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Muscular adaptations in response to three different resistance-training regimens: Specificity of repetition maximum training zones

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Thirty-two untrained men [mean (SD) age 22.5 (5.8) years, height 178.3 (7.2) cm, body mass 77.8 (11.9) kg] participated in an 8-week progressive resistance-training program to investigate the "strength-endurance continuum". Subjects were divided into four groups: a low repetition group (Low Rep, n = 9) performing 3-5 repetitions maximum (RM) for four sets of each exercise with 3 min rest between sets and exercises, an intermediate repetition group (Int Rep, n = 11) performing 9-11 RM for three sets with 2 min rest, a high repetition group (High Rep, n = 7) performing 20-28 RM for two sets with 1 min rest, and a non-exercising control group (Con, n = 5). Three exercises (leg press, squat, and knee extension) were performed 2 days/week for the first 4 weeks and 3 days/week for the final 4 weeks. Maximal strength [one repetition maximum, 1RM), local muscular endurance (maximal number of repetitions performed with 60% of 1RM), and various cardiorespiratory parameters (e.g., maximum oxygen consumption, pulmonary ventilation, maximal aerobic power, time to exhaustion) were assessed at the beginning and end of the study. In addition, pre- and post-training muscle biopsy samples were analyzed for fiber-type composition, cross-sectional area, myosin heavy chain (MHC) content, and capillarization. Maximal strength improved significantly more for the Low Rep group compared to the other training groups, and the maximal number of repetitions at 60% 1RM improved the most for the High Rep group. In addition, maximal aerobic power and time to exhaustion significantly increased at the end of the study for only the High Rep group. All three major fiber types (types I, IIA, and IIB) hypertrophied for the Low Rep and Int Rep groups, whereas no significant increases were demonstrated for either the High Rep or Con groups. However, the percentage of type IIB fibers decreased, with a concomitant increase in IIAB fibers for all three resistance-trained groups. These fiber-type conversions were supported by a significant decrease in MHCIIb accompanied by a significant increase in MHCIIa. No significant changes in fiber-type composition were found in the control samples. Although all three training regimens resulted in similar fiber-type transformations (IIB to IIA), the low to intermediate repetition resistance-training programs induced a greater hypertrophic effect compared to the high repetition regimen. The High Rep group, however, appeared better adapted for submaximal, prolonged contractions, with significant increases after training in aerobic power and time to exhaustion. Thus, low and intermediate RM training appears to induce similar muscular adaptations, at least after short-term training in previously untrained subjects. Overall, however, these data demonstrate that both physical performance and the associated physiological adaptations are linked to the intensity and number of repetitions performed, and thus lend support to the "strength-endurance continuum".
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European Journal of Applied Physiology
DOI 10.1007/s00421-002-0681-6
Original Article
Muscular adaptations in response to three different
resistance-training regimens: specificity of repetition
maximum training zones
Gerson E. R. Campos · Thomas J. Luecke · Heather K. Wendeln · Kumika Toma · Fredrick C.
Hagerman · Thomas F. Murray · Kerry E. Ragg · Nicholas A. Ratamess · William J. Kraemer ·
Robert S. Staron( )
G.E.R. Campos · T.J. Luecke · H.K. Wendeln · K. Toma · F.C. Hagerman · R.S. Staron
Department of Biomedical Sciences, College of Osteopathic Medicine, Ohio University, Irvine Hall,
rm 430, Athens, OH 45701, USA
T.F. Murray
Com-Admin and Diagnostic Services, College of Health and Human Services, Ohio University,
Athens, OH 45701, USA
K.E. Ragg
Student Health Service, Ohio University, Athens, OH 45701, USA
N.A. Ratamess · W.J. Kraemer
Human Performance Laboratory, Department of Kinesiology, The University of Connecticut, Storrs,
CT 06269, USA
E-mail: staron@ohio.edu
Phone: +1-740-5932409
Fax: +1-740-5972778
Accepted: 14 June 2002 / Published online:
Abstract. Thirty-two untrained men [mean (SD) age 22.5 (5.8) years, height 178.3 (7.2) cm, body
mass 77.8 (11.9) kg] participated in an 8-week progressive resistance-training program to investigate
the "strength-endurance continuum". Subjects were divided into four groups: a low repetition group
(Low Rep, n=9) performing 3-5 repetitions maximum (RM) for four sets of each exercise with 3 min
rest between sets and exercises, an intermediate repetition group (Int Rep, n=11) performing 9-11 RM
for three sets with 2 min rest, a high repetition group (High Rep, n=7) performing 20-28 RM for two
sets with 1 min rest, and a non-exercising control group (Con, n=5). Three exercises (leg press, squat,
and knee extension) were performed 2 days/week for the first 4 weeks and 3 days/week for the final
4 weeks. Maximal strength [one repetition maximum, 1RM), local muscular endurance (maximal
- 1 -
number of repetitions performed with 60% of 1RM), and various cardiorespiratory parameters (e.g.,
maximum oxygen consumption, pulmonary ventilation, maximal aerobic power, time to exhaustion)
were assessed at the beginning and end of the study. In addition, pre- and post-training muscle biopsy
samples were analyzed for fiber-type composition, cross-sectional area, myosin heavy chain (MHC)
content, and capillarization. Maximal strength improved significantly more for the Low Rep group
compared to the other training groups, and the maximal number of repetitions at 60% 1RM improved
the most for the High Rep group. In addition, maximal aerobic power and time to exhaustion
significantly increased at the end of the study for only the High Rep group. All three major fiber types
(types I, IIA, and IIB) hypertrophied for the Low Rep and Int Rep groups, whereas no significant
increases were demonstrated for either the High Rep or Con groups. However, the percentage of type
IIB fibers decreased, with a concomitant increase in IIAB fibers for all three resistance-trained groups.
These fiber-type conversions were supported by a significant decrease in MHCIIb accompanied by a
significant increase in MHCIIa. No significant changes in fiber-type composition were found in the
control samples. Although all three training regimens resulted in similar fiber-type transformations
(IIB to IIA), the low to intermediate repetition resistance-training programs induced a greater
hypertrophic effect compared to the high repetition regimen. The High Rep group, however, appeared
better adapted for submaximal, prolonged contractions, with significant increases after training in
aerobic power and time to exhaustion. Thus, low and intermediate RM training appears to induce
similar muscular adaptations, at least after short-term training in previously untrained subjects.
Overall, however, these data demonstrate that both physical performance and the associated
physiological adaptations are linked to the intensity and number of repetitions performed, and thus
lend support to the "strength-endurance continuum".
Keywords. Human skeletal muscle - Fiber types - Histochemistry - Capillarization - Myosin heavy
chains
Introduction
Human skeletal muscle is a heterogeneous tissue composed of functionally diverse fiber types (Staron
1997). This mixture of different fiber types enables the muscle to fulfill a variety of functional
demands. An additional unique feature of skeletal muscle is the ability to alter its phenotypic profile in
response to specific stimuli (Pette and Staron 2001). For resistance training, these alterations usually
contribute to significant increases in muscle strength and size (McDonagh and Davies 1984; Tesch
1988; Abernethy et al. 1994). Research in this area has often focused on various combinations of sets
and repetitions to optimize these specific adaptations (Tan 1999). For example, an early study by
Berger (1962) suggested that three sets of 4-8 repetitions produced optimal gains in strength compared
to various other set/repetition combinations. These data suggest that specific muscle-fiber adaptations
are associated with differential strength gains.
It is clear that manipulation of the various acute resistance-training variables (e.g., number of sets,
length of rest periods between sets and exercises, intensity, or load) can stress the muscles in very
different ways. As such, there appears to be a specific relationship between the training stimulus and
the adaptive response. Taking resistance training to various extremes, DeLorme’s classic work (1945)
suggested that a resistance-training program using low repetition/high resistance favored adaptations
for strength/power, whereas training with high repetition/low resistance increased muscular endurance.
Anderson and Kearney (1982) tested DeLorme’s hypothesis by investigating the effects of three very
different resistance programs on strength adaptations. Forty-five college-aged men were randomly
assigned to one of three groups: high resistance/low repetition (three sets of 6-8 repetitions maximum,
RM), medium resistance/medium repetition (two sets of 30-40 RM), and low resistance/high repetition
(one set of 100-150 RM). After 9 weeks of training for 3 days/week, the high resistance/low repetition
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group showed the greatest improvement in maximal strength (one-repetition maximum, 1RM) and the
poorest in relative endurance (maximum number of repetitions using 40% 1RM) compared to the other
two groups. Similar results were obtained in a more recent study using women (Stone and Coulter
1994). This study, although modeled after Anderson and Kearney (1982), used a less extreme
"endurance" protocol for the low-resistance/high repetition group. Forty-five college-aged women
were assigned to one of three groups: high resistance/low repetitions (three sets of 6-8 RM), medium
resistance/medium repetitions (two sets of 15-20 RM), and low resistance/high repetitions (one set of
30-40 RM). After 9 weeks of training for 3 days/week, the high resistance/low repetition training
resulted in greater strength gains, whereas low resistance/high repetition produced greater muscular
endurance gains. From these studies, a "repetition training continuum" (Anderson and Kearney 1982)
or "repetition maximum continuum" (Fleck and Kraemer 1988) has been hypothesized such that the
number of repetitions allowed by the resistance will result in very specific training adaptations.
Although various resistance-training studies have been published demonstrating specific muscular
strength and endurance adaptations (e.g., Anderson and Kearney 1982; Stone and Coulter 1994), there
is scant information concerning specific intramuscular adaptations in response to different set and
repetition combinations. The purpose of the present investigation was to compare the effects of three
different resistance-training programs on adaptations within the vastus lateralis muscle. To this end,
routines at three different points along the theorized strength-endurance continuum were chosen to
investigate and compare specific muscular adaptations. The design of the present study more closely
resembles that of Stone and Coulter (1994), and utilizes a more practical resistance-training regimen
on the endurance end of the continuum compared to that of Anderson and Kearney (1982).
Methods
Subjects
Thirty-two healthy men [mean (SD) age 22.5 (5.8) years, height 178.3 (7.2) cm, body mass 77.8
(11.9) kg] volunteered to participate in the present study. All subjects were informed of the
procedures, risks, and benefits, and signed an informed consent document approved by the Ohio
University Institutional Review Board before participation. Although physically active, all subjects
were considered untrained and had not participated in a regular exercise program for at least 6 months
prior to the start of the study. Twenty-seven healthy men were randomly divided into three training
groups: a low repetition group [Low Rep, n=9; mean (SD) age 21.1 (1.5) years, height 179.8 (6.5) cm],
an intermediate repetition group [Int Rep, n=11; mean (SD) age 20.7 (2.9) years, 179.6 (7.4) cm], and
a high repetition group [High Rep, n=7; mean (SD) age 20.4 (3.5) years, height 174.3 (8.6) cm]. Six
additional individuals served as non-exercising controls (Con). One Con subject began endurance
training during the course of the study and was dropped from the study, leaving a final Con group
comprising five individuals [mean (SD) age 31.6 (9.8) years, height 178.1 (5.5) cm].
Anthropometric assessments
Anthropometric measurements (total body mass, estimated fat-free mass, and estimated percentage
body fat) were determined before and after the 8-week training period (Table 1). Skinfold
measurements were obtained from three sites (anterior thigh, axillary fold, and abdomen) prior to
extraction of the muscle biopsy samples and were used in the equation proposed by Jackson and
Pollock (1978) for body composition analyses (e.g., estimation of percentage body fat).
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Table 1. Total body mass and estimated percentage body fat. Values given are mean (SD). (LOW REP
Low repetition group, INT REP intermediate repetition group, HIGH REP high repetition group, Pre
pre-training, Post post-training)
Training condition Body mass (kg) % Body fat
CONTROL
Pre 80.8 (23.3) 14.6 (6.6)
Post 81.4 (24.3) 14.0 (6.5)
LOW REP
Pre 80.1 (8.4) 13.9 (3.7)
Post 82.4 (8.3) 14.3 (4.0)
INT REP
Pre 79.5 (7.8) 14.7 (4.8)
Post 81.2 (8.3) 16.0 (5.3)
HIGH REP
Pre 70.2 (9.5) 11.2 (3.9)
Post 71.5 (9.2) 11.4 (3.7)
Maximal oxygen consumption
A previous study from this laboratory (Hagerman et al. 2000) demonstrated significant improvements
in maximum oxygen consumption (
O
2max
) and time to exhaustion following 16 weeks of
resistance training in elderly men. Therefore, aerobic capacities were determined for all subjects at the
beginning and end of the study. Testing was administered on a Monark cycle ergometer using a graded
protocol that increased the intensity at regular intervals. The subjects began pedaling at a frequency of
60 rpm at 60 W. Every minute the workload was progressively increased by 30 W. Termination of the
test occurred when the subject could no longer maintain the required power or stopped voluntarily due
to exhaustion. A test was considered valid if one of the following criteria was observed: (1) predicted
maximal heart rate was attained, (2) oxygen consumption (
O
2
) leveled off or declined, or (3) a
respiratory exchange ratio (R) of greater than 1.1 was reached (see Howley et al. 1995).
O
2
was
measured every 20 s. Heart rate and rate of perceived exertion were measured at each exercise
intensity.
O
2max
, pulmonary ventilation (
E
), expired carbon dioxide, and R were measured
using semiautomated-computerized open-circuit spirometry (Vacumed, Ventura, Calif., USA) that
included a Parkinson-Cowan dry gas meter, and carbon dioxide infrared and oxygen paramagnetic gas
analyzers. Heart rate was monitored every minute using Polar CIC transmitters and receivers. Time to
exhaustion was recorded as a multiple of 20 s from the initiation of the test. Immediately following the
cycle test, the subjects were seated for a 5-min recovery period before a blood sample was obtained for
analysis of whole-blood lactate.
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Maximal strength and muscular endurance tests
All subjects (including the controls) participated in a 1-week orientation program for familiarization
with the equipment and exercises (Dudley et al. 1991). Proper lifting technique was demonstrated and
practiced for each of the three lower-limb exercises (leg press, squat, and knee extension). Both
maximal dynamic strength (1RM) and local muscular endurance (maximum number of repetitions
performed with 60% of 1RM) were assessed for each of the exercises at the beginning and end of the
study. Because of the exhaustive nature of the endurance test, the maximal strength test was always
performed first. After warming up, the load was set at 90% of the predicted 1RM, and was increased
after each successful lift until failure (Staron et al. 1990). Periods of rest (approximately 4-5 min) were
allotted between each attempt to ensure recovery. A test was considered valid if the subject used
proper form and completed the entire lift in a controlled manner without assistance. Once the 1RM
was determined, 60% of this value was calculated for the local muscular endurance test. After a
sufficient recovery period (
4-5 min), the subjects performed as many repetitions as possible with
60% of 1RM until failure.
Strength-training protocols
The training subjects participated in an 8-week high-intensity training program for the lower
extremities. Workouts were performed 2 days/week for the first 4 weeks and 3 days/week for the final
4 weeks. The training subjects used one of three different regimens. The training programs were
adapted from several previous studies (Anderson and Kearney 1982; Jackson et al. 1990; Stone and
Coulter 1994), and were designed to be approximately equal in volume
(resistance repetitions sets) with the rest periods between sets and exercises adjusted according to
the strength-endurance continuum (Fleck and Kraemer 1997). Therefore, those individuals working on
the endurance end of the continuum performed fewer sets and had shorter rest periods compared with
the other training groups. The exercises were performed in the fixed order of leg press, squat, and knee
extension. After warming up, the Low Rep group performed 3-5 repetitions maximum (3-5 RM) for
four sets with 3 min rest between sets and exercises, the Int Rep group performed 9-11 RM for three
sets with 2 min rest, and the High Rep group performed 20-28 RM for two sets with 1 min rest. During
the study, the resistance was progressively increased to maintain these ranges of repetitions per set.
For each set, the training subjects performed repetitions until failure. If the subject performed
repetitions beyond the prescribed training zone, the weight was sufficiently increased to bring the
number of repetitions back within the RM training zone. All subjects were supervised and verbally
encouraged during each set. Maximal heart rates were measured during training in weeks 2 and 7 to
compare the cardiorespiratory stress of each group’s workout. Training heart rates were calculated as a
percentage of the maximal heart rate obtained during the and cycle ergometer
O
2max
pre- and
post-training tests. Values from week 2 were calculated as a percentage of the maximal heart rate
obtained from the pre-training maximal test and those from week 7 as a percentage of the post-training
maximal test. Workouts began and ended with 10-15 min of calisthenics, stretching, and low-intensity
cycling.
Muscle biopsy sampling
Muscle biopsy samples (80-160 mg) were extracted from the superficial region (depth of 3-4 cm) of
the vastus lateralis muscle (approximately mid-shaft) using the percutaneous needle biopsy technique
(Bergström 1962). The muscle samples were removed from the needle, oriented in tragacanth gum,
immediately frozen in isopentane cooled by liquid nitrogen to -159°C, and stored at -74°C until further
- 5 -
analyses could be performed. Biopsy samples were obtained at the beginning and end of the study.
Because of possible variations in fiber-type distribution from superficial to deep and proximal to distal
(Blomstrand and Ekblom 1982), attempts were made to extract pre-training and post-training tissue
samples from within a small area of the muscle using the pre-biopsy scar and depth markings on the
needle. As such, successive incisions were made approximately 0.5 cm apart. The pre-training and
post-training biopsy sites were far enough apart so that the insertion of the first biopsy needle and
extraction of tissue did not affect the area of the second biopsy. To ensure adequate sample sizes, large
biopsy specimens were obtained using a double-chop method (Staron et al. 1990, 1991, 1994)
combined with suction (Evans et al. 1982).
Fiber-type and cross-sectional area determinations
The frozen biopsy specimens were thawed to -24°C and sectioned serially (12 µm thick) for
histochemical analysis. To determine the muscle fiber-type composition, myofibrillar adenosine
triphosphatase (mATPase) histochemistry was performed using preincubation pH values of 4.3, 4.6,
and 10.4 (Guth and Samaha 1969; Brooke and Kaiser 1970). Six fiber types (I, IC, IIC, IIA, IIAB, and
IIB) were distinguished based on their staining intensities (Fig. 1a-c). Fiber types IIAB and IIB have
more recently been referred to as IIAX and IIX, respectively (Smerdu et al. 1994; Ennion et al. 1995).
Cross sections of pre-training and post-training biopsy specimens from an individual were placed on
the same glass coverslip so that they could be assayed simultaneously for mATPase activity. A
composite photomontage of each mATPase preparation after preincubation at pH 4.6 was made using
Polaroid micrographs (
56 magnification). These were used in combination with the other mATPase
preparations to determine fiber-type percentages and total fiber number in each biopsy sample.
Cross-sectional area was determined on at least 50 fibers per major fiber type (I, IIA, and IIB) per
biopsy sample using the NIH imaging software program (version 1.55).
- 6 -
Fig. 1. Serial cross sections of muscle samples taken from a control subject demonstrating fiber-type
delineation using myofibrillar adenosine triphosphatase histochemistry after preincubation at pH 10.4
(a), 4.3 (b), and 4.6 (c), and capillary supply using Ulex europaeus agglutinin lectin histochemistry
(d). Arrows in d indicate capillaries. (I Type I muscle fiber, IC type IC muscle fiber, IIC type IIC
muscle fiber, A type IIA muscle fiber, AB type IIAB muscle fiber, B type IIB muscle fiber).
Bar=100 µm
- 7 -
Myosin heavy chain (MHC) analysis
MHC analyses were performed on the biopsy samples using sodium dodecylsulfate
(SDS)-polyacrylamide electrophoretic techniques (Fig. 2). The protocol for analyzing the specimens
was based on procedures of Perrie and Bumford (1986) with modifications used for single-fiber
analysis (Staron 1991; Staron and Hikida 1992). Briefly, four to six serial cross sections (20 µm thick)
from each biopsy sample were placed into 0.5 ml of a lysing buffer containing 10% (wt/vol) glycerol,
5% (vol/vol) 2-mercaptoethanol, and 2.3% (wt/vol) SDS in 62.5 mM tris (hydroxymethyl)
aminomethane HCl buffer (pH 6.8) and heated for 10 min at 60°C. Small amounts of the extracts
(3-5 µl) were loaded on 4-8% gradient SDS-polyacrylamide gels with 4% stacking gels (Bär and Pette
1988), run overnight (19-21 h) at 120 V, and stained with Coomassie Blue. MHC isoforms were
identified according to their apparent molecular masses compared with those of marker proteins and
migration patterns from single-fiber analyses. Relative MHC isoform content was subsequently
determined using a laser densitometer.
- 8 -
Fig. 2. Myosin heavy chain (MHC) analysis of muscle biopsy samples obtained from a representative
subject in each of the four groups (C control, low low repetition, int intermediate repetition, high high
repetition) at the beginning (pre) and end (post) of the study. Note the decrease in the band
corresponding to MHCIIb from pre to post for the training subjects. (MHCIIb Myosin heavy chain IIb,
MHCIIa myosin heavy chain IIa, MHCI myosin heavy chain I)
Capillary assessment
Capillaries were identified on cross sections serial to those used for fiber-type determination by Ulex
europaeus agglutinin I (UEA-I) lectin histochemistry, according to the procedure of Holthöfer et al.
(1982) (Fig. 1d). UEA-I is a sensitive and reliable marker for endothelium. Capillary data were
collected from at least 50 fibers per major fiber type (I, IIA, IIB) per biopsy sample. Fibers that lay on
the border of a muscle fascicle were not included in the analysis. Also, capillaries on the edge of a
sampling area were added together and divided by two to correct for fiber sharing, according to Plyley
and Groom (1975). Several measures of muscle capillarity were used in the present investigation. The
number of capillaries per unit area (capillary density, CD=capillaries/mm
2
) was measured to give an
indication of the number of capillaries present in a standard area. The number of capillaries per fiber
(CF) was measured as a global representation of capillary supply, whereas the number of capillaries
per fiber-type area (CFTA) was determined to assess relative differences in capillary supply to
individual fiber types. Finally, the number of capillaries per fiber type (CFT) was reported to
demonstrate an absolute measure of capillary supply to each fiber type.
Statistical analysis
Descriptive statistics were used to derive means and standard deviations (SD) for all variables, and
data are presented in the form mean (SD). Statistical analyses for each dependent variable were
accomplished using a separate two-way analysis of variance (ANOVA) with repeated measures (3
2
design: 3 groups by 2 time points). When a significant F value was achieved, post-hoc comparisons
were accomplished via a Fisher’s least significant differences (LSD) test. Using the nQuery Advisor
software (Statistical Solutions, Saugus, Mass., USA), the statistical power for the n size used ranged
from 0.76 to 0.87. Differences were considered significant at P=0.05.
- 9 -
Results
Anthropometric data
No significant differences were detected either between or within any of the groups for the
anthropometric measurements (Table 1).
Cardiorespiratory measurements
O
2max
,
E
, time to exhaustion, and aerobic power were monitored at the beginning and end of
the study (Table 2). All subjects completed valid
O
2max
tests (see Methods). The average maximal
heart rates were 188.2 (16.1) and 189 (9.6) beats/min for the pre- and post-training tests, respectively.
Lactate measurements did not differ between the groups, and averaged 12.4 (1.7) and 11.6
(2.5) mmol/l for the pre- and post-training tests, respectively.
O
2max
and
E
were unchanged at
the end of the study for all training groups. The High Rep group was the only training group to show a
significant increase in both time to exhaustion [from 7.6 (1.8) to 9.1 (1.3) min] and maximal aerobic
power [from 265 (47) to 308 (41) W] in the cycle endurance test. As expected, the Con group
demonstrated no significant changes for the various cardiorespiratory parameters with the exception of
a significant decrease in
E
at the end of the study (Table 2).
Table 2. Cardiorespiratory data obtained from pre- and post-training endurance tests. Values given are
mean (SD). (
O
2
Oxygen consumption, O
2max
maximum oxygen consumption,
E
minute
ventilation, Max power maximal aerobic power, t time to exhaustion)
Training
condition
O
2max
(ml/kg/min)
O
2
(l/min)
E
(l/min)
Max power
(W)
t (min)
CONTROL
Pre 48.7 (9.6) 3.81 (0.77) 152.0 (28.5) 276 (58) 8.5 (1.8)
Post 44.8 (7.6) 3.32 (0.70)
123.6
(38.6)*
276 (39) 8.4 (1.6)
LOW REP
Pre 50.3 (5.6) 4.00 (0.45) 140.1 (22.9) 297 (41) 8.9 (1.3)
Post 48.5 (6.6) 3.97 (0.46) 132.1 (25.6) 307 (36) 9.2 (1.2)
INT REP
Pre 48.1 (3.7) 3.88 (0.41) 149.8 (17.2) 290 (34) 9.0 (1.0)
Post 45.7 (4.4) 3.76 (0.45) 137.8 (25.2) 293 (33) 9.0 (1.2)
HIGH REP
Pre 51.0 (10.4) 3.52 (0.55) 140.3 (33.5) 266 (47) 7.6 (1.8)
Post 52.5 (5.7) 3.74 (0.50) 153.7 (21.7) 309 (41)*
9.1
(1.3)*
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*Significantly different from corresponding pre-training value
Workout volume and cardiorespiratory stress
The average volume of total work accomplished (resistance repetitions sets) was calculated for
each training group every week. No significant differences in volume were found between the training
groups. Volumes had a tendency to rise slightly for all three training groups for each exercise
throughout the duration of the training period. However, no significant differences in volume occurred
over time. Likewise, no differences between the groups were found when comparing heart rates
obtained during training in weeks 2 and 7. The average training heart rates for week 2 were 87%, 86%,
and 93%, and for week 7 were 88%, 87%, and 91% for the Low Rep, Int Rep, and High Rep groups,
respectively.
Maximal dynamic strength and muscular endurance
All three training groups showed significant increases in maximal dynamic strength (1RM) for all
three exercises compared to their pre-training values (Fig. 3). Although not shown, this was also true
for maximal dynamic strength relative to total and lean body mass. No significant changes in 1RM
were demonstrated pre- to post-training for the Con group (Fig. 3). In a comparison between groups,
the relative and absolute increases in maximal dynamic strength for the leg press and squat exercises
were significantly greater for Low Rep compared to the other groups (Fig. 3). For the leg extension,
the post-training 1RM value for the Low Rep group was significantly greater than for both the High
Rep and Con groups (Fig. 3).
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Fig. 3. Bar graphs comparing maximal strength (1-repetition maximum, 1RM) values [mean (SD)] for
the three lower-limb exercises pre- (
) and post-training ( ). (C Control group, Low Rep low
repetition group, Int Rep intermediate repetition group, High Rep high repetition group). *Significantly
greater than corresponding pre-training value;
significantly greater than all corresponding
post-training values;
#
significantly greater than corresponding High, Rep and Control post-training
values;
+
significantly greater than corresponding Control post-training values
- 12 -
Compared to the results obtained for maximal dynamic strength, the reverse was true for the
assessment of local muscular endurance. High Rep performed significantly more repetitions using
60% 1RM after training for all three exercises, and these post-training values were greater than all
other corresponding group values (Fig. 4). Although all three training groups significantly increased
the number of repetitions using 60% of the 1RM in the squat exercise after training, neither the Int Rep
nor Low Rep groups demonstrated a significant improvement at 60% 1RM after training for the leg
press or leg extension (Fig. 4). Indeed, the Low Rep group performed significantly fewer repetitions
for the leg press after training (Fig. 4). No significant changes in local muscular endurance were found
for the Con group (Fig. 4).
- 13 -
Fig. 4. Bar graphs comparing the maximal number of repetitions using 60% 1RM [mean (SD)] for the
three lower-limb exercises pre- (
) and post-training ( ). *Significantly different from
corresponding pre-training value;
significantly greater than all corresponding post-training values;
significantly greater than Low, Rep and Control corresponding post-training values;
+
significantly
greater than corresponding Control post-training values
- 14 -
Fiber-type distribution and MHC content
For all three training groups, the percentage of type IIB fibers decreased, with a concomitant increase
in the percentage of fibers classified as type IIAB (Table 3). No changes in fiber-type distribution were
found for the Con group. These data were supported by the changes in the relative percentages of
MHC isoforms. The biopsy specimens from all three training groups showed a significant decrease in
MHCIIb and a concomitant increase in MHCIIa (Fig. 2, Table 4). No change was found in MHC
content for the Con group.
Table 3. Muscle fiber type percentages determined using myofibrillar adenosine triphosphatase
histochemical methods. Values given are mean (SD). (n Mean number of fibers per biopsy sample)
Training condition Muscle fiber type
I IC IIC IIA IIAB IIB n
CONTROL
Pre 35.6 (11.3) 1.0 (1.7) 0.7 (1.2) 28.2 (10.3) 4.6 (2.6) 29.9 (5.6) 1040 (451)
Post 39.9 (9.6) 1.4 (1.9) 0.6 (0.5) 31.2 (10.3) 3.2 (0.9) 23.7 (2.8) 1100 (452)
LOW REP
Pre 38.3 (10.9) 0.3 (0.6) 0.6 (0.9) 33.3 (7.3) 5.4 (2.1) 22.1 (9.0) 1022 (255)
Post 42.8 (11.3) 1.6 (1.6) 3.9 (3.3) 31.0 (11.7) 12.1 (7.0)* 8.6 (6.1)* 912 (542)
INT REP
Pre 38.6 (9.3) 0.5 (0.6) 0.5 (0.8) 33.1 (7.7) 6.1 (4.1) 21.2 (9.0) 953 (463)
Post 40.7 (9.9) 1.8 (2.1) 1.6 (1.3) 34.1 (11.8) 11.3 (2.8)* 10.5 (9.8)* 885 (471)
HIGH REP
Pre 34.9 (13.3) 0.7 (1.1) 2.4 (4.8) 28.5 (10.5) 5.8 (5.1) 27.7 (15.8) 1110 (561)
Post 40.4 (6.0) 1.8 (3.6) 3.0 (2.8) 32.2 (9.5) 12.0 (6.1)* 10.6 (5.8)* 1342 (549)
*Significantly different from corresponding pre-training value
Table 4. Relative myosin heavy chain isoform percentages from homogenate muscle samples
determined using sodium dodecylsulfate-polyacrylamide gel electrophoresis. Values given are mean
(SD). (MHCI Myosin heavy chain I, MHCIIa myosin heavy chain IIa, MHCIIb myosin heavy chain
IIb)
- 15 -
Training condition MHCI MHCIIa MHCIIb
CONTROL
Pre 34.4 (14.0) 41.4 (11.1) 23.2 (4.9)
Post 36.9 (12.0) 40.7 (8.7) 22.4 (5.0)
LOW REP
Pre 32.8 (8.2) 44.6 (6.7) 22.6 (5.6)
Post 35.3 (11.3) 55.4 (9.3)* 9.3 (2.9)*
INT REP
Pre 28.6 (7.9) 47.1 (6.9) 24.3 (8.4)
Post 31.6 (8.0) 57.6 (6.6)* 10.8 (3.7)*
HIGH REP
Pre 30.1 (10.2) 42.4 (4.7) 27.5 (11.6)
Post 33.2 (6.3) 53.9 (5.3)* 12.9 (3.5)*
*Significantly different from pre-training values
Cross-sectional area
A hypertrophic effect was observed after resistance training for only the Int Rep and Low Rep groups
(Table 5). For these two training groups, the cross-sectional areas of all three major fiber types (I, IIA,
and IIB) were significantly larger after training. The 8-week progressive resistance training program
caused the cross-sectional areas of the major fiber types to increase by approximately 12.5% for type I,
19.5% for type IIA, and 26% for type IIB, for both the Int and Low Rep groups. No significant area
changes were found for the High Rep and Con groups (Table 5). However, there was a tendency for
the type IIB cross-sectional area to increase after training for the High Rep group (P=0.13).
Table 5. Cross-sectional area (µm
2
) of the three major muscle fiber types. Data are presented as mean
(SD)
- 16 -
Training condition Muscle fiber type
I IIA IIB
CONTROL
Pre 5208 (1494) 6070 (1944) 4648 (1043)
Post 5155 (1239) 5982 (1547) 4813 (672)
LOW REP
Pre 4869 (1178) 5615 (1042) 4926 (942)
Post 5475 (1425)* 6903 (1442)* 6171 (1436)*
INT REP
Pre 4155 (893) 5238 (787) 4556 (877)
Post 4701 (809)* 6090 (1421)* 5798 (1899)*
HIGH REP
Pre 3894 (1085) 5217 (1009) 4564 (1179)
Post 4297 (1203) 5633 (596) 5181 (714)
*Significantly different from corresponding pre-training values
Capillarization
Comparing pre- to post-training values for all groups, no significant differences were found in either
CD or CF (Table 6). Likewise, no significant changes occurred in CFTA for any group (data not
shown). With the exception of a significant increase after training for CFT for type IIA for the Int Rep
group, no significant changes occurred in CFT for any of the three types (I, IIA, or IIB; Table 6).
Table 6. Muscle capillary supply as determined using Ulex europaeus agglutinin I lectin
histochemistry. Values given are mean (SD). (n caps/I Number of capillaries per type I fiber, n
caps/IIA number of capillaries per type IIA fiber, n caps/IIAB number of capillaries per type IIAB
fiber, n caps/IIB number of capillaries per type IIB fiber, n caps/fiber number of capillaries per fiber, n
caps/mm
2
number of capillaries per millimeter squared)
- 17 -
Training condition n caps/I n caps/IIA n caps/IIAB n caps/IIB n caps/fiber
n caps/mm
2
CONTROL (n=5)
Pre 4.1 (0.3) 3.9 (0.6) 3.6 (0.5) 3.2 (0.5) 1.7 (0.6) 268 (89)
Post 4.7 (0.6) 4.3 (0.3) 4.4 (1.0) 3.6 (0.9) 1.6 (0.3) 273 (29)
LOW REP (n=7)
Pre 4.5 (0.7) 4.7 (0.7) 3.9 (0.9) 3.7 (0.6) 1.6 (0.4) 273 (32)
Post 4.7 (0.8) 4.8 (0.7) 4.2 (1.1) 4.5 (1.0) 1.7 (0.4) 251 (39)
INT REP (n=6)
Pre 3.7 (0.4) 3.7 (0.4) 3.5 (0.5) 3.2 (0.4) 1.2 (0.2) 244 (50)
Post 4.4 (0.5) 4.7 (0.5)* 4.5 (0.8) 4.1 (0.4) 1.5 (0.2) 254 (39)
HIGH REP (n=5)
Pre 3.7 (0.3) 3.8 (0.7) 3.7 (0.3) 3.6 (0.7) 1.3 (0.1) 263 (44)
Post 4.1 (0.4) 4.7 (0.7) 4.7 (0.6) 3.9 (0.2) 1.5 (0.3) 282 (34)
*Significantly different from corresponding pre-training value
Discussion
Strength adaptations
Although a few resistance-training studies have challenged DeLorme’s (1945) theory of a
strength-endurance continuum (DeLateur et al. 1968; Clark and Stull 1970; Stull and Clark 1970),
most research in this area supports the idea of task specificity related to specific set/repetition
combinations (e.g., Stull and Clark 1970; Anderson and Kearney 1982). The results from the present
investigation support the findings of these earlier studies on strength adaptations. Although maximal
dynamic strength significantly improved for all three training groups, the Low Rep group improved
the most. For example, maximal dynamic strength improvements in the leg press exercise amounted to
61% for Low Rep compared to 36% for Int Rep, 32% for High Rep, and 6% for Con (Fig. 3). On the
other hand, local muscular endurance in the leg press improved the most for High Rep compared to the
other groups: 94% improvement for High Rep, 10% for Int Rep, -20% for Low Rep, and -19% for Con
(Fig. 4).
Cardiorespiratory adaptations
Although traditional resistance training involves heavy resistance combined with low numbers of
repetitions, low resistance/high repetition regimens must still be regarded as a form of resistance
training. Even working on the "extreme" endurance end of the strength-endurance continuum
(performing as many as 150 repetitions) usually means performing submaximal repeated contractions
for less than 5 minutes/set (e.g., Stull and Clark 1970; Anderson and Kearney 1982). However,
improvements in short-term endurance following a resistance-training program have been reported.
After 10 weeks of a heavy-resistance-training program, Hickson et al. (1980) found a significant
increase in time to exhaustion for both cycling and running with no significant changes in
O
2max
.
Likewise, Marcinik et al. (1991) reported that 12 weeks of circuit strength training improved cycle
- 18 -
endurance performance independent of changes in O
2max
. Similar findings have also been reported
when resistance training is added to an aerobic endurance-training program in young individuals
(Hickson et al. 1988; Paavolainen et al. 1999), as well as in elderly men (Grimby et al. 1992) and
women (Ferketich et al. 1998). Results from the present study support these findings. The High Rep
group significantly improved their cycling performance (both maximal aerobic power and time to
exhaustion) without changes in
O
2max
(Table 2). Although this may seem to contradict the basic
principles of training specificity, enhanced long-term work capacity also requires muscular strength
and anaerobic power (Tanaka and Swensen 1998). In addition, resistance training has been shown to
improve running economy (Johnston et al. 1995; Paavolainen et al. 1999) and may, thus, also improve
cycling economy. Such improvements in endurance performance following a resistance-training
program may be related to increases in lactate threshold and lower-limb strength (Marcinik et al.
1991), and therefore, may not necessarily be related to increases in aerobic capacity.
Muscle fiber type and cross-sectional area
Although strength and performance adaptations to varied resistance training programs are fairly well
documented, scant information exists regarding specific neuromuscular adaptations. Our hope was to
gain some insight into what may be happening within the muscle (i.e., changes in fiber size, fiber type,
and capillarity) that could potentially contribute to these documented differences in maximal strength,
local muscular endurance, and performance.
Very few studies have attempted to document muscular changes following different modes of
resistance training. Some studies have used indirect methods to measure changes in cross-sectional
area (magnetic resonance imaging and ultrasound scanning) and have reported similar area and
strength adaptations in young men (Chestnut and Docherty 1999), young women (Hisaeda et al. 1996),
and early postmenopausal women (Bemben et al. 2000) subjected to different sets/repetition maximum
training protocols. To our knowledge, only two studies have investigated the effects of different types
of resistance training programs on skeletal muscle utilizing muscle biopsy sampling (Jackson et al.
1990; Taaffe et al. 1996), and neither of these specifically addressed the "strength-endurance
continuum".
Advantages of the present study compared with previous work in this area include a non-exercising
control group, the full range of histochemical fiber types, relative MHC content to validate the
histochemical data, cross-sectional area determined from at least 50 fibers per major type, free weights
for training and testing, and the inclusion of various cardiorespiratory parameters. In addition, in the
present study we chose three different, yet practical, resistance-training protocols to specifically focus
on muscular adaptations at different points along the strength-endurance continuum.
Similar to previous resistance-training studies (see Staron and Johnson 1993), the present study found
exercise-induced fiber-type conversions within the fast fiber population in the direction of type IIB to
IIA. This fiber type transformation occurred to the same extent in all three training groups, amounting
to approximately a two-fold increase in the percentage of fibers classified as type IIAB with a
concomitant decrease in fibers classified as "pure" type IIB. This finding of similar fiber-type
conversions between the three training groups is perhaps not surprising considering previously
published data on both aerobic and anaerobic conditioning in humans (Staron and Johnson 1993). It
appears that any exercise stimulus (e.g., resistance or endurance) that is sufficient in duration and/or
intensity has the potential to ultimately cause conversions within the fast fiber population from type
IIB to type IIA (Staron and Johnson 1993; Kraemer et al. 1995). Although this transformation took
place in the present study following all three training protocols, significant differences between the
groups were noted regarding the extent of exercise-induced hypertrophy.
- 19 -
The logical and often sought after outcome of a resistance-training program is increased size and force
output of the exercised muscles. Hypertrophy appears to be the result of an increased rate of protein
synthesis (Chesley et al. 1992; Phillips et al. 1997), which contributes to an absolute increase in the
amount of contractile elements (MacDougall et al. 1979, 1982; Lüthi et al. 1986). Numerous studies
have demonstrated a hypertrophic response for all three major fiber types (I, IIA, and IIB) following
short-term resistance training in previously untrained young and elderly individuals (e.g., Staron et al.
1990, 1991; Hikida et al. 2000). However, this exercise-induced hypertrophy appears to affect the fast
fibers to a greater extent than the slow, type I fibers (see Tesch 1987). In the present study, the
hypertrophic response was minimized (essentially negated) in those individuals in the High Rep group.
On the contrary, the cross-sectional area of all three major fiber types significantly increased for those
subjects training at the strength end of the continuum (Table 5). Interestingly, the hypertrophic
response was similar between both the Low Rep and Int Rep groups. It has often been accepted that
improved strength/power results from high intensity/low volume training, whereas low intensity/high
volume training maximizes muscle hypertrophy (Hisaeda et al. 1996). Based on data from the present
investigation, this may not be entirely true. Indeed, data from the present investigation suggest low and
intermediate RM training induces similar muscular adaptations, at least after short-term training in
previously untrained subjects.
Capillarity
Results from resistance-training studies investigating capillary changes are equivocal, with reports of
increases, decreases and no changes (e.g., Schantz 1982; Tesch et al. 1984, 1990; Hather et al. 1991;
Wang et al. 1993; McCall et al. 1996; Hagerman et al. 2000). In the present study, there was a
tendency for the number of capillaries per fiber to increase with training, indicating the formation of
new capillaries within the muscle (Table 6). Such findings have been reported previously following
resistance training in humans (Hather et al. 1991; McCall et al. 1996; Hepple et al. 1997; Green et al.
1998), and suggest that capillary changes are proportional to changes in fiber size. In other words,
capillary growth may have been masked by the increase in area occupied by the muscle fibers. As
such, capillary density did not change in the present study, even though a significant amount of
hypertrophy occurred following training for the Low Rep and Int Rep groups.
Although there were no significant differences in either CD or CF after training in the present study,
there was a trend suggesting potential differences between groups. CD went down 8% for Low Rep
and went up 4% for Int Rep and 7% for High Rep. Likewise, there was a tendency for CF to increase a
greater amount post-training for Int Rep and High Rep (23% and 18%, respectively) compared to Low
Rep and Con (4%). Taken together, these data suggest that continued training may have resulted in
significant differences between the groups, lending support to the idea that capillary adaptations occur
on a continuum that is based on the duration and intensity of training. As such, high repetition/light
resistance training appears to cause capillary adaptations more similar to aerobic endurance training
compared to low repetition/heavy resistance training.
In conclusion, all three training regimens caused similar alterations within the fast fiber-type
population (IIB to IIA fiber conversions) and in MHC content. Differences were, however, apparent
between the three training groups in the hypertrophic response, and for various cardiorespiratory
parameters. These specific post-training adaptations obviously contributed to the differences found
between the groups for maximal dynamic strength and local muscular endurance. Those individuals
training with heavier loads improved the most in maximal strength, whereas those who trained with
the lighter loads improved the most using 60% of 1RM. Interestingly, both groups working on the
strength end of the strength-endurance continuum (Low Rep and Int Rep) had a similar hypertrophic
response. It has often been accepted that gains in strength/power result from high intensity/low volume
training, whereas low intensity/high volume training maximizes muscle hypertrophy (Hisaeda et al.
- 20 -
1996). Based on data from the present investigation, low and intermediate RM training appears to
induce similar muscular adaptations, at least after short-term training in previously untrained subjects.
Overall, however, data from the current investigation demonstrate that both physical performance and
the associated physiological adaptations are linked to the intensity and number of repetitions
performed.
Acknowledgements. The authors wish to thank the Ohio University College of Osteopathic Medicine
Photographic and Graphic Departments for help with the figures and tables. We are also grateful to
those individuals who assisted in supervising the training and especially to the subjects who
volunteered and participated. Portions of this work were supported by the O.U. College of Osteopathic
Medicine and the Office of Research. G.E.R. Campos was supported by FAPESP, 95/4744-4, São
Paulo, Brazil.
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... In general, strength training has guidelines such as intensity, frequency, shape, set, and number of repetitions of exercise [2]. In traditional training, exercise with a load of more than 65% of 1 RM can be expected, but in blood flow restriction training programs, a 20 to 50% level of 1 RM is maintained, and 1 set is performed between 25 and 30 times [4]. In the case of this training, the upper and lower body should be recessed for 15 s and 30 s, respectively. ...
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Regular physical activity and exercise can improve your health and reduce your risk of developing various diseases including type 2 diabetes, cardiovascular disease, and cancer. Physical activity and exercise can have numerous immediate and chronic health benefits, such as managing weight, blood cholesterol level, blood pressure, and muscles [1]. Most importantly, regular physical activity and exercise can offer a better quality of life (e.g., more energy, a better mood, feeling more relaxed, and sleeping better). The American College of Sports Medicine (ACSM) provides recommendations and guidelines for physical activity and exercise that all healthy adults aged 18–65 years should participate in moderate-intensity aerobic activity for a minimum of 30 min five days per week or vigorous-intensity aerobic activity for a minimum of 20 min three days per week. In addition, adults should maintain or increase muscular strength and endurance for a minimum of two days per week (ACSM’s Guidelines for Exercise Testing and Prescription) [2]. Taken together, both aerobic and strength activities are important for optimal physical fitness. While practical concerns such as busy schedules and poor health can make exercise more challenging, for most of us, the biggest barriers are mental. Maybe it is a lack of confidence that keeps us from taking positive steps, or it is that the motivation easily burns out, or that we are too quickly discouraged and give up. Therefore, new exercise methods that enable exercise to be sustainable for managing health are essential. Among the many new exercise trends, we would like to briefly introduce some of the exercise modalities including blood flow restriction, electromyostimulation, hypoxic training, vibration, and interval training.
... Exercise training can induce specific muscular adaptations depending on the exercise mode (Hawley, 2009;Hawley et al., 2014;Coffey and Hawley, 2016). For instance, resistance exercise training interventions maximize neuromuscular adaptations, such as muscle hypertrophy and strength (Campos et al., 2002;Mitchell et al., 2013;Bellamy et al., 2014;Nader et al., 2014;Damas et al., 2016;Morton et al., 2019). On the other hand, aerobic exercise training interventions improve aerobic muscle metabolism and cardiorespiratory fitness (e.g., aerobic power) (Maeda et al., 2001;Coffey and Hawley, 2007;Daussin et al., 2007;Sloth et al., 2013;Konopka et al., 2014;Milanovic et al., 2015). ...
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Losses in skeletal muscle mass, strength, and metabolic function are harmful in the pathophysiology of serious diseases, including breast cancer. Physical exercise training is an effective non-pharmacological strategy to improve health and quality of life in patients with breast cancer, mainly through positive effects on skeletal muscle mass, strength, and metabolic function. Emerging evidence has also highlighted the potential of exercise-induced crosstalk between skeletal muscle and cancer cells as one of the mechanisms controlling breast cancer progression. This intercellular communication seems to be mediated by a group of skeletal muscle molecules released in the bloodstream known as myokines. Among the myokines, exercise-induced circulating microRNAs (c-miRNAs) are deemed to mediate the antitumoral effects produced by exercise training through the control of key cellular processes, such as proliferation, metabolism, and signal transduction. However, there are still many open questions regarding the molecular basis of the exercise-induced effects on c-miRNA on human breast cancer cells. Here, we present evidence regarding the effect of exercise training on c-miRNA expression in breast cancer, along with the current gaps in the literature and future perspectives.
... Modelling the relationship between exercise intensity and the maximum amount of realisable physical work has been an increasingly addressed objective in sports science (Bergstrom, Dinyer, Succi, Voskuil, & Housh, 2021). In resistance training, this relationship has previously been characterised by the term "strength-endurance continuum" (Campos et al., 2002) and can be described for a given exercise by modelling the external load as a function of the number of repetitions performed to momentary failure (RTF) (e.g. Reynolds, Gordon, & Robergs, 2006;Mayhew, Ball, Arnold, & Bowen, 1992). ...
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Purpose: To identify the relationship between load and the number of repetitions performed to momentary failure in the pin press exercise, the present study compared different statistical model types and structures using a Bayesian approach. Methods: Thirty resistance-trained men and women were tested on two separate occasions. During the first visit, participants underwent assessment of their one-repetition maximum (1-RM) in the pin press exercise. On the second visit, they performed sets to momentary failure at 90%, 80% and 70% of their 1-RM in a fixed order during a single session. The relationship between relative load and repetitions performed to failure was fitted using linear regression, exponential regression and the critical load model. Each model was fitted according to the Bayesian framework in two ways: using an across-subjects pooled data structure and using a multilevel structure. Models were compared based on the variance explained (R²) and leave-one-out cross-validation information criterion (LOOIC). Results: Multilevel models, which incorporate higher-level commonalities into individual relationships, demonstrated a substantially better fit (R²: 0.97-0.98) and better predictive accuracy compared to generalized pooled-data models (R²: 0.89-0.93). The multilevel 2-parameter exponential regression emerged as the best representation of data in terms of model fit, predictive accuracy and model simplicity. Conclusion: The relationship between load and repetitions performed to failure follows an individually expressed exponential trend in the pin press exercise. To accurately predict the load that is associated with a certain repetition maximum, the relationship should therefore be modeled on a subject-specific level.
... In this regard, Pareja-Blanco et al. [38] found that an RT program based on 40% VL reduced the percentage of IIX fiber type by almost half. Similarly, other investigations revealed that training to muscle failure would promote IIX to IIA fiber transition [49][50][51][52]. Although more research including molecular mechanisms is needed, a recent study found that incurring high intra-set fatigue (40% VL) throughout an RT program increased the Thr 287 -CaMKII δ D phosphorylation levels, which in turn was negatively associated (r = −0.72, ...
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This study aimed to systematically review the effects of the different velocity loss (VL) thresholds during resistance training (RT) on strength and athletic adaptations. The VL was analyzed as both a categorical and continuous variable. For the categorical analysis, individual VL thresholds were divided into Low-ModVL (≤25% VL) or Mod-HighVL (>25% VL). The efficacy of these VL thresholds was examined using between-group (Low-ModVL vs. Mod-HighVL) and within-group (pre–post effects in each group) analyses. For the continuous analysis, the relationship (R2) between each individual VL threshold and its respective effect size (ES) in each outcome was examined. Ten studies (308 resistance-trained young men) were finally included. The Low-ModVL group trained using a significantly (p ≤ 0.001) lower VL (16.1 ± 6.2 vs. 39.8 ± 9.0%) and volume (212.0 ± 102.3 vs. 384.0 ± 95.0 repetitions) compared with Mod-HighVL. Between-group analyses yielded higher efficacy of Low-ModVL over Mod-HighVL to increase performance against low (ES = 0.31, p = 0.01) and moderate/high loads (ES = 0.21, p = 0.07). Within-group analyses revealed superior effects after training using Low-ModVL thresholds in all strength (Low-ModVL, ES = 0.79–2.39 vs. Mod-HighVL, ES = 0.59–1.91) and athletic (Low-ModVL, ES = 0.35–0.59 vs. Mod-HighVL, ES = 0.05–0.36) parameters. Relationship analyses showed that the adaptations produced decreased as the VL threshold increased, especially for the low loads (R2 = 0.73, p = 0.01), local endurance (R2 = 0.93, p = 0.04), and sprint ability (R2 = 0.61, p = 0.06). These findings prove that low–moderate levels of intra-set fatigue (≤25% VL) are more effective and efficient stimuli than moderate–high levels (>25% VL) to promote strength and athletic adaptations.
... In strength training, particular importance is attributed to the eccentric phase of the movement, which is characterized by a relatively low energy cost, but a very high mechanical stimulus compared to the concentric part of the movement [240,241,361,[395][396][397]. Exercise intensities below 60% of 1 RM are too low to produce adaptations in the active or passive musculoskeletal system [91,398,399]. In sports with high strength requirements, even intensities below 80% of the 1 RM are probably no longer sufficient in the long term to trigger further adaptive processes [122,[400][401][402][403]. The requirement for a high-load volume can be explained on the one hand by the fact that the extent of intentional tissue damage increases with the performance of several sets for the muscles in training, and on the other hand, by the fact that adaptations in the passive musculoskeletal system, in particular, depend on the load volume, in combination with a sufficiently high-load intensity [86,90,91,[404][405][406][407]. ...
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This narrative review deals with the topic of strength training in swimming, which has been a controversial issue for decades. It is not only about the importance for the performance at start, turn and swim speed, but also about the question of how to design a strength training program. Different approaches are discussed in the literature, with two aspects in the foreground. On the one hand is the discussion about the optimal intensity in strength training and, on the other hand, is the question of how specific strength training should be designed. In addition to a summary of the current state of research regarding the importance of strength training for swimming, the article shows which physiological adaptations should be achieved in order to be able to increase performance in the long term. Furthermore, an attempt is made to explain why some training contents seem to be rather unsuitable when it comes to increasing strength as a basis for higher performance in the start, turn and clean swimming. Practical training consequences are then derived from this. Regardless of the athlete’s performance development, preventive aspects should also be onsidered in the discussion. The article provides a critical overview of the abovementioned key issues. The most important points when designing a strength training program for swimming are a sufficiently high-load intensity to increase maximum strength, which in turn is the basis for power, year-round trength training, parallel to swim training and working on the transfer of acquired strength skills in swim training, and not through supposedly specific strength training exercises on land or in the water.
... Depending on the individual's fitness level and training experience, the effectiveness of the required training adaptation is proportional to the resistance training stimulus. In general, the load and intensity of resistance training required to improve muscle strength and achieve skeletal muscle hypertrophy is regarded as 65% or more of the one repetition maximum (1RM) [15,16]. On the other hand, resistance training of less than 65-70% of the 1RM was believed to cause little to no muscle strength gains or skeletal muscle hypertrophy in both young and aged people [17,18] ( Figure 1A). ...
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Resistance training is an extremely beneficial intervention to prevent and treat sarcopenia. In general, traditional high-load resistance training improves skeletal muscle morphology and strength, but this method is impractical and may even reduce arterial compliance by about 20% in aged adults. Thus, the progression of resistance training methods for improving the strength and morphology of muscles without applying a high load is essential. Over the past two decades, various resistance training methods that can improve skeletal muscle mass and muscle function without using high loads have attracted attention, and their training effects, molecular mechanisms, and safety have been reported. The present study focuses on the relationship between exercise load/intensity, training effects, and physiological mechanisms as well as the safety of various types of resistance training that have attracted attention as a measure against sarcopenia. At present, there is much research evidence that blood-flow-restricted low-load resistance training (20–30% of one repetition maximum (1RM)) has been reported as a sarcopenia countermeasure in older adults. Therefore, this training method may be particularly effective in preventing sarcopenia.
... Lindsay and colleagues (2019) proposed that the resistance of oxidative fibers occurs due to the increased expression of utrophin [56], and Selsby and colleagues (2012) observed that overexpression of PGC-1α induces a shift from glycolytic (fast-twitch) to oxidative (slow-twitch) fibers in dystrophic muscles [57]. We know that physical exercise can increase the oxidative capacity of all myofibers, promoting a transition from more glycolytic to more oxidative fibers [58]. This shift has already been observed in different muscles of mdx mice after physical training [24,59,60]. ...
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Duchenne muscular dystrophy (DMD) is a muscle disease characterized by the absence of the protein dystrophin, which causes a loss of sarcolemma integrity, determining recurrent muscle injuries, decrease in muscle function, and progressive degeneration. Currently, there is a need for therapeutic treatments to improve the quality of life of DMD patients. Here, we investigated the effects of a low-intensity aerobic training (37 sessions) on satellite cells, peroxisome proliferator-activated receptor-gamma coactivator (PGC)-1α protein (PGC-1α), and different types of fibers of the psoas muscle from mdx mice (DMD experimental model). Wildtype and mdx mice were randomly divided into sedentary and trained groups (n = 24). Trained animals were subjected to 37 sessions of low-intensity running on a motorized treadmill. Subsequently, the psoas muscle was excised and analyzed by immunofluorescence for dystrophin, satellite cells, myosin heavy chain (MHC), and PGC-1α content. The minimal Feret’s diameters of the fibers were measured, and light microscopy was applied to observe general morphological features of the muscles. The training (37 sessions) improved morphological features in muscles from mdx mice and caused an increase in the number of quiescent/activated satellite cells. It also increased the content of PGC-1α in the mdx group. We concluded that low-intensity aerobic exercise (37 sessions) was able to reverse deleterious changes determined by DMD.
... 10 One of the most common and effective methods for increasing muscle strength and mass is through heavy-load resistance training (HL-RT). 11 The American College of Sports Medicine recommends performing resistance exercise at an intensity greater than 70% of maximum strength in healthy adults in order to achieve muscle adaptations in both size and strength. 12 In the first 12 weeks after ACLR, the use of HL-RT is not feasible, as high levels of musculoskeletal loading may be contraindicated in post-surgical individuals. ...
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Background: Blood flow restriction training (BFRT) has gained popularity in rehabilitation due to its benefits in reducing muscle atrophy and mitigating strength deficits following anterior cruciate ligament reconstruction (ACLR). While the effectiveness and safety of BFRT has been well studied in healthy adult subjects, there is limited information about the use of BFRT in the adolescent population, specifically related to patient tolerance and reported side effects post ACLR. Purpose: To investigate and record reported side effects and patient tolerance to BFRT during ACLR rehabilitation in adolescents. Study design: Prospective Cohort Study. Methods: Patients between 12 and 18 years of age who underwent ACLR at Connecticut Children's were included. Patients utilized an automatic personalized tourniquet system and followed a standardized BFRT exercise protocol over 12 weeks starting 8.72 ± 3.32 days post-op. Upon completion of exercise while using BFRT, patients reported side effects and any adverse events were logged. Descriptive statistics were used to describe the reported side effects and adverse events associated with BFRT and calculate the frequencies of those events over a 12-week period. Results: Five hundred and thirty-five total BFRT sessions were completed between 29 patients (15.39 ± 1.61 years of age). There were zero reports of subcutaneous hemorrhage (SubQ hemorrhage) and deep vein thrombosis (DVT). Reported minor side effects to BFRT included itchiness of the occluded limb (7.85%), lower extremity paresthesia (2.81%), and dizziness (0.75%). A total of 10.47% of BFR treatment sessions were unable to be completed due to tolerance, and 3.5% of sessions required a reduction in limb occlusion pressure (LOP). Conclusion: These preliminary data suggest that BFRT is safe with only minor side effects noted in the adolescent population after ACLR. Further investigations are warranted to continue to evaluate patient tolerance and safety with BFRT, because while these preliminary results suggest a positive safety profile and good tolerance in the adolescent population after ACLR, they represent the experiences of only a small sample. Level of evidence: Level 3.
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New findings: What are the central questions of this study? Do obesity and acute resistance exercise alter the regulation of muscle intercellular communication pathways consistent with inadequate compensatory angiogenesis in response to muscle loading present in individuals with obesity? What is the main finding and its importance? Obesity is associated with differences in both pro- and anti-angiogenic signaling consistent with lower muscle capillarization. Acute resistance exercise increases the release of skeletal muscle small extracellular vesicles independent of body mass. These results identify novel cellular factors associated with impaired angiogenesis in obesity and the positive effects of acute resistance exercise in lean and obese skeletal muscle. Abstract: Introduction Obesity (OB) impairs cell-to-cell communication signaling. Small extracellular vesicles (EVs), which includes exosomes, are released by skeletal muscle and participate in cell-to-cell communications including the regulation of angiogenesis. Resistance exercise (REx) increases muscle fiber size and capillarization. However, while obesity increases muscle fiber size, there is an inadequate increase in capillarization such that capillary density is reduced. It was hypothesized that REx induced angiogenic signaling and EV biogenesis would be lower with obesity. Methods Sedentary lean (LN) and individuals with obesity (OB) (n = 8/group) performed three sets of single leg, knee extension REx at 80% of maximum. Muscle biopsies were obtained at rest, 15 min, and 3 hr post-exercise and analyzed for angiogenic and EV biogenesis mRNA and protein. Results In OB, muscle fiber size was ∼20% greater and capillary density with type II fibers was ∼25% lower compared to LN (p<0.001) . In response to REx, increased vascular endothelial growth factor (VEGF) mRNA (pro-angiogenic) was similar (3-fold) between groups, while thrombospondin-1 (TSP-1) mRNA (anti-angiogenic) increased ∼2.5-fold in OB only (p = 0.010). miR-130a (pro-angiogenic) was ∼1.4-fold (p = 0.011) and miR-503 (anti-angiogenic) was ∼1.8-fold (p = 0.017) greater in OB compared to LN across all time points. In both groups acute REx decreased the EV surface protein Alix ∼50% consistent with the release of exosomes (p = 0.016). Conclusion Acute resistance exercise appears to induce the release of skeletal muscle small EVs independent of body mass. However, with obesity there is predominantly impaired angiogenic signaling consistent with inadequate angiogenesis in response to basal muscle hypertrophy. This article is protected by copyright. All rights reserved.
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La identificación de las respuestas agudas y crónicas inducidas por el ejercicio físico resultan ser las características más recordadas en la fisiología del ejercicio por quienes hemos realizado cursos relacionados a esta área, ya sea como estudiantes de pre o posgrado, lo que está bien si se considera que son los hallazgos más relevantes que debemos reconocer si nos gusta el deporte y, por tanto, lo vivenciamos en primera persona, o realizamos actividad asistencial con deportistas o pacientes. Sin embargo, muchas veces nos olvidamos del marco teórico que sustentan dichos cambios; aspecto crucial, dados los diferentes tipos de actividad física y programas de entrenamiento que se pueden realizar. Esto hace que para algunos se transforme en una verdadera odisea recordar conceptos clásicos, y mas complejo aún poder relacionarlos e integrarlos en el fenómeno que se está evaluando; mientras que para otros se transforma en el pretexto ideal para reencontrarse con libros de ciencias básicas, como aquellos de biología, química, física, bioquímica, fisiología general, análisis del movimiento, etc. Con la finalidad de ayudar a que los contenidos teóricos de fisiología del ejercicio se plasmen en actividades prácticas que se orienten hacia el logro de objetivos de aprendizaje gracias al “aprender haciendo”, incentivando la autorreflexión y el pensamiento crítico, es que se desarrolló el presente manual de actividades prácticas. En este se incorporan las unidades más frecuentes de los programas académicos de universidades e institutos de formación profesional. En cada unidad se presenta el marco teórico que sustenta el tópico principal a tratar, englobando contenidos de diferentes libros y artículos científicos, y finaliza con actividades prácticas a desarrollar en forma personal o en grupos pequeños, tanto en ambientes libres como en el laboratorio, siempre bajo la guía de los académicos responsables de la asignatura. En la creación de este manual participaron académicos de la carrera de Kinesiología UC, aportando a través de su experiencia docente, las mejores actividades en las que se pueda vivenciar lo explicitado previamente en forma teórica. Espero que los contenidos y la forma en que son presentados faciliten el desarrollo de la docencia en el área de la fisiología del ejercicio, tanto a académicos como a estudiantes. De igual manera, los invito a comentar respecto del entendimiento de las actividades prácticas, con la finalidad de incorporar mejoras y potenciar el objetivo principal de la creación de este libro. Por ello, invitamos a los lectores a disfrutar el “aprender haciendo” en fisiología del ejercicio.
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The purpose of this study was to identify and compare the strength, cross-sectional area, specific tension, and anthropometric changes elicited by 4 repetition maximum (RM) and 10RM weight-training protocols in untrained subjects. Twenty-four men (24.17 +/- 1.76 years) volunteered to participate and were randomly assigned to either the 4RM group or the 10RM group. Training was performed 3 times per week for 10 weeks; free weights were used to exercise the forearm extensors and flexors. The 4RM group performed 6 sets of 4 repetitions to failure and the 10RM group performed 3 sets of 10 repetitions to failure. Strength (1RM) was measured at 0, 6, and 10 weeks, and muscle cross-sectional area (determined through magnetic resonance imagery), specific tension (kilograms per square centimeter), and relaxed-and flexed-arm girth (corrected for skinfolds) were measured at 0 and 10 weeks. Significant (p < 0.05) increases in both forearm extensor and flexor 1RM strength, muscle cross-sectional area, specific tension, and flexed-arm girth occurred in both groups. The 4RM and 10RM loading intensities elicited significant and equal increases in strength, cross-sectional area, specific tension, and flexed girth. These results suggest that 4RM and 10RM weight-training protocols equated for volume produce similar neuromuscular adaptations over 10 weeks in previously untrained subjects. (C) 1999 National Strength and Conditioning Association
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To investigate the effects of simultaneous explosive-strength and endurance training on physical performance characteristics, 10 experimental (E) and 8 control (C) endurance athletes trained for 9 wk. The total training volume was kept the same in both groups, but 32% of training in E and 3% in C was replaced by explosive-type strength training. A 5-km time trial (5K), running economy (RE), maximal 20-m speed ( V 20 m ), and 5-jump (5J) tests were measured on a track. Maximal anaerobic (MART) and aerobic treadmill running tests were used to determine maximal velocity in the MART ( V MART ) and maximal oxygen uptake (V˙o 2 max ). The 5K time, RE, and V MART improved ( P < 0.05) in E, but no changes were observed in C. V 20 m and 5J increased in E ( P < 0.01) and decreased in C ( P < 0.05).V˙o 2 max increased in C ( P < 0.05), but no changes were observed in E. In the pooled data, the changes in the 5K velocity during 9 wk of training correlated ( P< 0.05) with the changes in RE [O 2 uptake ( r = −0.54)] and V MART ( r = 0.55). In conclusion, the present simultaneous explosive-strength and endurance training improved the 5K time in well-trained endurance athletes without changes in theirV˙o 2 max . This improvement was due to improved neuromuscular characteristics that were transferred into improved V MART and running economy.
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McCall, G. E., W. C. Byrnes, A. Dickinson, P. M. Pattany, and S. J. Fleck. Muscle fiber hypertrophy, hyperplasia, and capillary density in college men after resistance training. J. Appl. Physiol. 81(5): 2004–2012, 1996.—Twelve male subjects with recreational resistance training backgrounds completed 12 wk of intensified resistance training (3 sessions/wk; 8 exercises/session; 3 sets/exercise; 10 repetitions maximum/set). All major muscle groups were trained, with four exercises emphasizing the forearm flexors. After training, strength (1-repetition maximum preacher curl) increased by 25% ( P < 0.05). Magnetic resonance imaging scans revealed an increase in the biceps brachii muscle cross-sectional area (CSA) (from 11.8 ± 2.7 to 13.3 ± 2.6 cm ² ; n = 8; P < 0.05). Muscle biopsies of the biceps brachii revealed increases ( P < 0.05) in fiber areas for type I (from 4,196 ± 859 to 4,617 ± 1,116 μm ² ; n = 11) and II fibers (from 6,378 ± 1,552 to 7,474 ± 2,017 μm ² ; n = 11). Fiber number estimated from the above measurements did not change after training (293.2 ± 61.5 × 10 ³ pretraining; 297.5 ± 69.5 × 10 ³ posttraining; n = 8). However, the magnitude of muscle fiber hypertrophy may influence this response because those subjects with less relative muscle fiber hypertrophy, but similar increases in muscle CSA, showed evidence of an increase in fiber number. Capillaries per fiber increased significantly ( P < 0.05) for both type I (from 4.9 ± 0.6 to 5.5 ± 0.7; n = 10) and II fibers (from 5.1 ± 0.8 to 6.2 ± 0.7; n = 10). No changes occurred in capillaries per fiber area or muscle area. In conclusion, resistance training resulted in hypertrophy of the total muscle CSA and fiber areas with no change in estimated fiber number, whereas capillary changes were proportional to muscle fiber growth.
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Fifty college women were randomly assigned to one of three resistance training protocols that employed progressive resistance with high resistance/low repetitions (HRLR), medium resistance/medium repetitions (MRMR), and low resistance/high repetitions (LRHR). The three groups trained on the same resistance exercises for 9 weeks at 3 sets of 6 to 8 RM, 2 sets of 15 to 20 RM, and 1 set of 30 to 40 RM, respectively. Training included free weights and multistation equipment. The 1-RM technique was used for strength testing, and muscular endurance tests consisted of maximum repetitions either at a designated resistance or at a percentage of 1-RM. There were significant pre/post strength increases in both upper and lower body tests, but no significant posttreatment difference in muscular strength among the three protocols. Absolute muscular endurance increased significantly on 4 of 6 pre/post comparisons, while relative endurance increased significantly on only 4 of 12 comparisons. HRLR training yielded greater strength gains. LRHR training generally produced greater muscular endurance gains, and the percentage increase in absolute endurance was approximately twice the increase in strength for all groups. Lower body gains in both strength and endurance were greater than upper body gains.
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An introduction to terms and concepts associated with resistance training is given. Sports associated with this training, such as power lifting and body building, are described. The merits of free weights versus resistance machines are discussed. The article recommends a training program for beginners. (Author/JL)
Article
Fifty college women were randomly assigned to one of three resistance training protocols that employed progressive resistance with high resistance/low repetitions (HRLR), medium resistance/medium repetitions (MRMR), and low resistance/high repetitions (LRHR). The three groups trained on the same resistance exercises for 9 weeks at 3 sets of 6 to 8 RM, 2 sets of 15 to 20 RM, and 1 set of 30 to 40 RM, respectively. Training included free weights and multistation equipment. The 1-RM technique was used for strength testing, and muscular endurance tests consisted of maximum repetitions either at a designated resistance or at a percentage of 1-RM. There were significant pre/post strength increases in both upper and lower body tests, but no significant post-treatment difference in muscular strength among the three protocols. Absolute muscular endurance increased significantly on 4 of 6 pre/post comparisons, while relative endurance increased significantly on only 4 of 12 comparisons. HRLR training yielded greater strength gains. LRHR training generally produced greater muscular endurance gains, and the percentage increase in absolute endurance was approximately twice the increase in strength for all groups. Lower body gains in both strength and endurance were greater than upper body gains. (C) 1994 National Strength and Conditioning Association