Postural Sway Response to Different Forms of Resistance

International Journal of Applied 5ports Sciences
2009, Vol. 21, No. X 64-75.
© Korea Institute of Sport Science
Postural Sway Response to Different Forms of
Resistance Exercise
Bika Zemková
Comenius University Bratislava,
Slovakia
The study prouides an overview of our investigations on tlie ^ct of different
forms of resistance exercise on postural stability. Prior to, during, and after
exeràses the COP velocity zvas registered at 100 Hz by means of posturograpihy
system FiTRO Sway dieck based on dyiiamometric platfiinn. It has beert pund tliat
posttiral siL'ay response to resistance exerdse depends on 1) its intensity (additional
load used), 2) rate of movement, 3) number of repetitions and sets, 4) ¡nusde mass
activated, 5) intensity of proprioceptive stimulation, and 6) type of exeráse.
key ivords Eexercise Intensity, Intensity of Proprioceptive Stimulation, Poshiral
Stability, Rate of Movement, Resistance Exercise, Type of Exercise
Introduction
Currently instability resistance exercises (Zemková, Hamar, 2(X)8) or a combined
agility-balance exercises (Zemková et al., 2(X)9; Zemková, Hamar, 2(X)9) have
became a part of both athletic training and rehabilitation. Underetanding the effect
of different forms of exercise on postural stability may help to design exercise
programs for varioas populatioas including elite athletes, the elderly and those with
coordination problems due to injuty or disease. Though healthy young individuals
are able to maintain balance even after strenuous exercise, for untrained subjects,
the elderly and those with coordination problems even small changes in balance due
to fatigue or hyperventilation induced by exerecise may increase risk of falling and
subsequent injtiry.
There are contraditory results on the effect of resistance exercises on postural
stability. While plantar flexor and dorsiflexor fatigue (Lundin et al., 1993) and
isoldnetic atikle fatigue (Yaggie, McGregor, 2(X)2) adversely affeet balance, fatigued
Received : 15 December 2008, received : 25 February 2009. aeccpled : 12 May 2009
Corresponding author : Erika Zemková (zemková S yahoo.eom)
Pcstural Sway Response to IXfferent Forms of Resistance Exerdse
65
calf-mtascle exercise does not increase postural sway (Adlerton, Moritz, 1996;
Adlerton et al., 2001; Vuillerme et al., 2002). This discrepancy may be due to
different exercise modes used.
However, little is known, for instance, about the role of intensity of
proprioceptive stimulation (e.g., calf rises vs. Jumps) or contraction intensity (e.g.,
explosive vs. slow squats) in post-exercise maintenance of balance. In order to
provide more information on this area of research we compared sway variables after
different forms of resistance exercise.
Methods
A group of PE students volunteered to participate in the smdy (their
characteristics are included in particular studies). Ail of them were informed of the
procedures and on the tnain purpose of the study.
Subjects underwent different forms of exercises (information on particular
protocols can be ftnd in related articles). Prior to and after exercise the COP
velocity was registered at 100 Hz by means of posturography system FiTRO Sway
check based on dynamometric platform (www.fitronic.sk). Subjects were instructed
to minimize postural sway by standing as still as possible. While exercising and
standing on stabilographic platform cardiorespiratory parameters were monitored by
means of breath-by-breath system Spiroergometry CS 200.
Results and discussion
Our experience showed that postural sway respotise to resistance exercises
depends on following factors:
I. Exercise intensity (additional load used)
Parameters of balance were compared (Zemkovä, 2005) after squats performed
with different additional load (% lRM). Results showed (Fig. 1) that COP velocity
was significantly (p < 0.05) higher after squats performed without an additional
66 E
load (AL) as compared to baseline (from 9.1 ± 0.9 mm/s to 12.0 ± 1.4 inm/s).
Slightly higher values were observed after squats performed with AL of 25% lRM
(to 14.5 ± 2.2 mm/s). A significant (p < 0.05) increase was found after squats
performed with AL of 50% IRM (to 20.1 ± 2.6 mm/s). However, there was no
ftirther increase in COP velocity after squats performed with AL of 75% IRM (to
21.4 ± 2.8 mm/s).
These findings indicate that post-exercise (in form of squats) balance impairment
is not linearly related to additional load used.
Figiire 1. Sway vehrity after 10 squats perpnned with different additional load
2. Rate of movetnent
Sway velocity was compared (Zemková, 2005) dtiring barbell squats performed
with different rate of movement. Using FiTRO Dyne Premium (www.fltronic.sk)
a rate of movement was adjusted so that explosive squats were performed with
approximately double the velocity of nonnal squats (184.1 ± 5.0 cm/s and 94.9 ±
2.8 cm/s, respectively) (Fig. 2).
Peak of sway velocity has been found (Fig. 3) to increase by more than double
after barbell squats using explosive cœitractions as compared to normal squats.
There was an increase in COP velocity with each successive repetition tmtil 9. rep
(from 13.6 ± 1.8 mm/s to 23.3 .- 2.5 mm/s and from 32.0 ± 2.9 mm/s to 49.2 ±
3.5 mm/s, respectively) followed by its slight decrease in rep 10. (to 2L1 ± 2.1
tnm/s and to 47.1 ± 3.2 mm/s, respectively).
In summary, sway velocity is more than doubles when performed explosively
over that of tiormal sqtjats with a tendency to increase with subsequent repetitions
up to some point after which a plateau or its sligh decrease tnay be expected.
PiDStural Sway Respraise to Different Forms of Resistarce Exercise
67
250
200
150
100
50
0
Number ot reps
• Nornis< sgauts • Bipkisive squats
Figure 2. Barbell squats performed with different velocity measured by means of FiTRO Di/ne
Premium
^
50
1 40
[ur
r r
[
J
a Normal squaiG D Explosive squats
Figure 3. Siwy velocity during Í0 barbell squats irith an additicnal laui of 50% 1 RM performed
zinth different velocity
3. Number of repetitions and sets
Parametets of balance were compared (Zemková, 2005) after a different number
of repetítiotis and sets of squats. Other factors (e.i., kilogratns lifted, acceleratioti
rate with which loads were raised, rest intervals, etc.) that could confound the
overall workout inteasity were statidardized.
Results showed that sway velocity significantly (p < 0.05) increased with
increasing number of repetitions (from 5 to 20 reps) (Fig. 4).
Similarly, as the nutnber of sets increased also sway velocity significatitly (p <
0.05) increased (from 2 to 4) followed by its slight rise toward set 5 (Fig. 5),
Taken together, sway velocity increases rather proponionally to the tiumber of
reps and sets. However, there is no further rise in its values when a certain point
is reached (e.g., after 4 sets of 15 reps with AL of 50% IRM).
68 E Zemková
35
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20
Nuni>ef of raps
4. Sîvay velodty after different number of reps of barbell squats with an additional load of
50% IRM
5. Szvay velodty afier 5 sets of 15 barbell squats with an additional load of 50% IRM
4. Muscle mass activated
Parameters of balance were eonipared (Zemková et al., 2(X)6) after different
forms of resistance exercise and after voluntary hyperventilation. A group of PE
snidents performed 20 squats, calf rises, biceps curls, and presses behind the neck
with an additional load of 50% IRM. In addition to this, they hyperventilated for a
corresponding time to the duration of the exercises. Tldrty secotids priOT to and two
minutes after exercises the COP velocity was registered at 100 Hz by means of a
posturography system FiTRO Sway Check based on dynamometric platform. While
exercising and standing on the platform, parameters of ventilation and heart rate
were continuously tiïonitored using breath-by-breath system MMC Horizon
Sensormedics.
Results showed (Fig. 6) the highest increase in COP velocity after squats (16.4 ±
BDBtural
Response to Different Rirtns of Resistance Exerdse
69
1.4 mm/s), following ealf rises (15.2 ± 1.3 mm/s), voluntary hyperventilation (14.8 ±
1.2 mm/s), biceps curls (14.0 ± 1.1 mm/s), and presses behind neck (13.6 ± 0.8
mm/s). In all cases a predotiiinant shift in medio-lateral (10.1 mtn/s, 9.3 mm/s, 8.5
mm/s, 8.2 mm/s) than antero-posterior direction (6.3 mm/s, 5.9 mm/s, 5.5 mm/s, 5.4
was found.
BICEPS CURLS
PRESSES BEHIND NEC«
HYPERVENTILATION
Figure 6. COP velocity prior to and after resistance exerdses and voluntary hyperventilation
Likewise, the highest ventilation (Fig. 7) was found after squats (59.1 ± 6.6
1/min), then after calf rises (48.2 ± 5.8 I/min), voluntary hyperventilation (44.1 ± 5.2
1/min), biceps eurls (40.0 ± 4.6 I/min), and presses behind neck (38.9 ± 3.8 1/niin).
Also heart rate (Fig. 8) was the highest after squats (165.0 ± 7.2 beats/min),
following by calf rises (135.0 ± 6.8 beats/min), biceps curls (129.2 ± 5.8 beats/min),
presses behind neck (125.1 ± 4.6 beats/min), and voluntary hyperventilation (117.2 ±
4.8 beats/min). In all parameters a significant (p < 0.01) increase when compared to
pre-exercise level has been found (8.6 ± 0.2 tntn/s, 12.3 ± 0.1 1/min, and 76.5 ± 1.8
beats/tnin, respectively).
There was also a close correlation between sway velocity and ventilation in an
intitial phase of recovery after squats (r = 0.939), calf rises (r = 0.919), biceps curls
(r = 0.896), and behind the neck presses (r = 0.889). This indicates that impairment
of postural stability in an early phase of recovery after resistance exercises is very
probably due to more pronounced ventilation.
In addition, sway velocity after voluntary hyperventilation reached a maximum
at the etid of exercise and started to deeline immediately in the recovery phase. In
contrast, its values after resistance exercises, particularly after those performed with
lower extretnities, remained temporarily elevated and only after about 25 and 10
70 E
seconds a gradttal decrease back to the resting level set in. Though this effect may
be tnainly a cotisequence of delayed activation of ventilaticm in an early phase of
recovery after such exercises, some contribution of fatigue cannot be excluded.
However, our finding showed that impairment of
recovery after resistance exercises is a consequence
rather than fatigue. This effect is tnore evident after
lower (squats and calf rises) rather than the upper
presses behind neck).
balance in an early phase of
of more tnarked ventilation
exercises performed with the
extremities (biceps ctirls and
B1CE9S CURLS
POUSSES SEHIND NECK
Figure 7. Ventilation before, during and afler resistance exerdses and voluntary hyperventilation
e l f RISES
BICEPS CUFtLS
PRESSES BEHirJD N B
HYPERVENTILSTION
Figure 8. Heart rate before, during and after resistance exerdses and voluntary hyperventilation
5. Intensity of proprioceptive stimulation
Parameter of balance were compared (Zemková et al., 2005) after two forms of
Fbstural Sway Respcnse to Different Forms trf ResLstaire B^nse
71
resistance exercise leading to the same vetitilation, however with different intensity
of proprioceptive stimulation. A group of PE students underwent on different days
two lower limbs resistance exercises in the form of calf rises and vertical rebound
jumps. Med-onome was employed to guide the frequency of repetitions at the rate of
1 Hz. Calf rises were performed for 60 seconds. Jumps were finished as soon as
ventilation reached the level achieved during previously performed calf rises (on
average after 50 seconds). Ventilation was monitored by tneans of breath-by-breath
system MMC Horizon. A level of exertion was estitnated at the end of exercises
using Borg's 6 to 20 Rating of Perceived Exertion Scale (1970). One minute prior
to and two minutes after exercises the velocity of the centre of pressure (mean and
in antero-posterior and medio-lateral directions) was registered at 100 Hz by means
of the posturography system FiTRO Sway Check based on dynamometric platform.
Average values of 5-second intervals were used for the evaluatioa
As intended, in an initial 5-seconds phase of recovery there were no significant
differences in ventilation after jumps and calf rises (26.4 and 26.5 1/min,
respectively) (Fig. 9). However, in the same period significantly (p < 0.01) higher
increase in COP velocity after jumps (ftxtm 8.9 to 24.1 mm/s) as compared to calf
rises (from 9.1 to 18.8 mm/s) has been registered (Fig. 10). In addition, its values
after jumping retnained temporarily elevated with a slight tendency to increase and
only after about 25 seconds a gradual decrease back to the resting level set in. On
the other hand, COP velocity after calf rises started to decrease within 5 seconds of
recovery. In addition, a higher increase in medio-Iateral (8.4 and 5.8 mm/s,
respectively) than in antero-posterior direction (5.0 and 3.9 mm/s, respectively) has
been found. All subjects perceived both exercises as veiy hard, corresponding to a
rate of 18 on the Borg's RPE scale.
As is known from biomechanical analyses, substantially higher vertical ground
forces are produced during jumps as compared to calf rises. It may be assumed that
more profotind stimulation of muscle spindles, tendon organs, joint receptors and
cutaneous mechanoreceptois on the sole during jtimps has been provided leading to
the impairment of their sensitivity. Resulting in partial reduction of afferent impulses
leading to deterioration in proprioceptive feedback control of balance after jumping
very probably contributed to some 60% to the approximately double increase in sway
velocity relative to pre-exercise values already registered after calf rises.
In other words, intensity of proprioceptive stimulation during resistance exercise
has an important influence on feedback mechanisms involved in control of balance.
72 E Zanková
30
25
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9. VcnÜlation prwr to, during, and after calf rises, and jumps
RECOVB« FHftSE
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CALF RSES
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10. Sway velocity before and after calf rises and jumps
6. Type of exercise
Previous investigatiotis showed (Zemková et al, 2006) greater postural sway
after exercises perfonned with the lower (squats and calf rises) rather than the upper
extremities (biceps curls and prases behitid neck) due to more tnarked ventilatioti.
Further, intetisity of proprioceptive stimulation was found (Zemková et al., 2005) to
be respoasible for more profound balance impairment after jumps than after calf
rises.
In this study (Zemková, 2005), parameters of balance were compared after
different types of resistance exercises (calf rises and sustained stance on tiptoes)
matched the same work fe.i,, load x reps).
Postural Sway Respaise to Different FCTTTTB of Resistance Exercise
73
There was no difference in sway velocity after 60 calf rises performed with AL
of 50% IRM and 40 calf rises performed with AL of 75% IRM (22.5 ± 4.2 mm/s
and 21.1 ± 5.8 mm/s, respectively) (Fig. II).
Similarly, no difference was found between trials after maintaining a tiptoe stance,
however, sway velocity was slightly greater as the barbell weight increased and the
time of exercise was shorter (12.9 ± 2.1 mm/s, 16.3 ± 2.4 mm/s, and 17.9 ± 2.8
mtn/s, respectively) (Fig. 12). It means that postural sway response to isometric
exercise in the form of a sustained tiptoe stand depends cm its duration (t) and an
additional load used (F).
20
50
75
Adc]llkinalk]ad(%iRM)
Figure 11. VSway velodty after different number of calf rises performing with an additional load
of 50% and 75% ÎRM. respectively
25
-
-
25
50
75
Additional load (% 1F%I)
Figure 12. Sway velodty after a sustained tiptoe stance of different duration perpnning with an
additional load of 25%, 50%, and 75% IRM respectively
74 E Zemková
Conclusion
Postural sway response to resistance exereise depends on I) its intensity
(additional load used), 2) rate of movement, 3) number of repetitions and sets, 4)
muscle mass activated, 5) intensity of proprioceptive stimulation, and 6) type of
exercise. More specifically:
1) Post-exercise (in the form of squats) postural sway is noi linearly related to
additional load used (e.g., its values only slightly rise after squats performed with
AL of 50% lRM);
2) Sway velocity is more than double when performed with explosive rather than
normal squats with a tendency to increase with subseqtient repetitions up to some
point after which a plateau or slight decrease may be observed (e.g., after 9 reps);
3) Sway velocity increases rather proportionally to the number of reps and sets.
However, there is no further rise its values when a certain point is reached (e.g.,
after 4 sets of 15 reps with AL of 50% lRM);
4) Impairment of balance in an early phase of recovery after resistance exercises
is a consequence of more tnarked ventilation rather than of fatigue. This effeet is
more evident after exercises perfonned with the lower (squats and calf rises) ratter
than the upper extremities (biceps curls and presses behind neck);
5) Intetisity of propioceptive stimulation during resistance exercise has an
important influence on feedback mechanisms involved in control of balance (e.g.,
there is a higher COP velocity after jumps than after calf rises);
6) There is no difference in COP velocity after calf rises performed with higher
additional load (AL) in fewer reps and those with lower AL in more reps. A slight
increase after a sustained tiptoe stand with a higher AL for a shorter time rahther
than after those with a lower AL for a longer time ttiay be observed. This indicates
that postural sway response to sueh an isometrie exercise depends on duration (t)
and additional load used (F).
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