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

  • 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
Sebastián Axel Balan and Marc Garcia-Elias
Institut Kaplan,Barcelona,Spain
Received 22 August 2008; Accepted 10 October 2008
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.
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:
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.
Ten adults, five men and five women, participated in this study.
None had antecedents of traumatic lesion or pathology in both
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
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).
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
1. Deimel R, Mechanics of the Gyroscope: The Dynamics of Rotation,
Dover Publications, 1950.
2. Scarborough JB, The Gyroscope, Theory and Applications, Interscience,
New York, 1958.
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.
9. La Stayo P et al., Eccentric muscle contraction: their contribution to
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.
... The NSD PowerBall® system [19,20], based on the principle of a gyroscope, was developed for upper limb strengthening and has shown positive results in results in increasing grip strength and reducing non-speci c elbow pain. The device consists of a sphere containing a 200-gram rotor with an eccentric mass located 2 cm from its axis. ...
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Introduction Clinical impairment of the upper limbs (UL) in patients with multiple sclerosis (MS) is very common. Muscle strength and hand dexterity are critical factors in maintaining functional activities that are the basis for independence and quality of life. Objective Investigate the effects of a training protocol using the NDS-Powerball® system in combination with conventional physiotherapy on muscle strength, coordination, fatigue, functionality, and quality of life in persons with MS over an 8-week period. Materials and Methods A double-blind randomized controlled trial with two intervention groups was conducted. The control group received conventional treatment, while the experimental group received additional UL training using the NDS-Powerball® system. Both groups received the same number of sessions and weeks of intervention. The following outcome measures were used: isometric grip and pinch strength, Box and Block Test (BBT), Nine Hole Peg Test (NHPT), Abilhand scale, Fatigue Severity Scale (FSS), Multiple Sclerosis Impact Scale (MSIS-29), and Likert satisfaction questionnaire for the experimental group. All measures were administered at baseline, after the treatment, and during a 3-week follow-up period. Results 25 patients completed the study (12 persons with MS and 13 healthy control subjects). The experimental group showed significant improvements in coordination and manual dexterity of the more affected UL as measured by the BBT comparing pre- to post-treatment (p = 0.048) and pre-treatment to follow-up (p = 0.001), and on the less affected UP comparing pre-treatment to follow-up (p < 0.001) and post-treatment to follow-up (p = 0.034). The Likert-type satisfaction questionnaire obtained a mean score of 89.10 (± 8.54) out of 100 points. Conclusions An UL treatment protocol using the NDS-Powerball® system, in combination with conventional physiotherapy for 8 weeks resulted in significant improvements in the intra-group analysis for UL coordination and manual dexterity in favor of the experimental group. The experimental group showed excellent satisfaction to the treatment.
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Background: Lateral epicondylitis (LE), most commonly referred to as Lateral Elbow Tendinopathy (LET) or Tennis Elbow is one of the commonest repetitive stress syndromes seen in elbow joint. Tendinopathy, an injury to forearm extensor muscles. These muscles arise from the distal end of humerus from lateral epicondylar region. In many cases, involvement of extensor carpi radialis brevis muscle’s insertion is seen. This study focuses on the treatment of a person with LE which occurs in repeated upper extremity movements. There is no such research relevant to PowerBall device exercises on Lateral epicondylitis patients' pain and function. “PowerBall device” exercise is considered to be an effective resistance training, putting extrinsic and intrinsic pressure on wrist, elbow and shoulder muscles and has been shown to improve strength, function, ROM, tennis elbow pain and quality of life. Whereas MMWM has been proven to reduce the pain in patients with LE. Methods/Design: The participants (n=50) with lateral epicondylitis will be included in a single-blinded, randomised control trial. Participants will be categorised into either a control group or an intervention group after performing baseline assessments and randomization. The participants in the control group will be given Mulligan Mobilisation with Movement, and those in the intervention group will be given “PowerBall device” exercise and conventional physiotherapy. Basic exercises and ultrasound will be given to both groups with the given protocol. We will evaluate pain, function, grip strength and Range of motion, pre and post intervention period. Discussion: Efficacy of the intervention is evaluated by analysing the pain and function in patients with lateral epicondylitis using PRTEE scale, and grip strength using Hand-held Dynamometer. The results from the study will significantly provide affirmation on the application of “PowerBall device” exercise and Mulligan Mobilisation with Movement on the patients with lateral epicondylitis.The clinical trial registry-India(CTRI) registration number for this trial is CTRI/2021/05/033363.
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Background and Aims: Muscles around the shoulder are important for its dynamic stability. Strengthening them is a necessity of muscle rehabilitation. This study attempted to investigate the effect of Powerball (as a relatively new method) on shoulder muscles strengthening exercises. Materials and Methods: Seventy-five healthy subjects were randomly divided into experimental (n =50) and controls (n=25) groups. Evaluation of shoulder muscles activity was conducted using electromyography of middle deltoid, upper Trapezius, Latissimus dorsi and Infraspinatus muscles in 90 degree arm abduction with an active powerball (experimental group) and an inactive powerball (control group) immediately and again after 12 days of training.
Objective The aim of this study was to determine the effect of using the Powerball gyroscope as a treatment device on pain and change in endurance in nonspecific wrist pain. Methods This study was a within-participants pre- and postintervention study consisting of 40 participants between ages 18 and 35 with an equal male-to-female ratio. The participants used the Powerball gyroscope for 5 minutes per treatment session. Treatment comprised 12 sessions carried out 3 × per week over a 4-week period. Participants completed objective and subjective data before the first, seventh, and 12th sessions. Objective data were recorded using the Jamar dynamometer to measure grip strength. Subjective data were gathered using the Patient-Rated Wrist Evaluation Questionnaire. Participants then used the Powerball gyroscope in the hand with the affected wrist. The Wilcoxon signed rank test and 1-way repeated-measures analysis of variance were used to analyze the changes. Results A significant decrease in pain was noted throughout the study, but the most significant changes occurred between the seventh and 12th treatment sessions (P < .01). A significant increase in grip strength was also noted throughout the study, with the greater increase in grip strength occurring during the first 7 treatments (P < .02). Conclusion The Powerball gyroscope showed a change in outcome regarding nonspecific wrist pain and grip strength.
This chapter will focus on fundamental elements of hand rehabilitation including the need for proprioception training and orthotic use. In the context of minimally invasive hand surgery, innovative contemporary hand rehabilitation strategies are needed.
Sporting rehabilitation depends essentially on anatomical and biomechanical knowledge, lesion mechanisms, and the trauma or overuse pathology of the sport in question. This chapter concerns the early care of injured athletes, specific rehabilitation protocols, and finally the return to competitive activity, considering the whole psychological and social sphere linking athletes to their injury. We consider the main lesions of the hand and wrist as fractures, avulsion, dislocations, impingement, and tendinitis affecting athletes practicing combat sports. We investigate how conservative and postsurgical rehabilitation, with essential support from splints and edema reduction by taping techniques, can restore the athlete to competitive sporting activity as soon as possible, without violating the healing times of different tissues. The timing of rehabilitation is that of specific protocols found in the literature for the finger, metacarpal, and wrist trauma, likewise for immobilization, edema reduction, and pain treatment. Athletes are allowed to resume early sporting activity, thanks also to protective splints, paying special attention to movements and psychological effects of the injury. Treating anatomical areas with a high prevalence of tendon, ligament, and joint capsule receptors, proprioceptive recovery is necessary in order to obtain an optimum stability and orientation of hand and wrist.
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The purposes of this study were to clarify the decreasing properties of, and to examine useful measurement times for evaluating muscle endurance in a comparison among various parameters using measurement times of 1, 3 and 6 mins and target values of 50, 75 and 100% MVC. Fifteen males and 15 females participated in this study. All subjects carried out sustained isometric gripping under nine conditions of measurement times and target forces, (1, 3 and 6 mins vs. 50, 75 and 100% MVC) with an interval of one or two days. The property of decreasing force in the initial phase (marked decreasing phase) differed among the target values, and the decreasing speed of the gripping force was highest for 100% MVC. However, the decreasing property after about 60 sec, in which the force decreased to about 30% MVC from the onset of grip, was similar among all target values, and then the gripping force reached an almost steady state phase at about 150-180 sec. In other words, the difference of the decreasing property during the initial phase with different target values was considered not to influence the property in the later phase, in which the force decreases to about 30% MVC. When muscle endurance is evaluated from the phase until reaching the steady state, it may be possible to evaluate the same property of the decreasing phase at 6 min as the measurement at 3 min. The measurement for 1 min at 50% MVC was not valid as an evaluation time because the grip force did not decrease enough. The integrated area in the initial phase was considered to depend on the magnitude of the target value, and the integrated area for 30 sec or 60 sec at 75% MVC was larger than that at 100% MVC. It was inferred that higher pain at 100% MVC resulted in a greater decrease in the speed of the force.
The objective of this research was to compare the length of muscle spindles to the length of the whole muscle, during normal movements. Pairs of piezoelectric crystals were implanted near the origin and insertion of muscle fibres in the medial gastrocnemius (MG) muscle of cats. The distance between crystals was measured with pulsed ultrasound, the origin-to-insertion length of the MG muscle was measured with a transducer made of saline-filled silicone tubing, MG force was measured with a tendon force transducer and EMG activity was selectively recorded in the vicinity of implanted crystals. These signals were simultaneously recorded during posture or locomotion on a motorized treadmill. Three periods were identified in the step cycle, during which the relation between muscle length and spindle length changed dramatically. In period I (roughly corresponding to the late F and E1 phases of swing), the MG muscle and spindles followed similar length changes: both were stretched and then shortened by about 6 mm. In period II (corresponding to the stance phase, E2-E3) the MG muscle yielded under the weight of the body and was stretched by 1-3 mm, whereas the MG spindles typically continued shortening. In period III, the MG muscle shortened rapidly by 6-8 mm after the foot left the ground and then stretched again by about the same amount, whereas the spindles could remain nearly isometric. We attribute these large discrepancies in muscle and spindle length to the architecture of the MG muscle and the compliance of long tendinous elements in series with the spindles. We conclude that the length changes imposed on muscle spindles during voluntary movements are not simply related to the parent muscle length changes and cannot be estimated without taking into account the muscle architecture, the location of the spindle within the muscle, the level of muscle activation and the external load.
A cinematographic analysis of the unrestrained walking, trotting, galloping, jumping and landing movements of 11 adult cats was undertaken to provide previously unavailable information concerning the demands imposed on the nervous system for the control of low and high speed movements and the demands imposed by such natural movements on muscle performance and proprioceptive response. With due regard for the swing (F and E ¹ ) and stance (E ² and E ³ ) phases of the step cycle of an individual limb, single frame analysis of the film permitted measurement of instantaneous angles of the lower spine, hip, knee, ankle and metatarsophalangeal joints. Appropriate lever arm measurements were also made on 50 freshly dispatched cats and 25 cadavers such that the Law of Cosines could be used to calculate instantaneous lengths of select hind limb muscles that would apply to the natural movements of adult cats of small (1.5–2.5 Kg), intermediate (2.6–3.5 Kg) and large (3.6–4.5 Kg) size. Muscle displacements were analyzed relative to maximum and minimus in situ lengths and the lengths associated with quiet standing. Use was also made of a previous electromyographic analysis of hind limb muscles during unrestrained locomotion (Engberg and Lundberg, '69). The sequential relations between the four phases of the step cycle are maintained as forward speed increases from walking ( < 2 mph) to high speed galloping ( > 16 mph). There are significant differences in the time consumed by each phase, however, with a greater reduction in the E ³ phase, little reduction in the E ² and E ¹ phases and virtually no reduction in the F phase. When each phase is expressed as a relative percentage of the duration of the total step cycle, the greatest reduction is again in E ³ with little change in the E ² phase. In contrast F and E ¹ phases increase in the percent of time they occur in each cycle, with the greatest increase in the F phase. For all speeds, analysis of the phase relations between movements of various sections of the hind limb revealed a remarkable unity of knee and ankle joint movement. The hip joint is largely out of phase with the knee and ankle during E ¹ and E ² , all three joints being in phase in F and E ³ . The digits are essentially out of phase with the other joints except in the stance phase of the gallop. Rates and extents of muscle displacement during natural movements are greater than might be anticipated when expressed in absolute mm's and mm/sec but not when considered in relation to maximum and minimum in situ length and the length associated with quiet standing (Ls). During stepping a progressive increase in forward speed results in: (a) a greater usage of muscles at lengths between Ls and maximum in situ length; (b) for knee and ankle extensors, pronounced increase in the lengthening contraction associated with the E ² (yield) phase of step; and, (c) for both flexor and extensor muscles, an increased active phase of lengthening or near isometric contraction immediately prior to periods of active shortening. In contrast to these changes in active muscle status, the change from walking to galloping has little effect on the extent and rate of passive muscle displacements, particularly the F phase stretch of extensors. For the soleus muscle, calculations were made of the relation between changes in overall muscle length during natural movements and the length of the average muscle fiber and the tendon of insertion. These measurements revealed that the increases in fiber length when passive and decreases in length during active shortening are less than would be anticipated from the extensive liteature on extirpated fibers. In contrast, the increase in fiber length when active is greater than would be expected from the admittedly sparse literature on this subject. The results of this study are discussed largely in relation to two points of neurophysiological interest: the physiological range of muscle stretch as it pertains to the responsiveness of muscle spindles and tendon organs; and those mechanical aspects of lengthening contractions that give insight into the neural control of stepping. For exciting both spindles and tendon organs passive muscle stretch and shortening contractions are shown to be relatively ineffective and lengthening and isometric contractions particularly effective movements. It is suggested that, just as recent literature has emphasized the co‐activation of efferent alpha and gamma motoneurons as a muscle becomes active, so too is there a synchronous activation of afferents, particularly the Ia and group II endings of muscle spindles and Ib endings of tendon organs. Finally the thesis is advanced that, while it has been convenient to separate E ² from E ³ in the description of the stance phase of the step cycle, extensor muscles are actually undergoing a single mechanical event: an active stretch‐shorten cycle for knee and ankle extensors and an active isometric‐shorten cycle for hip extensors. This hypothesis has significant implications for the neural control program that regulates the stepping sequence in that it emphasizes the extent to which appropriate changes must be preprogrammed in the mechanical properties of muscles for the smooth execution of stepping.
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.
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.