectively, to R. Auld, P. Patterson, and I. Watt (and, in earlier years, H. Collin and J. Wilson) for technical assistance in the lab, and to Y. Pitsiladis for statistical advice and assistance. We gratefully acknowledge the permission of J. G. Gallacher, S. Gillen, G. Hunter, R. Wallace (class of 2000), and of S. Collins, J. McGrenary, T. O'Hare, M. C. Williamson, and F. Wood (class of 2001), for us to summarize the pertinent results of their BSc projects. We thank also the participants in all three series of experiments.