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Updated: May 27, 2026
Ex Vivo Assessment of Contractility, Fatigability and Alternans in Isolated Skeletal Muscles
Published on: November 1, 2012
Responses of different types of ox muscle to electrical stimulation
C E Devine1, S Ellery, S Averill
1Meat Industry Research Institute of New Zealand (Inc.), PO Box 617, Hamilton, New Zealand.
Abstract:
The effects of electrical stimulation on fall in pH upon stimulation (ΔpH), rate of pH fall (dpH/dt at 35°C, cold shortening and muscle ultrastructure were investigated for the Cutaneus trunci (predominantly fast-twitch glycolytic fibres), the Masseter and Diaphragm (predominantly slow-twitch oxidative fibres) and the Sternomandibularis and Longissimus dorsi (bot fast- and slow-twitch fibres) of the ox. The Masseter and Diaphragm showed a small ΔpH and no increase in dpH/dt upon stimulation. Stimulation produced supercontracture but no tearing of the fibres throughout all of the Masseter. Stimulation of the Cutaneus trunci resulted in a significantly increased ΔpH and dpH/dt, loss of glycogen, mitochondrial swelling but no gross sarcomere changes. The Longissimus dorsi and Sternomandibularis had a moderate ΔpH and an increase in dpH/dt intermediate between that of the Masseter and the Cutaneus trunci. The Longissimus dorsi showed supercontracture, but the Sternomandibularis did not. Cold shortening responses at 2°C and 0°C were virtually unaffected by stimulation, being greatest in the Masseter and Diaphragm and least in the Cutaneus trunci. All muscles showed significantly greater shortenings at 0°C than 2°C. Stimulation of the Cutaneus trunci did not affect the tenderness of the cooked meat, but the toughness increased dramatically in cold-shortened Cutaneus muscle, regardless of stimulation. The Cutaneus trunci least requires stimulation as it does not cold shorten appreciably and therefore early rigor would confer no advantage. The Masseter and Diaphragm have a fast dpH/dt and therefore would enter rigor early. Mixed muscles apparently have the combined, least desirable characteristics of the muscle fibre types-i.e. their rate of rigor development is slow and they cold shorten. Electrical stimulation confers a significant advantage by mitigating these mixed-muscle characteristics in carcass muscles.
Insights
Electrical stimulation impacts beef muscle pH and texture differently based on fiber type. While beneficial for mixed-fiber muscles, it offers less advantage for fast-glycolytic or slow-oxidative muscles regarding cold shortening and meat tenderness.
Area of Science:
- Meat Science
- Animal Science
- Muscle Physiology
Background:
- Electrical stimulation is used to improve meat quality.
- Different bovine muscles have varying fiber compositions (fast-twitch glycolytic, slow-twitch oxidative, mixed).
- Understanding muscle response to stimulation is key for optimizing meat processing.
Purpose of the Study:
- To investigate the effects of electrical stimulation on pH decline, cold shortening, and ultrastructure in various ox muscles.
- To correlate muscle fiber type with responses to electrical stimulation and cold temperatures.
- To determine the practical implications of electrical stimulation for meat tenderness and quality.
Main Methods:
- Electrical stimulation applied to bovine Cutaneus trunci, Masseter, Diaphragm, Sternomandibularis, and Longissimus dorsi muscles.
- Measurement of pH fall (ΔpH) and rate of pH fall (dpH/dt) at 35°C.
- Assessment of cold shortening at 2°C and 0°C.
- Evaluation of muscle ultrastructure and meat tenderness/toughness post-cooking.
Main Results:
- Slow-twitch oxidative muscles (Masseter, Diaphragm) showed minimal pH change but significant supercontracture.
- Fast-twitch glycolytic muscle (Cutaneus trunci) exhibited increased ΔpH and dpH/dt, glycogen loss, and mitochondrial swelling.
- Mixed-fiber muscles (Longissimus dorsi, Sternomandibularis) had intermediate pH responses, with Longissimus dorsi showing supercontracture.
- Cold shortening was greatest in Masseter and Diaphragm, least in Cutaneus trunci, and unaffected by stimulation.
- Stimulation did not improve tenderness in Cutaneus trunci; cold shortening increased toughness.
Conclusions:
- Electrical stimulation is most advantageous for mixed-fiber muscles, mitigating undesirable traits like slow rigor development and cold shortening.
- Fast-glycolytic muscles require less stimulation due to minimal cold shortening.
- Slow-oxidative muscles with fast pH decline benefit less from stimulation regarding cold shortening prevention.
- Stimulation effectively alters pH and ultrastructure, but its impact on tenderness varies significantly with muscle fiber type and cold exposure.
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