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In this study the effects of infrared lamp illumination during the muscle fatigue process was studied. Three different groups (n=5) were used: one control group and two treated ( Infrared Lamp 780- 1400nm), with the energy densities of 0.5 and 1.0 J/cm 2 and time of illumination of 300 seconds. The treated animals were illuminated in one point directly in the tibiali s muscle, after the first tetanic contraction out of six, with an interval between each tetany. The results were registered in an electrophysiograph and the intensity of the force of contraction in grams w as analysed. It was observed that the control group presented a reduction in the intensity of the force of contraction, while the treated group managed to maintain it, which was clearly evident in the energy density of 0.5 J/cm 2. It was concluded that the use of the infrared lamp illumination was efficient c oncerning resistance to muscle fatigue.
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Brazilian Archives of Biology and Technology
Vol.50, n. 3 : pp.403-407 May 2007
ISSN 1516-8913 Printed in Brazil BRAZILIAN ARCHIVES OF
Effects of the Infrared Lamp Illumination during the
Process of Muscle Fatigue in Rats
Andréia Zarzour Abou-Hala1, Daniella Galvão Barbosa2, Rodrigo Labat Marcos3, Cristina
Pacheco-Soares1 and Newton Soares da Silva1*
1Laboratório de Biologia Celular e Tecidual; 2Laboratório de Fluorescência; 3Laboratório de Fisiologia e
Farmacodinâmica; Instituto de Pesquisa e Desenvolvimento; Universidade do Vale do Paraíba - UNIVAP; Av.
Shishima Hifumi, 2911;; 12244-000; São José dos Campos - SP - Brasil
In this study the effects of infrared lamp illumination during the muscle fatigue process was studied.
Three different groups (n=5) were used: one control group and two treated (Infrared Lamp 780-
1400nm), with the energy densities of 0.5 and 1.0 J/cm2 and time of illumination of 300 seconds. The
treated animals were illuminated in one point directly in the tibialis muscle, after the first tetanic
contraction out of six, with an interval between each tetany. The results were registered in an
electrophysiograph and the intensity of the force of contraction in grams was analysed. It was observed
that the control group presented a reduction in the intensity of the force of contraction, while the treated
group managed to maintain it, which was clearly evident in the energy density of 0.5 J/cm2. It was
concluded that the use of the infrared lamp illumination was efficient concerning resistance to muscle
Key words: Muscle fatigue; infrared illumination; muscle tension; tetany
* author for correspondence
Muscle fatigue can be defined as the group of
manifestations produced by work or prolonged
exercise. The consequence will be the reduction in
maintaining or continuing the expected result
(Rossi, 1999; Schwid, 2002). Muscle fatigue may
alter muscle functioning due to the exhaustion of
mediators at several levels, which can establish a
muscular unbalance, making easier the appearance
of lesions (Fitts, 1996). Possible causes of the
muscle fatigue can be failure of the motor nerve,
the neuromuscular junction, the central nervous
system and also the contractile mechanism, in
which fatigue takes place due to the depletion of
the adenosine triphosphate and muscular glycogen
stock and the large amount of lactic acid (Fox et
al., 1991; Thomas et al., 2003). Muscle fatigue
may be the result of impairments at any of a
number of sites within the neuromuscular system,
which manifests as a decline in the maximum
force-generating capacity of the muscle (Fulco
at al., 2001; Allman and Rice, 2002).
The skeletal muscle, when exposed to intense and
continuous effort, tends to lose its contractile
capacity. This occurs because during the
contraction, the intramuscular pressure exceeds the
blood pressure, obliterating small nutrition vessels
and the oxygen flow as well. The muscle cells
obtain energy through the anaerobic glycolysis in
Abou-Hala, A. Z. et al.
Brazilian Archives of Biology and Technology
which the metabolic result is the lactic acid.
Clinically, this phenomenon is interpreted as
contractures and reduction of the muscular
functional capacity, due to decrease in the peak
tension and power (Fitts, 1996).
The use of infrared (IR) radiation in the treatment
of a variety of medical conditions has been studied
for a long time. The IR radiation is applied in the
inner part of the electromagnetic spectrum which
generates heat when absorbed by matter (Kitchen
and Partridge, 1991; Gul and O'Sullivan, 2005).
According to Moss et al. (1989), many sources
which emit either visible or ultraviolet radiation
will also emit IR and this IR radiation have
different refractive indices and different reflection,
transmission and scattering characteristics,
depending on the wavelength of the light. Infrared
radiation in the IR-B (medium infrared: 1.4 - 3µm)
and IR-C (long infrared: 3µm - 1mm) ranges is
absorbed in the top layers of the skin. The shorter-
wavelength IR-A radiation (780 - 1400ηm) has a
greater penetrating power. The IR lamp, a non-
coherent irradiation, has a wavelength spectrum
with a pronounced peak approximately 1000ηm in
the deep-penetrating IR-A range. All of these
patterns are quite important when measuring IR
radiations but only the reflection and absorption
are extremely meaningful biologically and
clinically since they have been considered effects
of IR radiation on tissues.
The investigation into the effect of the IR lamp
illumination during the process of muscle fatigue
in tibialis anterior muscle of rats was the main goal
of this study.
In this study the ethical principles of animal
experimentation was applied in conformity to
COBEA (Brazilian School of Experimentation
Animal), having been approved by the Committee
of Ethics in Research of UniVap, Protocol
L007/2003/CEP. Fifteen (15) male Wistar rats
were used, weighing between 250 and 300g.
During the experiment, the animals were housed
under standard conditions in cages, five animals
per cage and kept under constant conditions of
temperature (22±2°C) with a 12-h light/12-h dark
cycle. The rats were fed with ad libitum and
supplied with drinking water.
All surgical procedures were performed under
aseptic conditions. Each animal was pre-
anesthetized with Butorfanol (Torbugesic), in
the dose of 2 mg/Kg via intramuscular (Flecknell,
1996). After 15 minutes, the rat was sedated with
chloral hydrate (i.p.), in the dose of 420mg/kg in a
10% solution (Almaguer-Melián et al., 1999) and
placed on a surgical table where it was carried
through the withdrawal of the skin and dissecation
of the muscle previous tibial with the purpose to
isolate the nerve fibular deep (responsible for the
stimulation of the muscle) isolated the nerve, in
the region of the insertion next to the plantar to
metatarsus region, the muscle (through the tendon)
was connected to an isometric transducer (Ugo
Basile®; Vareze, Italy) that it transforms the data
of muscle tension into electric signals transmitted
to the electrophysiograph and the nerve connected
to a bipolar electrode, on to the eletrostimulator,
for indirect inervation of the muscle.
The muscle was exposed to a constant tension of
10g. The muscle was stimulated indirectly by
pulses of 7 V, 0.2Hz for 2 miliseconds. The
muscle and tetanics contractions in response to the
indirect stimulations were registered in a
physiograph (GEMINI 7070 of UGO BASILE®)
through the isometric transducer for approximately
60 minutes. To stimulate the tetanic contraction,
the frequency was raised to 60 Hz, every 10
minutes, out of six contractions (Marcos, 2002;
Lopes-Martins et al., 2006). During the whole
experiment, the muscle was dampened with a
sterile saline solution (0.9%) to prevent drying.
The muscle fatigue was determined by the
incapacity to keep the muscle contraction.
Therefore, there would be a decline of the
amplitude in 50% maximum contraction muscle
recorded, to prevent the death of the tissue because
of the tetanic contraction.
The animals were divided in three groups, which
1) Control group: not radiated, with stimulation of
6 tetanic contractions;
2) Infrared Lamp Illumination, energy density of
3) Infrared Lamp Illumination, energy density of
A PHILIPS® lamp - Infrared 780-1400nm (Fig. 1)
was used. The treated animals were illuminated in
one point after the stimulation of the first tetanic
contraction, directly in the tibialis muscle exposed
at that moment. The patterns of each protocol are
indicated in table 1.
At the end of each experiment the animals were
killed with excessive intracardiac dose of Sodium
Effects of the Infrared Lamp Illumination during the Process of Muscle Fatigue in Rats
Brazilian Archives of Biology and Technology
Thiopental (Thiopentax®), 60mg/kg (Thurmon,
1999). The data obtained were analyzed
statistically by the test of variance analysis to 5%
of probability (ANOVA). The average and the
standard error (s.e.) of the average was calculated
and the difference among the data of the control
group and irradiated was determined by the Tukey
test. Significant values were considered
statistically with p< 0.05, p<0.01 and p<0.001.
Figure 1 - Esquematic drawing of the assembly of the box: (1) Infrared Lamp (Philips®), (2)
Wooden Pinhole (Ø 5mm), (3) Lens (CSR® - Ø 50mm 6x) and (4) Filters
Table 1 - Protocol of IR irradiation
Parameters of irradiation Values Values
Energy density 0.5 J/cm2 1 J/cm2
Potency 0.5 mW 1 mW
Wavelength 780-1400 nm 780-1400 nm
Area 0.3 cm2 0.3 cm2
Time 300 seconds 300 seconds
The results of the intensity of the force of
contraction measured in each electric stimulation,
after tetany were analyzed (Fig. 2). It was
observed that in the control group a decrease in the
muscle tension (intensity of the muscle force)
occurred during the tetanic contractions and this
reduction was even better observed by a fall after
the first tetanic contraction.
In the treated group with energy density of
0.5J/cm2, a significant fall was not observed. In the
treated group with energy density of 1.0J/cm2, a
significant fall was observed after the third tetanic
contraction, being more highlighted from the
fourth contraction on.
In the animals of the control group, the most
significant fall of 26.7% was observed. The treated
group with 0.5J/cm2 presented a fall of 6.0%
(lesser fall) and the treated group of 1.0 J/cm2
presented a fall of 14.5%.
Abou-Hala, A. Z. et al.
Brazilian Archives of Biology and Technology
** Control
Muscular tension during tetanic contraction (g)
Number of tetanic contraction
Group 1 2 3 4 5 6
Control 18.4 17.1±0.1278 16.3±0.2556 15.5±0.1826 14.5±0.3034 13.2±0.1258
0.5J/cm2 18.4 18.8±0.3452 18.0±0.2154 17.4±0.4169 17.0±0.3262 16.9±0.2880
1.0J/cm2 18.4 18.1±0.3475 17.4±0.2909 16.8±0.2733 15.9±0.4264 15.4±0.4992
Figure 2 - Intensity of the muscle contraction force by tetanic contractions (mean± se) (* p< 0.05,
** p<0.01 and *** p<0.001)
This study has investigated, through the IR lamp
illumination, the reduction of the muscle fatigue in
tibialis anterior muscle of rats after stimulation of
tetanic contractions by indirect electrical stimulus.
By using the IR lamp illumination with energy
densities of 0.5 and 1.0 J/cm2, it was possible to
observe a reduction in the intensity of the force of
contraction of 6.0 and 14.5%, respectively; both
being less than the control group (26.7%). High
levels of certain metabolites in the blood, due to
the increased metabolic activity arising from the
high temperatures, have a direct effect on vessel
walls, stimulating vasodilation (Ward, 1986; Wells
et al., 1988; Ganong, 1989). According to
Massuda et al. (2005), the high rate of metabolism
due to increased body temperature and increased
blood flow, decreased subjective symptoms,
resulting in increased energy scores, hence
promoting a better resistance related to muscular
Although has been proved that the use of the IR
lamp illumination improve the resistance, further
studies should be done in order to determine such
effects, clearly showing that the treatment with the
IR lamp illumination was efficient.
It could be concluded that the use of the IR lamp
illumination with energy density of 0.5 J/cm2
promoted more resistance to the muscle fatigue.
We are grateful to Chaker Nayef Abou Hala and
Ana Paula Marques de Mendonça Lopes for
technical assistance, and Renato Amaro Zângaro,
PhD (Laboratório de Fluorescência).
Neste estudo investigamos o efeito da irradiação
da lâmpada infravermelha durante o processo de
fadiga muscular. Foram utilizados 3 grupos
diferentes (n=5), sendo 1 grupo controle e 2
irradiados (Lâmpada de Infravermelho 780-
1400nm), nas densidades de energia 0,5 e 1,0J/cm2
e tempo de irradiação 300 segundos. Os animais
irradiados receberam 1 irradiação em 1 ponto,
diretamente no músculo tibial, após a primeira
contração tetânica de um total de seis, com um
intervalo entre cada tetania. Os resultados foram
registrados em eletrofisiógrafo e analisado a
intensidade da força de contração em gramas. Foi
observado que o grupo controle apresentou uma
Effects of the Infrared Lamp Illumination during the Process of Muscle Fatigue in Rats
Brazilian Archives of Biology and Technology
redução na intensidade da força de contração, já os
grupos irradiados conseguiram mantê-la, sendo
mais evidente quando irradiado com densidade de
energia (DE) de 0,5J/cm2. Conclui-se que a
utilização da irradiação da lâmpada infravermelha
é eficaz na resistência a fadiga muscular.
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... Segundo os autores o emprego de doses da ordem de 1 a 3 J pode promover a redução dos níveis de lactato sanguíneo pós-exercício intenso associado à fototerapia com laser no IV. A fadiga muscular pode ser definida como uma manifestação produzida por exercício prolongado (Dimitrova e Dimitrov, 2003), alterando a atividade muscular devido ao esgotamento de mediadores químicos (Abou-Hala et al., 2007). Os resultados não significativos do tempo de fadiga, observados no presente estudo, contrariam os dados apresentados por Almeida et al. (2012), De Marchi et al. (2012) e Leal Junior et al. (2009a, 2009b e, os quais Tabela 2. Valores de RMS, força, tempo de fadiga e níveis de lactato sanguíneo pré (controle) e pós-terapia (placebo, laser ou LED). ...
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INTRODUÇÃO: Estudos têm demonstrado a efetividade do laser no infravermelho (IV) sobre a atividade musculoesquelética. Contudo, não foram observados estudos sobre os efeitos da radiação emitida por um LED (Light Emitting Diode) no IV sobre a atividade do músculo masseter (MM, importante músculo da mastigação), sendo este o objetivo do presente estudo. MÉTODOS: Participaram do estudo 10 voluntários, os quais foram analisados por eletromiografia (atividade muscular, força e tempo de fadiga) e nível de lactato sanguíneo (mmol/L) após terapia placebo, laser (GaAlAs, 780 nm) e LED (GaAlAs, 880 nm). Os sinais obtidos previamente antes de realizadas as terapias foram tidos como controle. Os parâmetros de irradiação (laser ou LED) foram: potência de saída de 0,02 W, densidade de energia de 4 J/cm2, área do feixe de 0,2 cm2. Foram irradiados 8 pontos sobre o MM, de forma perpendicular e transcutânea, com distância de 1 cm entre os pontos. RESULTADOS: A atividade muscular foi significativamente maior pós-terapia laser e LED em relação aos valores controle. Não foram encontradas diferenças significativas nos valores de força, tempos de fadiga e níveis de lactato sanguíneo pós-terapia placebo, laser ou LED, quando comparados aos valores controle. CONCLUSÃO: Os resultados obtidos no presente estudo sugerem a otimização da atividade muscular com uso de terapia laser ou LED, sem causar efeitos colaterais, como a elevação de força e aumento dos níveis de lactato.
We examined the changes in skin conditions before and after the application of electroluminescent infrared heating lamp to the body regions of healthy Korean men. We assessed the differences in sebum, moisture, pores, wrinkles, pigmentation, and elasticity of the skin in the forearm, back, and shin regions. A total of 30 healthy men in their 20s were enrolled. We used a Skin Diagnosis Meter for skin state measurements. Statistical differences were found between the pre- and post-measurement values in the moisture, wrinkles, pigmentation, and elasticity of skin. In the correlation analysis results, moisture and wrinkle, moisture and elasticity, pore and pigmentation, and wrinkle and elasticity were positively correlated, respectively. However, moisture and pore, moisture and pigmentation, pore and wrinkle, pore and elasticity, wrinkle and pigmentation, and pigmentation and elasticity were negatively correlated, respectively. These results suggest that the change in skin condition is associated with external stimulants. The effect of infrared radiation on the various skin conditions may differ depending on the part of the body.
Objective: To evaluate the effects of infrared-light-emitting diode (LED) during treadmill training on functional performance. Methods: Thirty postmenopausal women aged 50-60 years were randomly assigned to one of three groups and successfully completed the full study. The three groups were: (1) the LED group, which performed treadmill training associated with phototherapy (n = 10); (2) the exercise group, which carried out treadmill training only (n = 10); and (3) the sedentary group, which neither performed physical training nor underwent phototherapy (n = 10). Training was performed over a period of 6 months, twice a week for 45 min per session at 85-90% of maximal heart rate, which was obtained during progressive exercise testing. The irradiation parameters were 100 mW, 39 mW/cm(2) and 108 J/cm(2) for 45 min. Quadriceps performance was measured during isokinetic exercise testing at 60°/s and 300°/s. Results: Peak torque did not differ amongst the groups. However, the results showed significantly higher values of power and total work for the LED group (∆ = 21 ± 6 W and ∆ = 634 ± 156 J, p < 0.05) when compared to both the exercise group (∆ = 13 ± 10 W and = 410 ± 270 J) and the sedentary group (∆ = 10 ± 9 W and ∆ = 357 ± 327 J). Fatigue was also significantly lower in the LED group (∆ = -7 ± 4%, p < 0.05) compared to both the exercise group (∆ = 3 ± 8%) and the sedentary group (∆ = -2 ± 6%). Conclusions: Infrared-LED during treadmill training may improve quadriceps power and reduce peripheral fatigue in postmenopausal women.
This study aimed to explore if the red light irradiation can affect the electrophysiology performance of flexor digitorum superficialis (FDS) and fatigue recovery. Four healthy volunteers were randomly divided into two groups. In the designed force-tracking tasks, all subjects performed the four fingertip isometric force production except thumb with a load of 30% of the maximum voluntary contraction (MVC) force until exhaustion. Subsequently, for the red light group, red light irradiation (640 nm wavelength, 0.23J/cm2, 20 min) was used on the right forearm; for the control group, the subjects relaxed without red light irradiation. Then subjects were required to perform fatigue trail again, and sEMG signal was collected simultaneously from FDS during finger force production. Average rectified value (ARV) and median frequency (MF) of sEMG were calculated. Compared to the control group, the red light irradiation induced more smoother value of ARV between 30% and 40%, and the value of MF was obviously large and smooth. The above electrophysiological markers indicated that recovery from muscle fatigue may be positively affected by the red light irradiation, suggesting that sEMG would become a power tool for exploring the effect of red light irradiation on local muscle fatigue.
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Introdução: O objetivo deste estudo foi avaliar a força contrátil, a resistência à fadiga e a integridade fibrilar de um músculo fundamentalmente constituído de fibras anaeróbicas (tibial anterior) de ratos submetidos a treinamento aeróbico com natação. Materiais e Métodos: 21 ratos machos Wistar (353±32g) foram divididos em três grupos experimentais (n=7): grupo controle (GC), grupo treinado com carga (5% da massa corporal) em meio líquido (GTC) e grupo treinado sem carga em meio líquido (GT). O protocolo de treinamento de natação teve 1h diária, por cinco dias consecutivos, durante cinco semanas. Após 72h do período experimental, obteve-se o registro eletrofisiográfico do músculo tibial anterior: a) tensão máxima gerada pelo músculo (g); b) tempo (s) que o músculo manteve-se contraído até 50% da tensão máxima; e c) a área sob a curva tetânica (cm2) até 50% da tensão máxima, durante cada contração tetânica induzida. Além disso, foi feita análise histológica desse músculo. Para análise dos dados foi aplicado ANOVA, seguida pelo teste Tukey-Kramer. Resultados: Os resultados demonstraram que o GT apresentou valores significativamente superiores (p<0,05) em relação os demais grupos para a variável tempo de contração a 50% da tensão máxima. Além disso, a análise histológica não evidenciou qualquer tipo de dano muscular. Discussão: concluiu-se que o protocolo de treinamento utilizado sem o implemento de peso promove melhores adaptações musculares, aumentando a capacidade do músculo tibial anterior em resistir à fadiga.
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A fadiga, ou incapacidade de manter o rendimento durante exercício físico moderado e prolongado, tem sido tradicionalmente atribuída à inibições nos mecanismos de contração do músculo esquelético: a denominada fadiga periférica. Diversos trabalhos, recentemente, têm apontado que a fadiga durante o exercício de resistência pode ser atribuída à atividades serotonérgicas cerebrais (fadiga central), bem como ao o papel de certos aminoácidos, principalmente os de cadeia ramificada e os aromáticos, cujos substratos para o metabolismo intermediário são precursores de neurotransmissores do cérebro. Há agora convincentes evidências de que a indução pelo exercício nas alterações da razão triptofano livre (TrpL)/aminoácidos neutros (AAN) está associada com aumento da concentração de serotonina cerebral e desenvolvimento de fadiga. A influência da manipulação nutricional na proporção TrpL/AAN no desempenho é ainda menos conhecida. O objetivo desta revisão é avaliar os prováveis mecanismos da fadiga central e periférica e as prováveis relações entre elas.
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Lesion of the fimbria-fornix causes dysfunction of learning processes and has been used in animal models for the study of Alzheimer's disease. With the objective of comparing the efficacy of two methods of producing a lesion of the fimbria-fornix, 40 young male Sprague-Dawley rats were distributed in four experimental groups: control (6), falsely lesioned (8), lesion due to aspiration (12) and lesion due to transection (14). The results showed that whilst with both techniques, in rats, serious cognitive defects were produced, as expressed by the high latencies of escape and small number of crossings of Morris's aquatic labyrinth, the aspiration lesion led to greater mortality than the transection lesion did. Similarly, the aspiration technique in rats induced hyperactivity, aggressiveness and tigmotaxia, while in the rats with lesions due to transection tigmotaxia ceased after their first attempts and hyperactivity on the second day of training. These results would suggest that a bilateral lesion due to transection of the fimbria-fornix is an effective alternative to an aspiration lesion to interrupt this pathway.
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Recently, we reported that, at similar voluntary force development during static submaximal intermittent contractions of the adductor pollicis muscle, fatigue developed more slowly in women than in men under conditions of normobaric normoxia (NN) (Acta Physiol Scand 167: 233-239, 1999). We postulated that the slower fatigue of women was due, in part, to a greater capacity for muscle oxidative phosphorylation. The present study examined whether a gender difference in adductor pollicis muscle performance also exists during acute exposure to hypobaric hypoxia (HH; 4,300-m altitude). Healthy young men (n = 12) and women (n = 21) performed repeated static contractions at 50% of maximal voluntary contraction (MVC) force of rested muscle for 5 s followed by 5 s of rest until exhaustion. MVC force was measured before and at the end of each minute of exercise and at exhaustion. Exhaustion was defined as an MVC force decline to 50% of that of rested muscle. For each gender, MVC force of rested muscle in HH was not significantly different from that in NN. MVC force tended to decline at a faster rate in HH than in NN for men but not for women. In both environments, MVC force declined faster (P < 0.01) for men than for women. For men, endurance time to exhaustion was shorter (P < 0.01) in HH than in NN [6.08 +/- 0.7 vs. 8.00 +/- 0.7 (SE) min]. However, for women, endurance time to exhaustion was similar (not significant) in HH (12.86 +/- 1.2 min) and NN (13.95 +/- 1.0 min). In both environments, endurance time to exhaustion was longer for women than for men (P < 0.01). Gender differences in the impact of HH on adductor pollicis muscle endurance persisted in a smaller number of men and women matched (n = 4 pairs) for MVC force of rested muscle and thus on submaximal absolute force and, by inference, ATP demand in both environments. In contrast to gender differences in the impact of HH on small-muscle (adductor pollicis) exercise performance, peak O(2) uptake during large-muscle exercise was lower in HH than in NN by a similar (P > 0.05) percentage for men and women (-27.6 +/- 2 and -25.1 +/- 2%, respectively). Our findings are consistent with the postulate of a higher adductor pollicis muscle oxidative capacity in women than in men and imply that isolated performance of muscle with a higher oxidative capacity may be less impaired when the muscle is exposed to HH.
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Fatigue is a very common symptom of multiple sclerosis (MS). Theoretically, fatigue may be related to neuromodulation by soluble products of the autoimmune process or by disruption of central nervous system pathways necessary for sustained activity, but little empirical evidence supports these possibilities. Amantadine, pemoline, and modafanil improved fatigue in placebo-controlled clinical trials, but these studies all had significant limitations. Difficulty measuring fatigue has impeded studies of its characteristics, mechanisms, and therapeutics. Most studies have relied on self-report questionnaires. These may be inappropriate, however, because they can be easily confounded by other symptoms of MS, they are entirely subjective, and they require patients to make difficult retrospective assessments. Studies of fatigue would be improved by including measures of more rigorously defined, quantifiable components of fatigue. For example, motor fatigue can be measured as the decline in strength during sustained muscle contractions. Cognitive fatigue can be measured as the analogous decline in cognitive performance during tasks requiring sustained attention. Lassitude is defined as a subjective sense of reduced energy, and it can be measured with the use of a visual analog diary. These measures provide reproducible results and demonstrate significant differences between MS patients and healthy controls. Dividing fatigue into these components can provide objective assessments that are less likely to be confounded by other symptoms of MS, such as weakness, spasticity, cognitive impairment, and depressed mood.
Infra-red therapy has been used in clinical practice for a considerable period of time; there are, however, a limited number of studies which evaluate the efficacy of this modality in the management of clinical conditions. This review considers the physical behaviour, physiological effects, the efficacy and hazards of infra-red therapy.
High-intensity contractile activity causes a rapid fall in peak tension or force, a reduced shortening velocity, decline in power, prolonged twitch duration, a sarcolemma action potential with a prolonged duration, reduced amplitude, and a conduction velocity that may result in conduction block. The calcium transient is characterized by a reduced amplitude and prolonged duration. What is the role of hydrogen in high-intensity exercise? It may affect E-C coupling but we do not think so. It definitely inhibits the rate of force development and calcium binding to TN-C. It also definitely inhibits the cross-bridge transition from the low to high force state. It inhibits velocity or the cross-bridge cycle rate and, therefore, decreases power and, importantly, prolongs the rate of calcium reuptake by inhibiting the sarcoplasmic reticulum calcium ATPase pump. Phosphate inhibits tension by reversing the cross-bridge transition from the low to the high force state, but it does not affect cycle rate; therefore, it does not have an effect on velocity. It may be involved in decreasing the free energy of ATP hydrolysis, which would provide less energy and, most importantly, play a role in inhibiting the sarcoplasmic reticulum calcium reuptake. Finally, what does all this mean to the athlete and how can fatigue be prevented? Basically, we do not have answers to these questions, but it is clear that the athlete is going to have to have a varied training program. If an athlete trains with one particular type of exercise, fatigue will result from other factors. Thus, a heterogeneous training program is essential. Diet is very important, and warm-up and fluid replacement are all factors that are going to be important in triggering peak performance.
A limited number of studies have investigated the effect of old age on neuromuscular fatigue, yet a variety of protocols have been used to compare the fatigability of old and young humans. These include voluntary isometric and isokinetic contraction protocols at maximal and submaximal intensities, and electrical stimulation protocols of continuous or intermittent stimulation at a variety of stimulation frequencies. The results of these studies are summarized in this review. Although it seems reasonable to suggest that age-related changes in muscle morphology and motor unit remodeling, as well as the associated loss of strength and slowed contractile properties, may improve the resistance to neuromuscular fatigue in old humans, the collective results suggest that it is not possible to make this generalization. In fact, it cannot be generalized that the muscles of old humans are either more or less fatigable than young adults because the extent of the difference in fatigability relies strongly on the fatigue task performed (task-dependency). Age-related changes that occur within the neuromuscular system may result in some candidate fatigue sites increasing or decreasing their susceptibility to failure under specific task conditions. These candidate fatigue sites include central drive, muscle membrane excitability, excitation-contraction coupling mechanisms, and metabolic capacities. The effect of old age on these various central and peripheral sites is discussed with respect to their relative contribution during different fatigue tasks. Moreover, the impact of the possible confounding effects of subject habituation, physical activity status, and sex on the fatigability comparison is addressed.