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Utility of the Powerball in the invigoration of the musculature of the forearm.

Authors:
  • Institute Kaplan

Abstract and Figures

In order to ascertain the utility of a 250 Hz NSD Powerball gyroscope in increasing the maximum grip force and muscular endurance of the forearm, ten adults without pathology in their upper limbs exercised one forearm with the device during a period of one month. We evaluated grip strength and forearm muscle endurance with a Jamar dynamometer both at the end of the month as well as after a resting period of one month. There was a tendency (not statistically significant p = 0.054), for the volunteers to increase their maximum grip strength. There was also highly significant increase in muscle endurance (p = 0.00001), a gain that remained slightly unchanged after the rest. Because the gyroscope generates random multidirectional forces to the forearm, the reactive muscle contraction is likely to stimulate more efficient neuromuscular contro of the wrist, a conclusion which our work appears to validate. The use of Powerball in forearm proprioception deficient patients is, therefore, justified.
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Hand Surgery, Vol. 13, No. 2 (2008) 79–83
© World Scientific Publishing Company
UTILITY OF THE POWERBALL®IN THE INVIGORATION OF THE
MUSCULATURE OF THE FOREARM
Sebastián Axel Balan and Marc Garcia-Elias
Institut Kaplan,Barcelona,Spain
Received 22 August 2008; Accepted 10 October 2008
ABSTRACT
In order to ascertain the utility of a 250 Hz NSD Powerball®gyroscope in increasing the maximum grip force and muscular
endurance of the forearm, ten adults without pathology in their upper limbs exercised one forearm with the device during a period
of one month. We evaluated grip strength and forearm muscle endurance with a Jamar dynamometer both at the end of the month
as well as after a resting period of one month. There was a tendency (not statistically significant p =0.054), for the volunteers to
increase their maximum grip strength. There was also highly significant increase in muscle endurance (p =0.00001), a gain that
remained slightly unchanged after the rest. Because the gyroscope generates random multidirectional forces to the forearm, the
reactive muscle contraction is likely to stimulate more efficient neuromuscular control of the wrist, a conclusion which our work
appears to validate. The use of Powerball®in forearm proprioception deficient patients is, therefore, justified.
Keywords: Gyroscope; Grip Force; Endurance; Proprioception.
INTRODUCTION
In most sports, as rehabilitation of different pathologies of the
upper limb, there is a need for incrementing force of the mus-
culature of the forearm. Several devices with fixed weights have
been created for different muscular groups to work with: cuff
links and bars, bands of tension, jetty pincers. Not long ago,
an apparatus appeared in the market, developed to carry out
exercises of muscular build-up of the upper extremity, based
on the principles of gyroscope.1,2 It is a hollow sphere that
contains in the interior a rotor of 200 grammes of weight with
an eccentric mass located two centimetres away from its axis.
This internal cylinder rotates around an axis which is perpen-
dicular to the main axis. The internal rotor moves not so much
as a result of its fixed weight (single weight 280 grammes)
but by the generated centrifugal force. When the internal rotor
Correspondence to: Dr. Marc Garcia-Elias, Institut Kaplan, Passeig de la Bonanova, 9, 2nd floor, 2nd door - 08022, Barcelona, Spain. Tel: (+34) 93-417-8484,
Fax: (+34) 93-211-0402, E-mail: garciaelias@institut-Kaplan.com
There is no interest in commercialization with the product (250 Hz NSD Powerball®) by the authors and no financial association.
is accelerated, generates a torsion force that causes a turn in
the perpendicular plane, and because the eccentric disposition
of its mass, a rotational force to the rotor is generated up to
10,000 revolutions per minute. The gyroscope accelerates by
means of movements of wrist rotation. As the speed of the rotor
of the gyroscope increases, the centrifugal force increases and,
therefore, the necessity of muscular control becomes increas-
ingly bigger. This work was designed in order to ascertain if
this device induces significant changes in both the maximal grip
strength and muscular endurance, understanding this last factor
is the most important parameter in most activities.
MATERIAL AND METHODS
Ten adults, five men and five women, participated in this study.
None had antecedents of traumatic lesion or pathology in both
79
80 S. A. Balan & M. Garcia-Elias
Fig. 1 250 Hz NSD Powerball®.
Fig. 2 Another view of the 250 Hz NSD Powerball®.
upper limbs and were not carrying out any other build-up plan
during this project. Each volunteer was given a 250 Hz gyroscope
(NSD Powerball®). The study was divided into two periods of
four weeks each. The volunteers exercised the dominant upper
extremity in two daily series of three minutes in the first two
weeks and two daily series of five minutes in the last two weeks.
In the second period they did not carry out any muscular invig-
oration. The exercise was performed while seated, with the
elbow flexed at 90, and leaning on a firm surface. Rotation of
the gyroscope was driven with wrist turning clockwise in case
of the right arm dominant volunteers and counter-clockwise in
case of left-handed volunteers. In all cases, the overall wrist
envelope of rotation was set around a slightly extended-ulnar
deviated position, and always trying to develop the maximum
possible speed that could be maintained and controlled com-
fortably during the whole exercise. The contralateral upper limb
did not carry out any build-up work and it was used as the con-
trol. Each person was given a chart to document the exact timing
and incidences of all their exercises.
Evaluation of Force
Both upper limbs were assessed before and after the first period
of exercises, and again after a month of rest. The grip strength
Powerball®Utility in Invigoration of Forearm Musculature 81
Fig. 3 Powerball ready to work.
Table 1 Maximal Grip Force and Endurance Index Results.
Volunteer MaxGF (Initial) kg. MaxGF (1st Mth.) kg. MaxGF (2nd Mth.) kg. Ei (Initial) Ei (1st Mth.) Ei (2nd Mth.)
(A) 29 44 40 16 24 31
(B) 28 35 37 15 39 20
(C) 51 63 53 18 36 31
(D) 41 52 55 24 41 48
(E) 56 54 57 18 29 37
(F) 35 36 30 15 29 32
(G) 26 24 19 10 33 24
(H) 37 31 33 13 39 26
(I) 21 30 30 11 16 11
(J) 56 60 52 17 30 28
Average 38 42.9 40.6 15.7 31.6 28.8
Median 36 40 38.5 15.5 31.5 29.5
SD 12.7 13.6 13 4 7.7 9.9
MaxGF: Maximal grip force, Ei: endurance index, SD: standard deviation.
was measured with a Jamar®dynamometer3in the position two
or three depending upon the patient’s comfort. With the shoul-
der relaxed, the elbow flexed at 90, the forearm leaning on
the examination table in neutral forearm rotation and the wrist
extended at 25.4To obtain maximum grip force the volunteers
were requested to compress the two bars of the dynamometer
as hard as possible, alternating both hands. The highest reading
from three attempts was used in this study.
82 S. A. Balan & M. Garcia-Elias
To evaluate muscular endurance,5,6 we established the follow-
ing assessment method. The volunteers were asked to alternate
periods of three seconds of maximal contraction with three
seconds of relaxation until the digital reading was equivalent to
40% of the maximum grip force determined earlier. The num-
ber of contractions above that level was used as an expression
of muscular endurance of each individual.
The participant volunteers were not informed of their results
until all assessments were finished. All tests were monitored by
the same investigator.
The Student’s t-test for matched samples was used to settle
down differences in the studied parameters between the two
arms, and a p-value of <0.05 was utilised as the threshold of
significance.
RESULTS
The average maximum grip force (MaxGF) of the dominant hand
prior to the exercise period was 38 kg [range 21–56; standard
deviation (SD): 12.7], and the average muscular Endurance
Index (EI) was 15.7 contractions (range 10–24; SD: 4).
After the first period of one month exercising regularly with
the gyroscope, the average MaxGF was of 42.9 kg (range 30–
63; SD: 13.6). This corresponds to an increase of 15% as
compared to the initial determination, and although the gain was
not significant, the tendency for an increase in this parameter
was clear (p =0.054). The average EI was 31.6 contractions
(range 16–41; SD: 7.7) representing an increase of 109%,
which is highly significant (p =0.00001). After the same
period the non-dominant arm did not increase either in MaxGF
(p =0, 45) or in EI (p =0, 065).
After the second period of one month where no exercises
were carried out, the average MaxGF diminished slightly down
to 40.6 kg (range 19–57; SD: 13), although that decrease of
5.3% was not statistically significant with regards to what was
achieved at the end of the first period (p =0.17). Similarly, the
average EI decreased down to 28.8 contractions (range 11–48;
SD: 9.9), but that 7.7% reduction was not statistically significant
(p =0.36). Not surprisingly, the differences between the initial
and final recordings of both MaxGF and EI remained highly
significant (p =0.00001).
DISCUSSION
The results of this study appear to prove the hypothesis that
regular use of a gyroscope for one month does not develop
the capacity of maximum contraction of the musculature of the
forearm but increases its endurance substantially. Indeed, the
increment of the number of contractions beyond a certain level
after a month of exercises was remarkably high. Furthermore,
it appears to remain high for an extended period of at least one
more month of not using the apparatus. As this last parameter is
one of the most trustworthy ones for the evaluation of muscular
invigoration, it is apparent that gyroscopes may have a role in our
future treatment armamentarium. Contrary to other more static
devices, the gyroscope generates forces in different directions,
in a quite random way, forcing the musculature of the forearm
to react in an unpredictable way, thus stimulating propriocep-
tion. In these regards, this device may be found particularly
useful in patients with congenital or acquired hyperlaxity having
developed wrist dysfunction secondary to poor proprioceptive
neuromuscular control.
Although debatable, we believe that the muscular control that
is required to counteract the centrifugal forces generated by this
sort of apparatus is in fact an eccentric exercise, inducing active
fibre elongations.79In other words, this sort of exercise does
not imply a reduction of the muscular fibre length as when the
extrinsic activity of the muscle is propitiated.9
Needless to say, although this device may be useful for reha-
bilitation of different pathological conditions, it should be used
carefully. Although none of the volunteers experienced signifi-
cant pain nor discomfort with its use, the generated force may
become quite important and, as shown in different studies,
eccentric exercises in weak or improperly trained muscula-
tures have potential for a higher pain index and damage of the
muscular ultrastructure.10,11
References
1. Deimel R, Mechanics of the Gyroscope: The Dynamics of Rotation,
Dover Publications, 1950.
2. Scarborough JB, The Gyroscope, Theory and Applications, Interscience,
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3. Mathiowetz V et al., Reliability and validity of grip and pinch strength
evaluations, J Hand Surg [Am] 9(2):222–226, 1984.
4. Mathiowetz V et al., Grip and pinch strength: normative data for adults,
Arch Phys Med Rehabil 66(2):69–74, 1985.
5. Yamaji S et al., The influence of different target values and measurement
times on the decreasing force curve during sustained static gripping work,
J Physiol Anthropol 25(1):23–28, 2006.
6. Watts P, Newbury V, Sulentic J, Acute changes in handgrip strength,
endurance, and blood lactate with sustained sport rock climbing,
J Sports Med Phys Fitness 36(4):255–260, 1996.
Powerball®Utility in Invigoration of Forearm Musculature 83
7. Goslow G Jr, Reinking R, Stuart D, The cat step cycle: hind limb joint
angles and muscle lengths during unrestrained locomotion, J Morphol
141:1–42, 1973.
8. Hoffer JA et al., Roles of muscle activity and load on the relationship
between muscle spindle length and whole muscle length in the freely
walking cat, Progr Brain Res 80:75–85, 1989.
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injury, prevention, rehabilitation and sport, J Orthop Sports Phys Ther
33(10):557–571, 2003.
10. Evans WJ et al., Metabolic changes following eccentric exercise in trained
and untrained men, J Appl Physiol 61:1864–1868, 1985.
11. Fridén J, Lieber RL, The structural and mechanical basis of exercise-
induced muscle injury, Med Sci Sport Exerc 24:521–530, 1992.
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Twenty-seven college women participated in a study to evaluate the reliability and validity of four tests of hand strength: grip, palmar pinch, key pinch, and tip pinch. Standardized positioning and instructions were followed. The results showed very high inter-rater reliability. Test-retest reliability was highest in all tests when the mean of three trials was used. Lower correlations were shown when one trial or the highest score of three trials were utilized. The Jamar dynamometer by Asimow Engineering and the pinch gauge by B&L Engineering demonstrated the highest accuracy of the instruments tested.
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Modern rock climbers stress the importance of hand-to-rock contact strength as a factor for success in competitive sport climbing events, however, the degree of handgrip fatigue that occurs during difficult climbing and the time course of recovery from fatigue have not been previously described. The purpose of this study was to characterize the nature of handgrip fatigue that results from difficult continuous climbing until a fall occurs. Eleven expert-level rock climbers (age = 28.7 +/- 4.5 years) volunteered to climb continuous laps over a pre-set competition-type route on an indoor modular climbing wall until a fall occurred. The route difficulty (YDS rating of 5.12 a) was near the limit of each subject's "on-sight" lead climbing ability and placed an emphasis on physically difficult movements. "On-sight" refers to a climbing style where the climber ascends the route on the first try without falls and without prior viewing or information about the route. Practice was allowed to enable each subject to master the individual technical movements of the route. Fingertip blood samples were obtained 10 min pre-climb, at post-climb, and at 5-, 10-, and 20-min recovery and analyzed for lactate. Maximum handgrip force in Newtons was determined via dynamometry for each hand and averaged for pre-climb, post-climb, and 5-, 10-, and 20-min recovery periods. Right handgrip endurance, defined as the time that the dominant hand handgrip force could be sustained above 70 percent of handgrip strength, was determined pre-climb, post-climb, and at 20-min recovery. Mean climbing time during testing was 12.9 +/- 8.5 min for 2.8 +/- 2.2 laps over the route. Data among measurement times were analyzed using a repeated measures ANOVA with Newman-Keuls post hoc tests. Handgrip strength decreased by 22 percent and handgrip endurance decreased by 57 percent from pre-climb to post-climb and both remained depressed after 20 minutes of resting recovery. The pre-climb blood lactate of 1.4 +/- 0.8 mmol.l-1 significantly increased to 6.1 +/- 1.4 mmol.l-1 at post-climb and remained elevated (2.3 +/- 0.8 mmol.l-1) at 20-min recovery. Percent decreases in handgrip strength were significantly correlated with climbing time (R = 0.70), number of laps completed (R = 0.70), and blood lactate (R = 0.76). Percent decreases in handgrip endurance were significantly correlated with climbing time (R = 0.70) and number of laps completed (R = 0.80), but not with blood lactate (R = 0.56). It was concluded that handgrip strength and handgrip endurance decrease with continuous difficult rock climbing and remain depressed after 20 minutes of resting recovery. It also appears that handgrip strength recovers at a faster rate than handgrip endurance.