J Lönn

Umeå University, Umeå, Västerbotten, Sweden

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Publications (4)7.76 Total impact

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    ABSTRACT: It is well known that proprioception is composed of the senses of movement and position. Whereas tests of position sense are quite commonly used, tests of the acuity in perception of movement velocity are scarce. In the present study we examined some novel tests for assessing the sense of limb movement velocity, involving replication and discrimination of single-joint movement velocity. Specifically, we investigated: (1) whether replication of limb movement velocity is more accurate following active criterion movements as compared to passive; (2) whether antagonist muscle contraction during passive limb movement enhances velocity discrimination; (3) how criterion movement velocity influences response accuracy; (4) the relationship between movement velocity and movement extent during velocity replication; and (5) whether subjects really base discrimination of velocities on perceived velocity. Sixteen healthy subjects participated in four tests (I-IV). For each test, horizontal abductions were performed about the right glenohumeral joint from the sagittal plane. The subjects were required to actively replicate the velocity of either an active (Test I) or passive (Test II) criterion movement, or judge whether a passive/semipassive (passive during antagonist muscle contraction) movement was faster or slower than a previous passive/semipassive criterion movement (Test III/IV). The results revealed higher response accuracy for Test I compared to Test II and for slower movements compared to faster, but no difference in response accuracy between Test III and IV. For velocity discrimination, the analysis revealed that the subjects based their judgment on the difference between criterion and comparison velocity rather than time or extent cues.
    Somatosensory and Motor Research 02/2001; 18(1):76-82. · 0.93 Impact Factor
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    ABSTRACT: To assess the effect of starting position, target position, and various types of limb displacement on repositioning tests commonly used for clinical evaluation of rehabilitation. Controlled laboratory environment. Sixteen healthy volunteer subjects. Absolute error, ie, the absolute difference between target and replicate positions. Each subject performed four testing procedures consisting of different types of limb displacement (active, passive, and passive during antagonist muscle contraction). For each procedure, horizontal movements were performed ipsilaterally about the right glenohumeral joint from one intermediate starting position (40 degrees ) and two extreme starting positions (0 degrees and 80 degrees ). Four fixed target positions (16 degrees , 32 degrees, 48 degrees , 64 degrees ) were presented for each starting position. The subjects were required to replicate target position after returning to the respective starting position. Lower repositioning errors occurred with active displacement procedures compared with passive, and with the intermediate starting position compared with the extreme. Target position, however, had no effect on repositioning errors. Starting position and type of displacement should be considered in interpretations and comparisons of data from clinical studies.
    Archives of Physical Medicine and Rehabilitation 06/2000; 81(5):592-7. · 2.36 Impact Factor
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    ABSTRACT: Position sense testing has increased as a tool for augmenting evaluation of joint injury. In the present study, we investigated the inter-day reliability for four different types of position sense tests using a fully automated system. The tests included (1) passive presentation/active replication, (2) passive presentation/passive replication, (3) semi-passive presentation/semi-passive replication (where semi-passive denotes passive movement during antagonist muscle contraction), and (4) active presentation/active replication. The absolute difference between presented target and replicated position was used as a measure of position sense accuracy. Ten healthy subjects who were blindfolded and seated with the arm in a moveable rig performed the tests on two occasions, separated by 3-4 days. For each type of position sense test, horizontal abduction from a starting position of 0 degrees (relative to the sagittal plane) to target positions of 32 degrees and 64 degrees, and horizontal adduction from a starting position of 80 degrees to 48 degrees and 16 degrees were conducted. A two-way ANOVA revealed no differences in absolute error between days or between testing procedures. However, intra-class correlations (ICC), which are most often used to express test-retest reliability, were moderate at best, ranging from 0.40 to 0.61 for the four types of position sense tests. Hence, the present study indicates that the ability of repositioning tests to detect alterations in proprioceptive function is limited, suggesting that their use in clinical evaluation be approached with prudence.
    Clinical Physiology 02/2000; 20(1):30-7.
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    ABSTRACT: The purpose of this study was to investigate alterations in the movement sense acuity during localized muscle fatigue in the human dominant shoulder. Fourteen healthy volunteers (8 males and 6 females) with a mean age 23 +/- 2 yr participated in the study. The subjects' ability to discriminate movement velocity relative to a reference velocity imposed over the dominant shoulder was tested following two experimental conditions: 1) Light exercise (LE), repetitive isokinetic horizontal flexion/extensions at the shoulder, ranging from 85 degrees to 20 degrees relative to the frontal plane, at 10% of maximal voluntary contraction (MVC) and 2) Hard exercise (HE), same movements as in LE, but performing MVC to fatigue. The results showed that subjects had a lower probability of distinguishing between different movement velocities following HE as compared with those during the LE condition (P < 0.001). When genders were compared, female subjects had a lower probability of distinguishing correctly than male subjects (P < 0.001). The acuity of the movement sense in the dominant shoulder is reduced in the presence of shoulder muscle fatigue. The possible influence of muscle fatigue via peripheral muscle receptors on movement sense is discussed.
    Medicine &amp Science in Sports &amp Exercise 07/1999; 31(7):1047-52. · 4.48 Impact Factor