Anna Cristina de Farias Marques*

anna.marques1309@gmail.com

Adriano Percival Calderaro Calvo**

percivalcalvo.fab@gmail.com

Daniel Tineu Leite Maia***

d_tineu@hotmail.com

Maysa Alves Rodrigues Brandão Rangel+

maysarangel_4@hotmail.com

Rodolfo Paula Vieira++

rodrelena@yahoo.com.br

Regiane Albertini Carvalho+++

regiane.albertini@unifesp.br

Flávio Aimbire Soares de Carvalho++++

flavio.aimbire@unifesp.br

*Ph.D. in Translational Medicine

Master's degree in Rehabilitation Science

Graduation in Physiotherapy Graduate Program in Translational Medicine

Federal University of São Paulo (UNIFESP)

**Graduation in Physical Education

Master’s degree in Motricity Science

Ph.D. in Science. Post doctorate in Exercise Science and Sport

He is Assistant Professor of Brazilian Air Force University (UNIFA)

in Graduate Program in Military Human Performance

Scientific Researcher at Aerospace Medical Institute (IMAE)

***Ph.D. in Translational Medicine

Master's degree in Biomedical Engineering

Graduation in Physiotherapy

+Ph.D. in Human Movement Science and Rehabilitation

Master's degree in Medicine; Graduation in Physiotherapy

++Graduation in Physical Education

Master's in Biological Sciences. Ph.D. in Pathology

Post doctorate in Physical Activity and Pulmonary Immunology

Post doctorate in ASMA Immunology

Supervisor in Graduate Program in Human Movement Science

and Rehabilitation at UNIFESP

+++Graduation at Physiotherapy

Master's and Ph.D. in Biomedical Engineering

Currently professor at Federal University of São Paulo (UNIFESP)

Director of Science and Technology Institute of UNIFESP

++++Graduation at Biological Science

Master's in Pharmacology. Ph.D. in Biomedical Engineering

Currently full professor at Federal University of São Paulo (UNIFESP)

Reception: 08/28/2023 - Acceptance: 10/30/2023

1st Review: 10/27/2023 - 2nd Review: 10/11/2023

Accessible document. Law N° 26.653. WCAG 2.0

Suggested reference: Marques, ACF, Calvo, APC, Maia, DTL, Rangel, MARB, Vieira, RP, Carvalho, RA, & Carvalho, FAS (2023). Forearm Muscle Activity and Handgrip Profile Between Physically Active and Sedentary Older Women. Lecturas: Educación Física y Deportes, 28(306), 107-122. https://doi.org/10.46642/efd.v28i306.7195

 

Abstract

    Background: The aging process promotes changes in skeletal muscles that influence muscle strength and fatigue, however physical exercise has a direct effect on the aging process. Objective: The aim of this study was investigated the strength and strength fatigability and the muscle activities of the forearm of elderly women’s handgrip according physical level. Method: The patterns of rapid muscle strength, maximum strength and fatigability of 32 elderly women during handgrip task were evaluated in this cross-sectional study. Both hands were evaluated and the muscle activity of the carpal flexors and extensors was monitored with an electromyography simultaneously. Volunteers were grouped into two groups based on their level of physical activity: physically active and sedentary. Results were compared by group and time factors. Results: Rapid muscle strength and maximum isometric strength were substantially higher in the physically active. Loss of strength was verified in physically active while the fatigue by muscle activity was identified in sedentary group. Discussion: The volunteers' physical activity pattern was able to change their muscle contraction strategies. The active group mainly practices strength training or combined training that includes strength training with at least 3 sessions per week. This volume was also enough to promote gains in the strength and rapid strength. Conclusion: The physical activity profile of the elderly women in this study have influenced strength, fatigability, and muscle activity during handgrip strength.

    Keywords: Aging. Hand strength. Muscle fatigue. Electromyography. Physical activity.

 

Resumen

    Introducción: El proceso de envejecimiento promueve cambios en los músculos esqueléticos que influyen en la fuerza muscular y la fatiga, pero el ejercicio físico tiene un efecto directo en el proceso de envejecimiento. Objetivo: Investigar la fuerza y la fatigabilidad de la fuerza de prensión del antebrazo y las actividades musculares en mujeres mayores dependiendo de su nivel de actividad física. Método: En este estudio transversal se evaluaron los patrones de fuerza muscular rápida, fuerza máxima y fatigabilidad de 32 mujeres mayores durante la fuerza de prensión manual. Se evaluaron ambas manos y se monitorizó simultáneamente la actividad electromiográfica de flexores y extensores del carpo. Los voluntarios se agruparon en dos grupos según su nivel de actividad física. Los resultados se compararon por factores de grupo y tiempo. Resultados: La fuerza muscular rápida y la fuerza isométrica máxima fueron sustancialmente mayores en el grupo activo. Se observó pérdida de fuerza en el grupo activo mientras que en el grupo inactivo se identificó fatiga debida a la actividad muscular. Discusión: El patrón de actividad física de los voluntarios logró cambiar sus estrategias de contracción muscular. El grupo activo practica principalmente entrenamiento de fuerza o entrenamiento combinado que incluye entrenamiento de fuerza con al menos 3 sesiones semanales. Este volumen también fue suficiente para promover un rápido aumento de fuerza y fuerza rápida. Conclusión: El perfil de actividad física de las mujeres mayores de este estudio influyó en la fuerza, la fatigabilidad y la actividad muscular durante la fuerza de prensión manual.

    Palabras clave: Envejecimiento. Fuerza de mano. Fatiga muscular. Electromiografía. Actividad física.

 

Resumo

    Introdução: O processo de envelhecimento promove alterações na musculatura esquelética que influenciam na força muscular e na fadiga, porém o exercício físico tem efeito direto no processo de envelhecimento. Objetivo: O objetivo deste estudo foi investigar a força e a fadigabilidade da força e as atividades musculares do antebraço de preensão manual de idosas de acordo com o nível de atividade física. Método: Os padrões de força muscular rápida, força máxima e fadigabilidade de 32 idosas durante a força de preensão manual foram avaliados neste estudo transversal. Ambas as mãos foram avaliadas, e a atividade muscular dos flexores e extensores do carpo foi monitorada por eletromiografia simultaneamente. Os voluntários foram agrupados em dois grupos com base no seu nível de atividade física. Os resultados foram comparados por fatores de grupo e tempo. Resultados: A força muscular rápida e a força isométrica máxima foram substancialmente maiores no grupo ativo. A perda de força foi verificada no grupo ativo enquanto a fadiga por atividade muscular foi identificada no grupo inativo. Discussão: O padrão de atividade física dos voluntários foi capaz de alterar suas estratégias de contração muscular. O grupo ativo pratica principalmente treino de força ou treino combinado que inclui treino de força com pelo menos 3 sessões por semana. Este volume também foi suficiente para promover ganhos de força e força rápida. Conclusão: O perfil de atividade física das idosas deste estudo influenciou a força, a fatigabilidade e a atividade muscular durante a força de preensão manual.

    Unitermos: Envelhecimento. Força da mão. Fadiga muscular. Eletromiografia. Atividade física.

 

Lecturas: Educación Física y Deportes, Vol. 28, Núm. 306, Nov. (2023)

---

 

Introduction 

 

    Extensive knowledge about the health benefits of physical exercise is not enough to massively attract elderly people to physical practices, nor to keep them physically active for a long period of time (Goldspink, 2012). Due the benefits promotes by physical activity, it is important to encourage elderly people to adopt regular physical practices (Boccia et al., 2015; McLeod et al., 2016) as a strategy to decrease the effects of senescence on muscle strength to maintain mobility safety and locomotion (Kent-Braun, 2009, Goldspink, 2012;). Within this scope, American College of Sports Medicine (ACSM) and American Heart Association (AHA) recommend a minimum of physical practice parameters for health of the elderly (Nelson et al., 2007). This parameters guide minimum weekly volume and intensity according to the mode of physical practice, and their combination, preserving the freedom of choice of the elderly according to convenience and personal profiles.

 

Source: Bing image generator (#Efdeportes)

 

    Physiological changes in the neuromuscular system generate losses in muscle mass, strength and function due to aging (Aoki, & Demura, 2011; Goldspink, 2012; Boccia et al., 2015), which make muscle strength a determining factor in the health of the elderly (McLeod et al., 2016; McGrath et al., 2020) of exercise’s intensity and volume rest interval, frequency of sessions types of exercise in physical and resistance training are capable of promoting significant effects on muscle strength and power (Aagaard et al., 2007; Chodzko-Zajko et al., 2009; Barbalho et al., 2017; Buch et al., 2017; Guizelini et al., 2018), and also to slow down changes in the muscle fatigue profile with aging. (Krüger et al., 2018)⁠

 

    The aging process promotes changes in the morphological characteristics of skeletal muscles. As a result, older adults are likely to develop sarcopenia and muscle atrophy that influence strength loss and fatigue, regardless of sports practice (Avin, & Frey Law, 2011). In other words, maintaining physical exercise by the subject does not eliminate the effects of aging on muscle strength performance.

 

    The handgrip strength is an important indicator of body strength (Schlüssel et al., 2008; Alonso et al., 2018) and has a positive relationship with the muscular strength of the lower limbs and dynamic postural balance of elderly women, and has a predictive character for giving up long-term exercise programs and for mortality (Gopinath et al., 2017; Alonso et al., 2018; Wiśniowska-Szurlej et al., 2019; McGrath et al., 2020). The handgrip strength of the elderly is a efficient resource for assessing physicals conditions of the elderly. Therefore, in this study we investigated the strength and strength fatigability and muscular activities of the forearm of elderly women during a handgrip task according to their physical level.

 

Material and methods 

 

    This research was submitted to and approved by a research ethics committee (Register CAAE: #61250116.30000.5505; Approval Reviewer: #3.975.467) and it was applied in accordance with the Declaration of Helsinki. Forty-one functionally healthy elderly people from the community of both sexes volunteered for this study free of charge and with documented consent. The inclusion criteria adopted were: female; no diagnosis of diabetes mellitus; and no osteoporosis or musculoskeletal injuries. Thirty-two volunteers were analyzed in the study, categorized into two groups based on physical activity. The group active was formed by 14 women (A group: 66.0 ± 6.3 years old; 70.6 ± 14.7 kg; 158.8 ± 6.1 cm; 27.8 ± 4.6 kg/m²) and the inactive was formed by 18 women (I group: 66.3 ± 5.1 years old; 67.5 ± 15.0 kg; 152.1 ± 4.8 cm; 29.2 ± 6.4 kg / m²). The ACSM/AHA (Nelson et al., 2007) recommendations for the regular practice of physical activity by the elderly were used as criteria for defining the groups.

 

Experimental procedure 

 

    The volunteers answered a questionnaire about their health history and their anthropometric measurements of body mass and height were obtained using a scale and a stadiometer.

 

    The handgrip strength assessment was performed on both hands (dominant and non-dominant hand) using a load cell (EMG Sytem, Brazil) with an accessory made for handgrip. The volunteers were asked to sit comfortably holding the load cell, the upper limbs hanging sideways to the body. After the familiarization attempt, the volunteers started the evaluation, which consists of two alternative and valid attempts for each hand. Through an oral command, each volunteer was instructed to perform explosive and maximum effort and maintain it isometrically until the end of the attempt, accompanied by vocal stimuli from the experimenter. Only the strongest attempt of each member was analyzed. (Avin, & Frey Law, 2011)

 

    A surface electromyograph with load cell synchronizer - EMG Sytem (1000 Hz, bandpass [20-500 Hz]) to assess forearm muscle activity (flexor carpi radialis and extensor carpi ulnaris) of volunteers during testing. The regions were prepared according to the recommendations of the Surface ElectroMyoGraphy for the Non-Invasive Assessment of Muscles and the same motor points used in Akesson and collaborators study (1997) were adopted.

 

Hand Grip and Muscle Activity Data Treatment 

 

    A custom algorithm was used to process and process the kinetic (force) and electromyographic (sEMG) data. Strength data were treated in two distinct phases: explosive phase - onset up to first force peak (Fpeak), and isometric phase - 15 seconds after Fpeak. The sEMG was filtered (Butterworth, 4th, bandpass: 20-500 Hz, and stopband: 60Hz) and normalized by the root mean square (RMS) of the surroundings of the sEMG at the time of Fmax (512ms).

 

    In the explosive phase, the following variables were extracted: rate of force development (RFD) - early (onset up to 200 ms); late (200 to 400ms); and peak. In the isometric phase, was extracted: the maximum isometric force (Fmax); average force of phase (Fmean); instantaneous force (Ftime) - every 2.5 seconds; rate of force loss (RFL) - was the instantaneous force divided by the peak; and static fatigue index (SFI) - was the difference between the actual area under the force curve and the hypothetical area under the curve (Severijns et al., 2015), in isometric phase.

 

    The EMGs were treated in signal amplitude (RMS) and frequency - mean frequency (MNF). The variables were extracted in the explosive phase (RMSe and MNFe) and isometric (RMSi and MNFi). In addition, instantaneous measurements were extracted from the 512 ms surrounding each Ftime.

 

Statistical analysis 

 

    Descriptive and inferential assessments were performed using Jeffrey’s Amazing Statistics Program (JASP; University of Amsterdam) software. Two-way Analysis of Variance (ANOVA) were performed on the dependent variables for the group (main effect) and handedness factors for the explosive phase variables and general variables of isometric phase. For the instantaneous variables, two-way ANOVA was performed with the inclusion of the third factor: instantaneous moment. The Holm Test was used for posterior analyses (Goss-Sampson, 2019). In cases of non-parametric data, the analyzes were replaced by the Friedman’s ANOVA followed by Connover’s post hoc or Mann-Whitney tests. Significance index p <0.05 was adopted, followed by substancial effect size determined by Cohen'd > 0.8.

 

Results 

 

    The time of uninterrupted practice of physical activity reported by the active group was: 3 women reported practicing from 6 months to one year; 2 for 1 to 2 years, another 2 for 2 to 5 years, and another 7 who have been practicing for more than 5 years. More specifically, 78.6% of women in the active group have been training for at least one year. Regarding the number of types of exercises practiced: 2 women reported only one type; others 8 reported 2 different types and 4 reported more than 2 types. The physical exercises most cited by this group were: Pilates method, water aerobics, functional training, strength exercises (muscular strength), walking, running/cooper, Yoga method or Lian Gong (Table 1). All mentioned at least 3 physical practice sessions per week, and in most cases, 5 sessions per week (7 women, 50% of the group).

 

Physical Capacity	Exercise Type / Method	Women (n)	%
Strength	Strength Training (dunbells, machines)	6	42.86%
	Pilates Method	9	64.29%
	Yoga Method or Lian Gong	2	14.29%
	Functional Training (bodyweight, resistance bands, plio box, bars)	6	42.86%
	Walking	3	21.43%
	Light Running	1	7.14%
	Water Aerobics	7	50.00%
Aerobic	Ciclyng	1	7.14%

Source: Own elaboration

 

    As for the level of physical activity, 9 elderly women in the active group were classified as physically active (69.2%) and 4 as physically very active (30.8%). In the inactive group, all volunteers were classified as insufficiently active. Results reinforced by the time of weekly physical practice significantly longer in the active group (17.27 ± 15.77h) compared to the inactive group (1.18 ± 1.42h; W(30.0): 2.0, p < 0.01).

 

    Active women were stronger than inactive in the explosive phase of handgrip strength, with the highest peak strength and highest rate of strength development. On the other hand, the inactive group presented more resistance than the active group for loss of strength during the isometric phase, obtaining a lower RLF and rate of fatigue in the non-dominant hand. Although, the strength of the active group was never lower than the inactive group (Table 2).

 

		Hand Dominant						Hand Non-Dominant
		A		I				A		I
		Mean	± SD	Mean	± SD	p		Mean	± SD	Mean	± SD	p
RFDpeak	[kg/s]	8.76	3.91	5.72	2.28	0.02	#	7.34	2.94	4.99	2.82	0.01	#
RFDearly	[kg/s]	15.39	12.73	12.60	12.43	0.44		17.85	10.68	8.70	9.92	0.01	#
RFDlate	[kg/s]	20.82	11.27	12.46	8.49	0.03	#	18.80	13.04	8.16	7.23	<0.01	#
Fmax	[kg]	17.86	5.77	15.23	4.34	0.12		15.82	5.12	11.94	2.49	0.02	*
Fmean	[kg]	15.66	5.92	13.13	3.61	0.28		13.31	4.68	10.46	2.35	0.12
Fpeak	[kg]	16.70	5.41	14.09	3.64	0.16		15.02	5.22	11.42	2.29	0.04	*
F 2.5s	[kg]	15.97	5.51	14.07	3.53	0.47		14.23	5.33	11.12	2.45	0.15
F 5.0s	[kg]	15.57	6.07	13.44	3.73	0.40		13.34	5.17	10.92	2.34	0.40
F 7.5s	[kg]	14.84	5.91	13.13	3.53	0.68		13.03	5.21	10.47	2.36	0.49
F 10.0s	[kg]	14.80	6.12	12.80	3.74	0.54		12.94	4.87	10.14	2.25	0.19
F 12.5s	[kg]	14.42	5.60	12.50	3.65	0.57		12.42	4.37	9.86	2.25	0.84
F 15.0s	[kg]	13.28	6.61	12.38	3.33	0.56		10.60	2.91	9.62	2.16	0.64
RFL 2.5s	[%]	6.26	5.87	1.85	7.38	0.23		8.43	7.92	4.76	7.52	0.19
RFL 5.0s	[%]	9.56	7.91	6.09	10.60	0.34		14.28	9.38	6.33	6.72	0.03	#
RFL 7.5s	[%]	13.59	8.24	8.13	10.34	0.13		16.58	9.17	10.32	7.42	0.049	*
RFL 10.0s	[%]	14.36	9.40	10.41	12.11	0.28		16.54	8.63	12.85	8.52	0.30
RFL 12.5s	[%]	15.94	7.00	12.49	12.74	0.34		19.17	9.78	15.12	9.54	0.40
RFL 15.0s	[%]	23.46	18.66	12.68	12.08	0.12		28.40	15.01	17.05	8.95	0.049	*
SFI	[%]	32.55	11.03	31.75	17.89	0.57		36.54	16.53	22.44	8.92	<0.01	#

A: Active Group; I: Inactive Group; SD: standard deviation; RFD: rate of force development;

 RFL: rate of force loss; SFI: static fatigue index; kg: kilogram; s: second. %: percentage. 

#: p<0.05 with large effect size. *: p<0,05 with medium effect size. Source: Own elaboration

 

    Extensor carpi muscle amplitude was significantly greater in active women compared to inactive women in the dominant hand (Table 3). However, in the non-dominant hand, the frequency of both muscles in the active group was significantly lower than in the inactive group in the isometric phase. In the flexor carpi muscle, this behavior was demonstrated along the phase, while in the extensor carpi muscles this result was found in the general frequency of the isometric phase, MNFi (Table 4). Then, the muscle activity pattern of the inactive group is characterized by less intermittence than the active group, which means that the inactive group request muscle fibers faster to accomplished the task compare to the pattern of request of active group.

 

Dominant Hand		Flexor Carpi				p	Extensor Carpi				p
		A		I			A		I
		Mean	± SD	Mean	± SD		Mean	± SD	Mean	± SD
RMS.e	[wu]	0.99	0.22	0.92	0.20	0.42	1.16	0.18	0.99	0.24	0.03	#
RMS.i	[wu]	1.21	0.17	1.24	0.44	0.20	1.19	0.18	1.25	0.25	0.52
RMSpeak	[wu]	1.18	0.16	1.13	0.22	0.70	1.24	0.20	1.12	0.18	0.17
RMS 2.5s	[wu]	1.18	0.19	1.22	0.16	0.80	1.18	0.24	1.19	0.18	0.65
RMS 5.0s	[wu]	1.26	0.27	1.24	0.18	0.91	1.16	0.25	1.15	0.23	0.47
RMS 7.5s	[wu]	1.08	0.21	1.24	0.29	0.29	1.12	0.31	1.17	0.36	0.74
RMS 10.0s	[wu]	1.20	0.28	1.21	0.38	0.95	1.22	0.29	1.14	0.46	0.30
RMS 12.5s	[wu]	1.17	0.27	1.23	0.46	0.70	1.14	0.35	1.17	0.63	0.47
RMS 15.0s	[wu]	1.10	0.38	1.24	0.45	0.68	1.02	0.26	1.32	0.95	0.65
MNF.e	[Hz]	93.23	13.31	100.07	13.16	0.23	100.86	12.44	95.59	14.68	0.36
MNF.i	[Hz]	86.00	13.29	88.16	13.71	0.72	91.53	16.71	97.28	13.46	0.33
MNFpeak	[Hz]	94.16	13.18	100.84	13.55	0.23	93.41	14.46	94.82	15.03	0.83
MNF 2.5s	[Hz]	93.21	16.30	100.63	15.22	0.18	91.03	13.23	92.16	12.97	0.86
MNF 5.0s	[Hz]	92.05	16.04	98.99	15.15	0.21	86.83	11.19	89.34	14.91	0.68
MNF 7.5s	[Hz]	92.37	17.28	97.72	15.63	0.34	87.40	13.30	87.99	15.17	0.93
MNF 10.0s	[Hz]	91.08	18.35	98.44	14.65	0.19	85.25	12.58	87.79	14.75	0.69
MNF 12.5s	[Hz]	90.29	18.21	96.47	11.94	0.50	85.49	15.79	87.51	13.07	0.75
MNF 15.0s	[Hz]	90.57	18.80	96.68	15.10	0.27	88.11	17.55	85.62	14.45	0.70

A: Active Group; I: Inactive Group; SD: standard deviation; e: explosive phase; i: isometric phase; 

RMS: root mean square; MNF: mean frequency; kg: kilogram; s: second. %: percentage. 

#: p<0.05 with large effect size. *: p< 0,05 with medium effect size. Source: Own elaboration

 

    Moment factor comparisons were significantly effective on muscle activity in active women. Comparisons between peak amplitude and instantaneous amplitudes indicated a significant reduction in the extensor carpi of the dominant hand (RMSpeak vs RMS7.5s, t: 2.838, p < 0.01; and vs RMS15.0s; t: 2.484, p = 0.02), and the frequency comparisons showed similarly decrease (MNFpeak vs MNF10.0s, t: 2.572, p = 0.01; vs MNF12.5s, t: 3.016, p < 0.01; vs MNF15.0s, t: 3.903, p < 0.01; Table 4). Therefore, there was a simultaneous decrease in the amplitude and frequency of muscle activity of the extensor carpi muscle of the active group, only in the dominant hand.

 

Non-dominant Hand		Flexor Carpi						Extensor Carpi
		A		I				A		I
		Mean	± SD	Mean	± SD	p		Mean	± SD	Mean	± SD	p
RMS.e	[wu]	1.01	0.22	0.98	0.23	0.71		1.09	0.18	1.01	0.17	0.34
RMS.i	[wu]	1.17	0.12	1.26	0.47	0.21		1.18	0.11	1.29	0.48	0.80
RMS.peak	[wu]	1.23	0.14	1.13	0.23	0.30		1.21	0.11	1.19	0.10	0.29
RMS 2.5s	[wu]	1.22	0.20	1.21	0.23	0.93		1.20	0.12	1.14	0.17	0.88
RMS 5.0s	[wu]	1.22	0.18	1.27	0.35	1.00		1.17	0.21	1.29	0.41	0.59
RMS 7.5s	[wu]	1.09	0.25	1.27	0.40	0.15		1.04	0.18	1.18	0.45	0.68
RMS 10.0s	[wu]	1.18	0.24	1.28	0.47	0.77		1.19	0.19	1.23	0.61	0.50
RMS 12.5s	[wu]	1.20	0.21	1.36	0.79	1.00		1.17	0.23	1.20	0.69	0.34
RMS 15.0s	[wu]	0.97	0.36	1.40	1.03	0.21		0.94	0.39	1.22	0.72	0.44
MNF.e	[Hz]	94.57	13.16	104.24	16.33	0.09		95.33	20.26	93.74	15.83	0.81
MNF.i	[Hz]	89.57	21.55	89.10	17.44	0.20		87.13	12.61	100.18	16.85	0.03	#
MNF.peak	[Hz]	88.64	13.16	99.71	13.38	0.02	#	92.22	21.92	91.28	17.21	0.65
MNF 2.5s	[Hz]	88.35	13.00	100.17	16.03	0.03	#	92.50	22.39	90.98	18.31	0.68
MNF 5.0s	[Hz]	88.54	15.25	99.66	12.61	0.04	*	89.72	22.02	89.57	18.10	0.56
MNF 7.5s	[Hz]	86.88	12.12	97.44	15.54	0.05		87.34	20.69	88.03	17.05	0.91
MNF 10.0s	[Hz]	86.02	13.22	98.23	14.44	0.03	#	85.61	21.49	87.48	17.85	0.59
MNF 12.5s	[Hz]	85.32	12.97	97.18	14.38	0.03	#	84.46	20.24	88.39	16.98	0.36
MNF 15.0s	[Hz]	87.16	13.58	98.08	13.64	0.05	*	82.39	20.76	86.69	17.72	0.51
MNF 12.5s	[Hz]	85.49	15.79	87.51	13.07	0.75		84.46	20.24	88.39	16.98	0.36
MNF 15.0s	[Hz]	88.11	17.55	85.62	14.45	0.70		82.39	20.76	86.69	17.72	0.51

A: Active Group; I: Inactive Group; SD: standard deviation; e: explosive phase; i: isometric phase; 

RMS: root mean square; MNF: mean frequency; kg: kilogram; s: second. %: percentage. 

#: p<0.05 with large effect size. *: p<0.05 with medium effect size. Source: own elaboration

 

    In the inactive group, comparisons of muscle activity throughout the isometric phase were also significantly effective. The frequency of extensor carpi muscle decreased gradually in the dominant hand, from 5 seconds until the end of the phase (MNFpeak vs MNF5.0s, t: 3.804, p <0.01; vs MNF7.5s, t: 4.735, p < 0.01; vs. MNF10.0s, t: 4.873, p£0.01; vs. MNF12.5s, t: 5.070, p < 0.01; vs. MNF15.0s, t: 6.377, p < 0.01, Table 3). In the non-dominant hand, the frequency was lower in the last moment of the phase (MNFpeak vs MNF15.0s; t: 3.346, p = 0.03; Table 4). The decrease in muscle activity frequency associated with the increase in the amplitude characterizes muscle fatigue(Powell et al., 2007), hence, the inactive group seems more susceptible to fatigue along the handgrip strength compared to the active ones.

 

Discussion 

 

    The handgrip strength and fatigue and forearm muscle of elderly women were evaluated in this study to verify the effects of the physical activity of them. The profile of physical activities performed by the active group is mostly muscle strength with a minimum of 3 training sessions per week. As main results, active women were stronger and more explosive than inactive women in non-dominant handgrip strength. And the flexor carpi muscle of the non-dominant hand has a different activation pattern between groups, active women request less than inactive women.

 

    The muscular strength of the elderly is responsive to several strength / resistive training modes: traditional, functional, circuit, low or high volume (Aagaard et al., 2007; Buch et al., 2017; Aragão-Santos et al., 2019). The active group of this study was characterized by the high presence of strength exercises, which favored the palm grip strength of this elderly person. Strength training that includes upper-limb exercises effectively improves maximal handgrip strength in older adults, especially when manual grip is included in training. (Labott et al., 2019)

 

    Active group have different strategy of muscle activation compare to inactive women was another result of the present study. This founding indicates that the women physically active request different muscle fibers to accomplish the handgrip strength than inactive elderly women. However, comparisons of muscle fiber between older adults with no athletic history and older adults who have won medals in world events or world records in athletics revealed that exclusively aerobic physical practices performed by the elderly are insufficient to change the morphophysiological adaptations already inherent to aging, not having identified differences in the profiles of muscle fibers (Power et al., 2016). This reinforces that specificity of training directly influences muscle morphological adaptations.

 

    In this reasoning, especially in terms of rapid strength, strength training has the ability to improve the efficiency of muscle fiber performance in the elderly (Wang et al., 2017), being a useful tool for the development of muscle strength in these people. Mainly because the elderly show substantial gains in muscle strength due to strength training, explosive or traditional (Guizelini et al., 2018). Add to this, the explosive training being more effective in gaining strength development rate (Guizelini et al., 2018). Thus, the physically active pattern of these women were sufficient to promote changes in their muscle contraction strategies, reflecting rapid gains in strength.

 

    In a randomized controlled clinical trial, adults (40 to 65 years old) were grouped into three parallel physical training methodologies: (i) combined training (resistance training, functional training or training consisting of regular physical practices) as recommended by the World Health Organization; (ii) high-intensity interval training, 2 sessions per week; and (iii) a high intensity interval training adding whole body electromyostimulation group. After 12 weeks, the combination training and high-intensity interval training groups achieved negligible gains in handgrip strength (Amaro-Gahete et al., 2019). In another controlled clinical trial with 48 postmenopausal elderly women, grouped into two functional training groups: (i) applied in a single-set and (ii) applied in multiple-set, found insufficient and inconsistent gains in muscle power in the upper limbs after 72 training sessions, carried out in 24 weeks, regardless of the method applied. Although these trainings have promoted positive results in the lower limbs of the participants. The authors attributed such results to the content proposed in the training, which planned each training session with a maximum of 30% of exercises for the upper limbs, which favored the concentration of exercises in other body segments, such as the lower limbs. (Rocha et al., 2023)

 

    Similarly, in a parallel randomized controlled trial, there was no success in handgrip strength gains in both hands of men and women with multiple sclerosis after 16 sessions of Tai-Geiko (oriental physical practice), two sessions weekly; although, this training has provided effective results in dynamic balance and functional tests of the participants (Ultramari et al., 2020), due to the low concentration of exercises for upper limbs applied in the training of the study. Thus, in order to improve handgrip muscle function, it is necessary to carry out physical practices with a relevant volume (session frequency and practice time) of exercises aimed at developing the upper limbs.

 

    In addition, physically active women also perform better on muscle fatigue compared to inactive women. The non-dominant hand grip strength of the inactive group in this study showed no loss of muscle strength while the active group did. This indicates that there is an effect of physical practice on the loss of strength in elderly women.

 

    Controversially, aging muscle fatigue due to sarcopenia and muscle atrophy is associated with other morphophysiological adaptations characteristic of musculature (Avin, & Frey Law, 2011). Consequently, these underlying mechanisms provide the elderly with greater resistance to fatigue, regardless of the level of physical activity and type of muscle contraction (Avin & Frey Law, 2011). Although sarcopenia and atrophy were not investigated in this study, our findings suggest that physical activity influenced the loss of handgrip muscle strength in elderly women, especially in the non-dominant hand.

 

    During handgrip strength, the muscle activity of the active women decreased - amplitude and frequency, while in the inactive group only the muscle frequency decreased. Peripheral muscle fatigue is verified with a gradual reduction in the frequency of muscle activity throughout the task associated with an increase in the amplitude of muscle activity (Merletti, & Lo Conte, 1997; Boccia et al., 2015; Shair et al., 2017). Considering that active women were stronger and the muscle activity profile of both groups was different, the results of this study suggest that inactive women are more susceptible to peripheral fatigue in handgrip strength compared to active women.

 

    There are several factors that contribute to the reduction of adherence of the elderly to physical training, consequently, this inhibits gains in physical health. Thus, this may explain the small sample regarding the inclusion criteria of the study. However, the present study is in line with other studies on fatigue in physically active older adults (or the effects of physical training in older adults) based on low and heterogeneous sampling (Avin, & Frey Law, 2011). Because of this, strong effects analyzes were included in the inferential analyzes of this study, in order to minimize errors in the interpretation of results..

 

    However, based on these results and due to the importance of manual skills for the daily activities of the elderly, the inclusion of handgrip strength exercises in physical therapy and physical exercises with adequate training volume should reduce the effects of aging on handgrip strength and contribute to muscle function in elderly women. For example, according to the results of the present study, they indicate that active elderly women are better able to handle heavier objects and reach handrails/grab bars with greater safety. Furthermore, these results confirm the consensus that a physically active lifestyle according to the ACSM/AHA (Nelson et al., 2007) recommendations is beneficial for the elderly.

 

Conclusion 

 

    The active elderly women presented better performance of strength, fatigability and muscle activity in handgrip strength in relation to the inactive ones. This result was attributed to the volume of strength training or strength training combined with another type of training by older women for at least six months. Furthermore, improving manual strength can contribute to the performance of activities of daily living and, consequently, to the quality of life of active elderly women.

 

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Lecturas: Educación Física y Deportes, Vol. 28, Núm. 306, Nov. (2023)