Absence of gender differences in the fatigability of the forearm muscles during intermittent isometric handgrip exercise.Abstract
Previous studies have reported women to have a greater resistance to fatigue than men during sustained handgrip exercise, however, observed gender differences in fatigue has been shown to be a function of contraction type. The purpose of the present study was to determine if gender differences exist in forearm muscle fatigue during intermittent handgrip contractions. Women [n = 11, 23.5 [+ or -] 1.5 (SE) yr] and men (n = 11, 24.1 [+ or -] 1.5 yr) performed intermittent isometric isometric /iso·met·ric/ (-met´rik) maintaining, or pertaining to, the same measure of length; of equal dimensions.
1. handgrip contractions at a target force of 50% of maximal voluntary contraction (MVC (Model View Controller) An architecture for building applications that separate the data (model) from the user interface (view) and the processing (controller). ) for 5 s followed by 5 s rest until task failure. Rate of fatigue was calculated from MVCs taken every 2 min during exercise, and recovery of muscle strength was measured in 5 min increments until 45 min post-task failure. Forearm muscle strength was less for women than men (W: 341.5 [+ or -] 11.9 N; M: 480.2 [+ or -] 28.0 N; p [less than or equal to] 0.05). No gender difference was present in time to task failure (W: 793.3 [+ or -] 92.5 s; M: 684.8 [+ or -] 76.3 s) or in the decrease in muscle force generating capacity at task failure (W: -47.6 [+ or -] 1.0%; M: -49.9 [+ or -] 1.3%). Rate of muscle fatigue was found to be similar between women and men (W: -3.6 [+ or -] 0.5% x [min.sup.-1]; M: -4.3 [+ or -] 0.6% x [min.sup.-1]) and no gender difference was found in the recovery of muscle strength following task failure. In summary, no gender difference was found in the fatigability fatigability /fat·i·ga·bil·i·ty/ (fat?i-gah-bil´it-e) easy susceptibility to fatigue.
easy susceptibility to fatigue. of the forearm muscles during intermittent submaximal handgrip contractions, independent of muscle strength.
Key words: Muscle fatigue, gender differences, handgrip.
The underlying events leading to muscle fatigue, defined as a decrease in the maximum force-generating capacity of muscle (Bigland-Ritchie et al., 1978), continue to be examined because of the limiting effect that muscle fatigue has on exercise tolerance in both health and disease. Previous studies have shown that gender differences exist in skeletal muscle fatigue (for review see Hicks et al., 2001), with a number of studies demonstrating untrained, healthy women to experience a lower decrement To subtract a number from another number. Decrementing a counter means to subtract 1 or some other number from its current value. in muscle strength following an exercise task and/or perform the task for a longer period of time as compared to untrained, healthy men (Fulco et al., 1999; Hunter and Enoka, 2001; Hunter et al., 2004; Russ and Kent-Braun, 2003; West et al., 1995). This general finding has often been described as a greater relative resistance to muscle fatigue in women as compared to men, however, this is not a universal finding (Ditor and Hicks, 2000; Kent-Braun et al., 2002).
Handgrip contractions has been widely used in studies examining forearm muscle fatigue (Ettinger et al., 1996; Pitcher and Miles, 1997) and the forearm blood flow response to exercise (Barnes, 1980; Kagaya and Ogita, 1992). The main forearm muscles involved in handgrip contractions are the flexor flexor /flex·or/ (flek´ser)
1. causing flexion.
2. a muscle that flexes a joint.
flexor retina´culum see entries under retinaculum. digitorium profundus, flexor digitorium superficialis, and the flexor and extensor extensor /ex·ten·sor/ (-ser) [L.]
1. causing extension.
2. a muscle that extends a joint.
A muscle that extends or straightens a limb or body part. carpi car·pi
Plural of carpus. . Gender differences in the fatigability of the forearm muscles have been previously investigated during sustained isometric handgrip contractions. During this type of contraction it has been found that untrained women exhibit a longer endurance time The total time for which any specified endurance speed of a ship can be maintained. If this value is dependent on factors other than fuel, it shall be so indicated. than untrained men throughout a range of intensities (30-75% MVC) (Petrofsky et al., 1975; West et al., 1995). However, gender differences in the fatigability of the forearm muscles during intermittent handgrip exercise has not been examined, but would be of interest to the sports medicine sports medicine, branch of medicine concerned with physical fitness and with the treatment and prevention of injuries and other disorders related to sports. Knee, leg, back, and shoulder injuries; stiffness and pain in joints; tendinitis; "tennis elbow"; and specialist since intermittent handgrip contractions are utilized in physical activities such as sport climbing Sport climbing is a style of rock climbing that relies on permanent anchors fixed to the rock, especially bolts, for protection. Sport climbing places an emphasis on gymnastic ability, strength and endurance, while virtually eliminating the need to place protection while climbing. (Watts and Drobish, 1998) and racquet sports (Chow et al., 1999), and overuse overuse Health care The common use of a particular intervention even when the benefits of the intervention don't justify the potential harm or cost–eg, prescribing antibiotics for a probable viral URI. Cf Misuse, Underuse. of the forearm muscles has been previously described to result in musculoskeletal disorders Musculoskeletal disorders (MSDs) can affect the body's muscles, joints, tendons, ligaments and nerves. Most-work related MSDs develop over time and are caused either by the work itself or by the employees' working environment. (Bilic et al., 2001).
The observed gender difference in forearm muscle fatigue following sustained isometric handgrip exercise can be attributed to limited blood flow by intramuscular intramuscular /in·tra·mus·cu·lar/ (-mus´ku-ler) within the muscular substance.
adj. Abbr. IM
Within a muscle. pressure in stronger men contracting at a greater absolute force but similar relative contraction intensity as weaker women. Reduced blood flow contributes to muscle fatigue by means of decreased delivery of oxygen and glucose, and also by insufficient removal of metabolic byproducts ([H.sup.+], [P.sub.i], [H.sub.2]P[O.sub.4]) associated with muscle fatigue (Fitts, 1994). In contrast, the hyperemic hyperemic,
adj having a large volume of blood in any given place in the body. response that occurs between intermittent handgrip contractions minimizes the effect of mechanical compression on limiting forearm muscle blood flow, thus a different mechanism is responsible for the gender difference in muscle fatigue that has been reported during intermittent isometric exercise isometric exercise
Exercise performed by the exertion of effort against a resistance that strengthens and tones the muscle without changing the length of the muscle fibers. (Fulco et al., 1999; Gonzales and Scheuermann, 2006; Hunter et al., 2004). Using the fatigue protocol described by Lewis and Fulco (1998), we have recently shown untrained women have a slower rate of inspiratory in·spi·ra·to·ry
Of, relating to, or used for the drawing in of air.
pertaining to or used in the inspiration of air into the lungs. muscle fatigue than untrained men during intermittent isometric exercise (Gonzales and Scheuermann, 2006), consistent with findings in the adductor pollicis muscle The adductor pollicis muscle is a muscle in the hand that functions to adduct the thumb. It has two heads: transverse and oblique. Structure
Oblique headThe oblique head (occasionally known as adductor obliquus pollicis (Fulco et al., 1999). Since the activation of muscle is largely dependent on the task and has been shown to vary between muscles that contribute to a functional load (Clark et al., 2003; Hunter et al., 2003), we postulated that gender differences in forearm muscle fatigue from intermittent handgrip exercise may be different than skeletal muscle groups comprised of a single muscle like the adductor pollicis muscle (Fulco et al., 1999) or the diaphragm (Gonzales and Scheuermann, 2006). To investigate this hypothesis, we recruited the same subjects recently examined during an inspiratory muscle fatigue study (Gonzales and Scheuermann, 2006) and followed the same protocol during intermittent isometric handgrip exercise to determine if women will demonstrate a slower rate of forearm muscle fatigue and/or a longer duration to task failure than men as previously reported (Fulco et al., 1999; Gonzales and Scheuermann, 2006).
Twenty-two healthy, untrained women (n = 11) and men (n = 11) provided written informed consent after being explained all experimental procedures, the exercise protocol, and possible risks associated with participation in the study. Women subjects were interviewed by the investigator and menstrual cycle menstrual cycle
The recurring cycle of physiological changes in the uterus, ovaries, and other sexual structures that occur from the beginning of one menstrual period through the beginning of the next. history was determined. All testing occurred during the early follicular phase follicular phase
The phase during which the ovarian follicle develops during the menstrual cycle.
follicular phase Proliferative phase, see there (between days 1-5) of their menstrual cycle, when both estradiol estradiol /es·tra·di·ol/ (es?trah-di´ol) (es-tra´de-ol) the most potent estrogen in humans; pharmacologically, it is often used in the form of its esters (e.g., e. cypionate, e. and progesterone progesterone (prōjĕs`tərōn'), female sex hormone that induces secretory changes in the lining of the uterus essential for successful implantation of a fertilized egg. levels are believed to be lowest. The experimental protocol was approved by the Human Subjects Research and Review Committee at the University of Toledo National recognition
In its 125-year history UT has garnered several national accolades. The University’s programs, faculty and facilities have been highlighted in the media, including and is in accordance with guidelines set forth by the Declaration of Helsinki For the political accords, see .
. There is also another Declaration of Helsinki, dealing with the Information Society. Introduction
The Declaration of Helsinki, was developed by the World Medical Association .
Separate analyses were performed retrospectively in a subgroup of women (n = 5) and men (n = 5) that were matched for resting forearm muscle MVC force (i.e. absolute strength). Previous studies have found absolute strength to be an independent factor contributing to skeletal muscle fatigue during isometric muscle contractions isometric muscle contraction (ī´sōmet´rik),
n See contraction, muscle, isometric. (Hunter and Enoka, 2001). Therefore, a strength-matched gender comparison would determine if any gender difference found in the fatigability of the forearm muscles was due to differences in absolute strength.
Subjects reported to the Cardiopulmonary cardiopulmonary /car·dio·pul·mo·nary/ (kahr?de-o-pool´mah-nar-e) pertaining to the heart and lungs.
Of, relating to, or involving both the heart and the lungs. and Metabolism Research Laboratory at the University of Toledo on two separate occasions with no less than 48 h between testing sessions. Each subject was instructed to consume only a light meal, and to abstain from abstain from
verb refrain from, avoid, decline, give up, stop, refuse, cease, do without, shun, renounce, eschew, leave off, keep from, forgo, withhold from, forbear, desist from, deny yourself, kick ( vigorous exercise vigorous exercise A form of exercise that is intense enough to cause sweating and/or heavy breathing/ and/or ↑ heart rate to near maximum; VE is formally defined as that which requires > 6 METs; there is a graded inverse relationship between total physical and caffeinated beverages for [greater than or equal to] 12 h prior to arriving for testing. Exercise testing was performed at approximately the same time of the day for each subject.
Preliminary exercise testing was performed to both familiarize the subject with the testing procedures and for the determination of their achieved maximal aerobic capacity (V[O.sub.2,peak]) which we used as an indicator of overall fitness level. The highest mean oxygen uptake averaged over a 30 s interval was defined as V[O.sub.2,peak]. Cardiopulmonary testing was performed on an electrically braked cycle ergometer ergometer /er·gom·e·ter/ (er-gom´e-ter) a dynamometer.
bicycle ergometer an apparatus for measuring the muscular, metabolic, and respiratory effects of exercise. (Excalibur Sport, Lode, The Netherlands). The maximal exercise test involved 5 min of low intensity (20 W) cycling followed by a progressive increase in exercise intensity to volitional vo·li·tion
1. The act or an instance of making a conscious choice or decision.
2. A conscious choice or decision.
3. The power or faculty of choosing; the will. fatigue. The work rate was increased as a ramp function The ramp function is an elementary unary real function, easily computable as the mean of its independent variable and its absolute value.
This function is applied in engineering (e.g., in the theory of DSP). at a rate of 20 and 25 W x [min.sup.-1] for women and men, respectively. Subjects were instructed to maintain a constant pedal cadence selected by the subject and were aided by both visual feedback and verbal encouragement. Following a cool down period, subjects were instructed on the testing protocol to be conducted during the second study session, and were allowed sufficient time to practice all tasks. During the second study session, subjects performed submaximal intermittent handgrip exercise to task failure.
Pulmonary gas exchange
Pulmonary gas exchange and expired ventilation were measured using an automated open-circuit metabolic measurement system (Jaeger jaeger (yā`gər), common name for several members of the family Stercorariidae, member of a family of hawklike sea birds closely related to the gull and the tern. The skua is also a member of this family. , Oxycon Alpha, Germany). Expired gas ex·pired gas
1. A gas that has been expired from the lungs.
2. See mixed expired gas. flows were measured using a turbine. The flow signal was integrated to yield a volume signal that was calibrated cal·i·brate
tr.v. cal·i·brat·ed, cal·i·brat·ing, cal·i·brates
1. To check, adjust, or determine by comparison with a standard (the graduations of a quantitative measuring instrument): with a syringe of known volume (3.0 L). Prior to each exercise test, the [O.sub.2] and C[O.sub.2] analyzers were calibrated using gases of known concentrations. Corrections for ambient temperature Outside temperature at any given altitude, preferably expressed in degrees centigrade. and water vapor were made for conditions measured near the mouth.
Forearm muscle strength and fatigue
Prior to the exercise protocol, subjects performed two maximal voluntary contractions (MVC), separated by 2 min of rest, using a handgrip dynamometer dynamometer /dy·na·mom·e·ter/ (di?nah-mom´e-ter) an instrument for measuring the force of muscular contraction.
An instrument for measuring the degree of muscular power. for the determination of maximal forearm strength in kilograms (Takei, Japan). Following 5 min of rest, the subjects performed two additional MVCs, separated by 2 min of rest, using a handgrip dynamometer connected to a data acquisition system (ADInstruments, MCT See Microsoft certification. 300/D, Grand Junction Grand Junction, city (1990 pop. 29,034), seat of Mesa co., W Colo., at the junction of the Gunnison and Colorado rivers; inc. 1891. The shipping and processing center of a large ranch and irrigated farm region, it also serves the area's uranium, oil shale, gas, and , CO) that allowed for the force displacement to be shown on-screen on·screen or on-screen
adj. & adv.
1. As shown on a movie, television, or display screen.
2. Within public view; in public. for subject viewing. For test-retest reliability test-retest reliability Psychology A measure of the ability of a psychologic testing instrument to yield the same result for a single Pt at 2 different test periods, which are closely spaced so that any variation detected reflects reliability of the instrument of MVC force, an intraclass correlation In statistics, the intraclass correlation (or the intraclass correlation coefficient) is a measure of correlation, consistency or conformity for a data set when it has multiple groups. coefficient of 0.98 was obtained (CI = 0.96-0.99). The highest force displacement was scaled so that the peak force was 100% and the target force for the fatigue protocol (i.e. 50% MVC) was clearly indicated on the monitor.
Handgrip exercise performed by the dominant arm was utilized to elicit forearm muscle fatigue using an approach previously described by Lewis and Fulco (1998). While seated with the elbow at approximately a 90[degrees] angle, subjects performed repeated contractions at 50% of their relative MVC for 5 s followed by 5 s of relaxation with the forearm in the neutral position. The handgrip dynamometer used in the present study did not allow adjustment for different hand sizes with a grip span of 5 cm. We do not believe this influenced the results of the present study since fatigue of the forearm muscle flexor digitorum superficialis, as inferred from EMG EMG
A diagnostic test that records the electrical activity of muscles. frequency shifts, has been shown not to change as a function of grip size (Blackwell et al., 1999). Subjects visually monitored force generation during the protocol and were aided by verbal encouragement. Subjects were asked to perform a single maximal effort every 2 min in order to record the decline in maximal force production. Task failure was determined as the time at which the subject was unable to produce a MVC greater than 50% of their resting MVC during each maximal effort or was unable to reach 50% of their MVC during three consecutive contractions during intermittent exercise. Upon reaching task failure, the subjects were instructed to perform two MVCs immediately and at 5 min increments up to 30 min post-task failure with the last measurement taken at 45 min post-task failure in order to monitor recovery of forearm muscle strength.
The rate of muscle fatigue (i.e. slope) in Newtons per minute was determined for each subject by linear regression Linear regression
A statistical technique for fitting a straight line to a set of data points. using the maximal force measurements that were obtained every 2 min during the fatiguing task. The individual slopes were averaged to provide group mean values for each gender. Comparison between gender in demographic information, time to task failure, and rate of fatigue were performed by Student t-tests. Bivariate bi·var·i·ate
Mathematics Having two variables: bivariate binomial distribution.
Adj. 1. correlations were performed to evaluate relationships between variables. Gender differences in forearm muscle force were analyzed using a repeated measures ANOVA anova
see analysis of variance.
ANOVA Analysis of variance, see there design with gender and time as the main effects. All values are reported as Mean [+ or -] SE and significance was set a priori a priori
In epistemology, knowledge that is independent of all particular experiences, as opposed to a posteriori (or empirical) knowledge, which derives from experience. at p [less than or equal to] 0.05.
[FIGURE 1 OMITTED]
The physical characteristics of the subjects are reported in Table 1. No attempt was made to recruit women and men with similar forearm muscle strength in the present study. Therefore, the mean age of women and men subjects was similar, but on average, women were shorter, had a lower body mass and V[O.sub.2,peak] compared to men. Subjects reported to be sedentary or involved in regular recreational activity, but none were considered to be highly trained (< 42 ml x [kg.sup.-1] x [min.sup.-1]).
Forearm muscle fatigue
The maximal isometric force generated by women at rest was less than men (F: 341.5 [+ or -] 11.9 N; M: 488.5 [+ or -] 31.3 N; p [less than or equal to] 0.05) indicating that men had significantly greater forearm muscle strength than women. Body surface area, as calculated by the Mosteller formula [[Height (cm) x Weight (kg)/3600].sup.1/2], was significantly correlated with resting MVC force for men and also when data from women and men were pooled together (F: r = 0.11, p [greater than or equal to] 0.05; M: r = 0.82, pooled: r = 0.75, p [less than or equal to] 0.01). The greater absolute force for men persisted throughout the handgrip exercise protocol (Figure 1a).
Early fatigue of the forearm muscles was assessed after 2 min of intermittent handgrip exercise. The initial decline in maximal force generation was similar between women and men (19.5 [+ or -] 2.4% and 18.6 [+ or -] 2.5% decrease from resting MVC force for women and men, respectively) (Figure 2a). The rate of forearm muscle fatigue, determined by the slope of the change in MVC force during handgrip exercise, was slower in women than men (F: -12.2 [+ or -] 1.8 N x [min.sup.-1], M: -21.8 [+ or -] 4.4 N x [min.sup.-1], p [less than or equal to] 0.05), and was significantly correlated with resting forearm muscle strength (pooled: r = 0.62, p [less than or equal to] 0.01). However, when the rate of forearm muscle fatigue was expressed relative to resting MVC force, thereby correcting for differences in absolute force, the relative rate of fatigue was similar between genders (F: -3.6 [+ or -] 0.5% decrease from resting MVC force per min; M: -4.3 [+ or -] 0.6% decrease from resting MVC force per min) (Figure 3).
As expected from the fatigue protocol, the decrease in maximal force development at task failure was similar between women and men (F: 47.6 [+ or -] 1.0% decrease from resting MVC force; M: 49.9 [+ or -] 1.3% decrease from resting MVC force). Time to task failure was not significantly different between the genders (F: 793.3 [+ or -] 92.5 s; M: 684.8 [+ or -] 76.2 s) and was highly correlated with the absolute change in the rate of muscle fatigue (F: r = 0.85, M: r = 0.84, pooled: r = 0.74, p [less than or equal to] 0.01). The relationship between time to task failure and pooled data for the absolute and relative changes in the rate of fatigue was well described by an exponential decay Noun 1. exponential decay - a decrease that follows an exponential function
decay, decline - a gradual decrease; as of stored charge or current (absolute: r = 0.87, y = 7.7 + [181.3.sup.-0.005x]; relative: r = 0.96, y = 1.8 + [20.7.sup.-0.0037x]) with women and men demonstrating a similar response (Figure 4).
[FIGURE 2 OMITTED]
Recovery of maximal force generating capacity was similar between women and men (10 min) when absolute changes in force were analyzed (Figure 1a). When expressed relative to resting MVC force, a 2-way ANOVA found no main effect for gender or an interaction between gender and time. A one-way ANOVA analyzed for time within each gender found women and men to return to maximal force generating capacity at 25 min and 15 min post-task failure, respectively (Figure 1b).
Gender comparison when matched for strength
Women and men matched for resting MVC force had similar physical characteristics (see Table 1).Resting MVC force was 376.6 [+ or -] 10.6 N and 407.8 [+ or -] 27.3 N for women and men, respectively (p [greater than or equal to] 0.05). After 2 min of handgrip exercise, women and men resulted in a similar decrease in forearm muscle strength (F: 21.4 [+ or -] 3.9% drop from resting MVC force; M: 18.2 [+ or -] 1.3% drop from resting MVC force) (Figure 2b). The rate of forearm muscle fatigue during handgrip exercise was similar for women and men when analyzed for both absolute (F: -15.0 [+ or -] 3.1 N x [min.sup.-1]; M: -14.3 [+ or -] 3.3 N x [min.sup.-1]) and relative (F: -3.9 [+ or -] 0.8% drop from resting MVC force per min; M: -3.4 [+ or -] 0.7% drop from resting MVC force per min) changes (Figure 3). At task failure, both women and men demonstrated forearm muscle fatigue in accordance with the exercise protocol (F: 47.1 [+ or -] 2.0% decrease from resting MVC force; M: 48.8 [+ or -] 1.7% decrease from resting MVC force) (Figure 2b). Time to task failure was similar between the strength-matched genders (F: 706.6 [+ or -] 117.0 s; M: 831.8 [+ or -] 118.7 s), and lastly, recovery of maximal force generating capacity returned to resting MVC force within 5 min following task failure in both women and strength-matched men.
To our knowledge, this is the first study to compare the fatigability of the forearm muscles during repeated submaximal handgrip contractions between women and men. Based on previous gender-based comparisons involving intermittent isometric contractions performed by other skeletal muscles Skeletal muscles
Muscles that move the skeleton. All of the muscles under voluntary control are skeletal muscles.
Mentioned in: Creatine Kinase Test (Fulco et al., 1999; Gonzales and Scheuermann, 2006; Hunter et al., 2004), we hypothesized that women would exhibit a slower rate of forearm muscle fatigue and result in a longer time to task failure than men (i.e. a greater fatigue resistance). In contrast to our hypotheses, the present study found time to task failure and rate of forearm muscle fatigue to be similar between genders, in both unmatched and matched for strength comparisons. These results suggest that a similar fatigue process occurs for women and men during repeated isometric contractions performed by the forearm muscles.
[FIGURE 3 OMITTED]
The forearm muscles are a highly recruited muscle group utilized in physical activities such as tennis (Chow et al., 1999) and sport climbing (Watts and Drobish, 1998). Moreover, the forearm muscles are used frequently in daily functional activities such that handgrip strength is used as an indicator of overall muscle strength and has been reported to highly predict disability with ageing (Rantanen et al., 1999). The frequent use of the forearm muscles may result in a different neuromuscular neuromuscular /neu·ro·mus·cu·lar/ (-mus´ku-ler) pertaining to nerves and muscles, or to the relationship between them.
1. activation pattern than those used by other skeletal muscles. In addition, the activation pattern within a muscle group has been shown to vary between muscles that comprise the functional group. Hunter et al. (2003) has demonstrated that activation among the elbow flexor muscles differ across time during a fatiguing contraction and also within the same muscle during different tasks. Chow et al. (1999) has also demonstrated greater activation of the extensor carpi radialis Extensor carpi radialis can refer to:
Differences in muscle morphology and hence substrate utilization is a mechanism that partly explains the inconsistent findings between the present study and those found by others examining the adductor adductor /ad·duc·tor/ (ah-duk´tor) [L.] that which adducts, as the adductor muscle.
n. pollicis (Fulco et al., 1999) and inspiratory muscles (Gonzales and Scheuermann, 2006). The adductor pollicis and inspiratory muscles are both highly oxidative muscles comprised of a large proportion of fatigue resistant Type I fibers. On the other hand, the forearm muscles (flexor digitorium muscles) have a generally equal proportion of Type I and II fibers (Johnson et al., 1973). Since women have been shown to have a greater potential for oxidative phosphorylation oxidative phosphorylation: see phosphorylation. relative to glycolysis glycolysis (glīkŏl`ĭsĭs), term given to the metabolic pathway utilized by most microorganisms (yeast and bacteria) and by all "higher" animals (including humans) for the degradation of glucose. than men (Simoneau et al., 1985), it reasons that women would experience a slower rate of fatigue than men during exercise performed by an oxidative muscle. In contrast, the even distribution of fiber types in the forearm muscles would suggest that one metabolic pathway would not be relied heavily upon for ATP ATP: see adenosine triphosphate.
in full adenosine triphosphate
Organic compound, substrate in many enzyme-catalyzed reactions (see catalysis) in the cells of animals, plants, and microorganisms. production throughout exercise. This is supported by calculations from [sup.31]P magnetic spectroscopy measurements taken from the flexor digitorum superficialis muscle Flexor digitorum superficialis (flexor digitorum sublimis) is an extrinsic flexor muscle of the fingers at the proximal interphalangeal joints. The bulk of the muscle is in the intermediate layer of the anterior compartment of the forearm. that showed equal relative total contributions of PCr hydrolysis hydrolysis (hīdrŏl`ĭsĭs), chemical reaction of a compound with water, usually resulting in the formation of one or more new compounds. , glycolysis, and oxidative phosphorylation to ATP production between women and men during 3 min of intermittent finger flexion flexion /flex·ion/ (flek´shun) the act of bending or the condition of being bent.
1. The act of bending a joint or limb in the body by the action of flexors.
2. exercise (Mattei et al., 1999).
[FIGURE 4 OMITTED]
In the present study relative forearm muscle force fell by a similar magnitude between women and men during the first 2 min of intermittent handgrip exercise. Mattei et al. (1999) has provided evidence from [sup.31]P magnetic spectroscopy measurements to indicate that forearm muscle activity has a preference for anaerobic anaerobic /an·aer·o·bic/ (an?ah-ro´bik)
1. lacking molecular oxygen.
2. growing, living, or occurring in the absence of molecular oxygen; pertaining to an anaerobe. pathways during the first minute of intermittent forearm muscle contractions in both women and men. In addition, Pitcher and Miles (Pitcher and Miles, 1997) have shown similar decreases in forearm muscle force during the first 2 min of intermittent handgrip exercise between ischemic Ischemic
An inadequate supply of blood to a part of the body, caused by partial or total blockage of an artery.
Mentioned in: Antiangiogenic Therapy, Subarachnoid Hemorrhage, Ventricular Fibrillation
ischemic and free-flow circulation conditions suggesting the primary use of anaerobic metabolic energy pathways. Taken together, these findings indicate that the similar decrease in forearm muscle force between women and men after 2 min of intermittent exercise was due to similar metabolic pathways utilized by each gender, which were likely anaerobic in nature.
Interruption of muscle blood flow by means of significant intramuscular pressure has been extensively studied during sustained isometric muscle contractions, many of which have been performed using handgrip exercise (Barnes, 1980; Kagaya and Homma, 1997). Limited muscle blood flow contributes to muscle fatigue by decreased delivery of oxygen and glucose and also the removal of metabolic byproducts ([H.sup.+], [P.sub.i], [H.sub.2]P[O.sub.4]) associated with muscle fatigue (Fitts, 1994). This fatigue mechanism has been attributed to be a cause of the reduced time to task failure seen in men during sustained handgrip exercise when blood flow is thought to be limited (Petrofsky et al., 1975; West et al., 1995). In the present study, men generated greater absolute forearm muscle force than women, and thereby, likely generated more metabolic by-products than women (Ettinger et al., 1996). However, women and men showed a similar relative rate of forearm muscle fatigue during intermittent forearm muscle contractions, with no gender difference observed in the absolute change in rate of fatigue when matched for absolute force. This suggests that forearm muscle blood flow was sufficient to prevent the local accumulation of metabolic byproducts during intermittent isometric handgrip exercise. The hyperemic response shown to occur between intermittent handgrip contractions likely minimizes the effect of mechanical compression on forearm muscle blood flow (Kagaya and Ogita, 1992), which may prevent a significant reduction in forearm blood flow.
Although forearm muscle mass was not measured in the present study, men were on average taller and heavier (i.e. 10% larger body surface area) than women. Although this does not completely explain the 25% greater forearm muscle strength in men as compared to women, a significant correlation between body surface area and resting MVC force was observed (pooled: r = 0.75, p < 0.01). Thus, it is likely that men also had a larger forearm muscle mass than women in order to generate the greater forearm muscle force. In spite of this, women and men had a similar relative rate of decline in forearm muscle strength and resulted in a similar time to task failure during repeated handgrip exercise. This is consistent with the report by West et al. (1995) that found low correlations between resting MVC force and endurance time during sustained isometric handgrip exercise in women and men of different forearm strength. The present study extends this finding to intermittent handgrip exercise in that time to task failure was not correlated with forearm muscle strength (pooled data, r = 0.08). These results are consistent with the view that absolute force is not a primary factor influencing forearm muscle fatigability during handgrip exercise.
Following task failure, both women and men returned to resting MVC force within 10 min. When strength measurements were analyzed relative to resting MVC force, no difference in recovery was found between women and men. However, analysis within each gender showed women and men to return to resting MVC force within 25 min and 15 min following task failure, respectively. Although this could be interpreted as a greater forearm muscle fatigue for women as compared to men, the fact that each gender resulted in a similar relative rate of forearm muscle fatigue and time to task failure suggests that muscle fatigue was equal between women and men. The prolonged recovery exhibited by women could be due to a number of factors. For instance, women in the present study had a 15% lower V[O.sub.2peak] (i.e. aerobic capacity) than men which may have translated to a reduced ability to restore MVC force (Hakkinen and Myllyla, 1990). Nevertheless, it is important to recognize that women and men matched for resting MVC force showed a similar recovery of forearm muscle strength following task failure, confirming that there was no gender difference in the magnitude of forearm muscle fatigue during intermittent handgrip exercise. We cannot, however, speak to the initial recovery (1-3 min) of MVC force which may have been different between women and men as been reported in other skeletal muscles during intermittent contractions (Fulco et al., 1999; Kent-Braun et al., 2002).
In conclusion, women do not exhibit a greater ability to resist forearm muscle fatigue than men during submaximal intermittent handgrip exercise. Instead, the present study found women and men to exhibit a similar exercise tolerance during repeated forearm muscle contractions. This finding was irrespective of irrespective of
Without consideration of; regardless of.
preposition despite absolute force, indicating that maximal handgrip strength had no influence on forearm muscle fatigability during handgrip exercise. These findings indicate that maximal handgrip strength is not a key determinant of exercise tolerance during relative isometric forearm exercise. Indeed, Mermier et al. (Mermier et al., 2000) recently reported similar static (50% MVC) handgrip endurance times between trained women and men sport climbers in spite of the men climbers having greater maximum handgrip strength than the women climbers. The precise mechanisms that cause the similar fatigue process for women and men during repeated isometric handgrip contractions has yet to be elucidated, but would be of great interest considering the gender differences in muscle fatigue observed in other skeletal muscles.
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* The aim of the present study was to determine if gender differences exist in forearm muscle fatigue during intermittent isometric handgrip contractions.
* Both unmatched and matched for strength gender comparisons found women and men to exhibit a similar exercise tolerance, rate of fatigue, and recovery of handgrip force following repeated forearm muscle contractions.
* These results indicate that maximal handgrip strength is not a key determinant of exercise tolerance during intermittent isometric forearm exercise performed at a moderate relative contraction intensity.
Joaquin U. GONZALES
PhD Candidate, Department of Kinesiology,
The University of Toledo, Toledo,
Muscle fatigue, endothelial endothelial /en·do·the·li·al/ (-the´le-al) pertaining to or made up of endothelium.
A layer of cells that lines the inside of certain body cavities, for example, blood vessels. function,
blood flow during exercise
Barry W. SCHEUERMANN
Assistant Professor, Department of Kinesiology,
The University of Toledo, Toledo,
Muscle fatigue, metabolism, endothelial
function, blood flow during exercise
Joaquin U. Gonzales and Barry W. Scheuermann ([mail])
Cardiopulmonary and Metabolism Research Laboratory, Department of Kinesiology, The University of Toledo, Toledo, Ohio
([mail]) Barry W. Scheuermann, PhD
Assistant Professor, Department of Kinesiology, College of
Health and Human Services Noun 1. Health and Human Services - the United States federal department that administers all federal programs dealing with health and welfare; created in 1979
Department of Health and Human Services, HHS , The University of Toledo, Toledo,
Ohio 43607, USA.
Table 1. Subject characteristics. Values are means ([+ or -]SE). UNMATCHED Variable Women (n=11) Men (n=11) Age (yrs) 23.1 (2.0) 24.0 (2.0) Height (m) 1.69 (.02) * 1.76 (.02) Weight (kg) 65.8 (3.6) * 78.1 (4.4) Body surface area ([m.sup.2]) 1.7 (.1) * 1.9 (.1) [Vo.sub.2,peak] 34.8 (1.6) * 41.2 (2.5) (ml x kg x [min.sup.-1]) Resting MVC force (N) 341.5 (11.9) * 488.5 (31.3) MVC force (N) at task failure 179.7 (7.6) * (#) 242.7 (12.8) (#) Time to task failure (s) 793.3 [+ or -] 92.5 684.8 (76.2) MATCHED Variable Women (n=5) Men (n=5) Age (yrs) 22.4 (2.0) 24.6 (1.0) Height (m) 1.71 (.03) 173.7 (2.4) Weight (kg) 74.0 (6.3) 71.2 (4.6) Body surface area ([m.sup.2]) 1.9 (.1) 1.8 (.1) [Vo.sub.2,peak] 34.6 (3.4) 39.8 (1.3) (ml x kg x [min.sup.-1]) Resting MVC force (N) 376.6 (10.6) 407.8 (27.3) MVC force (N) at task failure 199.0 (8.1) (#) 208.7 (16.0) (#) Time to task failure (s) 706.6 (117.0) 831.8 (118.7) * significant gender difference within each respective group (p < 0.05). (#) significant difference between resting MVC force and respective value at task failure (p < 0.05).