The relation between maximal voluntary force in m. palmaris longus and the temporal and spatial summation of muscle fiber recruitment in human subjects

Abstract

This study aimed at looking at the frequency (T‐score) and the amplitude (S‐score) of fiber use during contraction of a forearm muscle, m. palmaris longus, as measured by acoustic myography (AMG). An additional aim was to relate the T‐ and S‐scores to the recorded force obtained from a hand dynamometer. The hypothesis being that temporal and spatial summation of muscle fiber contraction in a given muscle during a given movement, can together describe a given obtained force. Force measurements were carried out on 12 healthy human subjects aged 19–68 years (6 men & 6 women), while their m. palmaris longus contractile function was measured using an acoustic myography CURO device. Force production was varied from 90 to 10% of assessed maximal voluntary force (MVF), and also monitored over a 1 min period of 50% MVF. Linear regression analysis was applied to relate force to spatial and temporal summation. Muscle strength was sustained by changing the frequency and/or the number of active fibere at any given point in time. Force production, whilst stronger for men than women, was regulated in a similar fashion for both sexes and was closely correlated with the AMG T‐ and S‐scores. It is concluded that AMG is a noninvasive method which can be readily applied to accurately describe how a subject uses a given muscle during any given movement. These findings have relevance when considering training strategies in subjects with muscle trauma or disease, in the elderly, or for both amateur and top professional athletes.

Acoustic Myography in Assessment of Isokinetic and Isometric Muscle Strength in a Healthy Danish Population

“…The data from the healthy AMG study [9] confirmed an earlier pilot study showing that muscle fibre recruitment (temporal and spatial summation) for a given type of force production is similar in men and women [11]. The study showed that the force produced by m. palmaris longus, although weaker for women than for men, was regulated identically for both genders and was closely correlated with the recorded AMG signal for this muscle [11]. The method applied in this study had the advantage over similar yet earlier methods, such as those used by Stokes and Blythe [12] and Madeleine [13], in that the sensors had a vastly improved frequency response, thereby providing a true image of muscle fibre use.…”

“…The method differs from surface electromyography (sEMG), since it measures the pressure waves generated by activated muscles rather than their electrical depolarization, thus avoiding the influence of neuromuscular endplates, which confound the sEMG signal [10]. The data from the healthy AMG study [9] confirmed an earlier pilot study showing that muscle fibre recruitment (temporal and spatial summation) for a given type of force production is similar in men and women [11]. The study showed that the force produced by m. palmaris longus, although weaker for women than for men, was regulated identically for both genders and was closely correlated with the recorded AMG signal for this muscle [11].…”

“…50 healthy subjects participated. The number of subjects was decided based on a Power calculation on previously published data [11,14], revealing a power of approximately 80% for this number of subjects in each age group. The age group was 20 -69 years, with 5 men and 5 women in each age decade.…”

A non-Invasive Assessment of Ground Reaction Forces in the Human Leg in Response to Walking, Jogging, Running and Jumping

“…Acoustic myography (AMG) is a biomechanical method measuring generated pressure waves from a contracting muscle [9] [10]. AMG recordings were carried out with a CURO unit and CURO sensors (CURO-Diagnostics ApS, Denmark; formerly MyoDynamikApS) and followed in real time on an iPADAir (Apple Inc., Cupertino, CA, USA) via the App "CURO Clinic" and a specialized data recording system.…”

“…Recorded data was stored to the CURO Unit and after completion of measurements transferred to the CURO software (https://app.myodynamik.com). The ESTi-score with its three components: 1) efficiency (E-score) 2) temporal fibre recruitment (T-score) and 3) spatial fibre recruitment (S-score), was calculated using the company software [9] [10].…”