Zeevi Dvir

Dvir, Z and Müller, S. Multiple-joint isokinetic dynamometry: a critical review. J Strength Cond Res 34(2): 587–601, 2020—Angular isokinetic dynamometry (AID) is widely regarded as the gold standard for dynamic muscle performance testing. Based on the rotational movement of its actuator, AID targets “single-joint” (knee, shoulder, hip, etc.) configurations namely measurement of muscle potential while it moves the lever arm-limb assembly ostensibly around a single fixed axis. On the other hand, the application of multiple-joint isokinetic dynamometry (MID) is relatively narrow, both in research and in practice. This situation is due, possibly, to the fact that these dynamometers are generally more limited in scope namely to testing/conditioning of combined hip, knee, ankle motion (leg press), combined shoulder, elbow motion, and lifting motion patterns, despite the fact that all 3 are associated with higher functionality. However, with the emerging importance of MID, this critical review takes a fresh look at its various aspects including the terminology and classification of multiple-joint isokinetic dynamometers; the problem of scaling namely the need to adjust the range of motion and linear velocities to subjective anthropometric measures; specific technical and methodological issues that underlie the valid application of these dynamometers; available reference values; and the reproducibility of MID-based test findings. Analysis of these topics indicates that MID may validly and effectively be applied for the assessment and conditioning of specific muscle action patterns. However, there is a clear need for standardization of tests and for conditioning protocols alongside research into the use of this method in various clinical cohorts.

The valid confirmation of a positive change (improvement) in a patient's health status due to intervention has been at the core of medicine and rehabilitation since their very inception as clinicians always aspired to ensure that treating their patients had led to successful outcomes both in acute and chronic conditions. However what is change: either improvement or worsening (aggravation), is a complicated issue which involves clinical as well as statistical considerations. Change invariably relates to a difference in some measurable entity and almost always it relates to a time span. The confirmation of clinical change is important both for varying the treatment course (if necessary) and for the termination of treatment when the latter has reached wither its prescribed objective or a plateau. Since in the context of rehabilitation, the outcome measures (OM) are strongly linked to performance, determination of change in the latter is confounded by many factors, collectively known as the error of measurement, which render a decision regarding clinically meaningful change, highly involved. This is further complicated by the stability of the observed OM, the so-called reproducibility of the OM, and the accuracy of the measurement instrument. The higher the reproducibility the lower is the error. Moreover, in order to proclaim change, in most cases a positive one, it is necessary for the difference in outcome scores (i.e. the change) to surpass the error of measurement, in varying degree of rigor. This paper describes selected methods associated with determination of change and focuses predominantly on the difference between a simple difference in scores ('simple change'), a significant difference in scores and the so-called clinically meaningful change in scores which is considered today as the benchmark for confirmation of a real change.

OBJECTIVES: To assess the strength of the flexors and extensors of the knee and hip joints in elderly and in young individuals. METHODS: A group of elderly women (N=47) and men (N=44) aged 65 and older and a group of young women (N=15) and men (N=15) aged between 20 and 30 years were tested for the isokinetic strength of the hip and knee flexors and extensors. RESULTS: A typical age-related decrease in the strength of all tested muscles was observed but the decline in hip muscles strength, compared to those of the knee, was significantly lower, by about 10%. Moreover, women presented a significantly better strength preservation than men. The consistency of performing the repeated isokinetic efforts was higher, in some instances significantly so, in the older (range: 4.4–11%) than in the younger (3.5–6.3%) individuals but the differences do not seem to convey any clinical significance. CONCLUSION: These findings enable clinicians to set valid rehabilitation goals, particularly with respect to hip dysfunction in the elderly. Furthermore, healthy elderly individuals perform maximal isokinetic tests with substantially similar degree of gross motor control compared to that of young individuals.

Abdominal surgery with bowel resection through a midline or transverse incision is performed in most cases of colorectal cancer (CRC). Both incisions affect abdominal wall function and may lead to differences in postoperative clinical outcomes. Although postoperative isometric trunk flexion strength (ITFS) has previously been investigated, the results were based on measurement tools distinguished by poor reproducibility and validity. To evaluate the reproducibility of and variations in ITFS following abdominal surgery using a dynamometer and explore the correlation between ITFS and the scar length. The study group consisted of 22 consecutive patients (15 men and 7 women) referred for surgery. The outcome parameters included ITFS which was measured using a fixed dynamometer and a digital manometer, scar length, weight and pain. Test–retest measurement (3 h apart) of ITFS was taken 1 day before surgery to determine the instruments’ reproducibility. Additional measurements of the outcome parameters were taken 1 and 6 weeks postoperatively. Excellent test–retest correlations (ICC > 0.85) coupled with low standard error of the measurement for both the ITFS and the manometric findings indicated clinically acceptable reproducibility of the findings. Significant pre- and postoperative differences in ITFS were noted using both techniques. Six weeks postoperatively, fair and significant correlations were noted between the dynamometry-based ITFS and both the scar length (r = 0.452) and age (r = 0.498). Of note, scar length and preoperative dynamometric ITFS predicted ITFS 6 weeks postoperatively (F = 102.949, p < 0.001, R ² = 0.92). Measurements of ITFS using dynamometry in elective CRC patients are reproducible, sensitive to clinical changes and allow prediction of postoperative ITFS scores based on their preoperative counterparts.

Background: Outcome measures of operative intervention for ankle fractures indicate poor subjective and objective results. Though patients regain full range of motion they often complain of pain and fatigability. Specifically, there is a paucity of data regarding strength characteristics of the relevant muscles after surgical intervention. Objective: Describe the strength characteristics of ankle invertors(INs) and evertors (EVs) and explore their relationship to the ankle-hindfoot scale (AHS) in patients after surgical intervention for ankle fractures. Method: Bilateral isokinetic concentric and eccentric INs and EVs strength was measured in 24 patients, 6–12 months following surgery. Additional subjective and objective factors were evaluated using the AHS. Results: Strength of the involved limb muscles was significantly lower compared to the contra-lateral muscles (p<0.0001). However, strength reduction was significantly greater in the INs (27.6–37.5%) than the EVs(14.4–24.3%), (p=0.0005). The EVs/INs ratio of the uninvolved limb(89–102%) was significantly lower than the ratio of the involved limb(111–141%), (p<0.0001). The clinical status of the limb was found to have a significant effect on all dynamic control ratios (DCRs): EVR(E)/INV(C), INV(E)/EVR(C), EVR(C)/INV(E), and INV(C)/EVR(E) (P<0.0001, P=0.0032, P=0.0001, and P=0.0015, respectively). A significant relationship was found between the mean AHS score and relative unilateral weakness (r=−0.58, p=0.003). Conclusions: Strength reduction could be one of the reasons for the functional decline following ankle fractures. The weakness of the INs muscles of the ankle is more pronounced than that of the EVs.

Neck muscles are responsible for directing the head and for maintaining its posture. As a result, the muscular mechanical output is correspondingly moderate but not insignificant as evidenced by a positive therapeutic effect when reconditioning is indicated. Cervical muscle strength (CS) measurement and interpretation occupy a unique niche in the domain of muscle performance. Due to the wide variety of devices and protocols, a vast range of strength scores has been reported, denying the formation of reliable reference values. A literature search based on the keywords "cervical/head/neck" strength was conducted. The search yielded 34 relevant papers which were reviewed according to preset criteria. Overall studies indicate that compared to normal subjects patients suffering from neck-related disorders present with significant reduction in CS, whereas women are weaker than men by about 40%. Noteworthy a significant drop in CS in both sexes is delayed until the seventh decade. In terms of its reproducibility, CS findings have been investigated using primarily relative parameters, and hence, the associated error is not yet established. Therefore, application of CS as a clinical outcome measure, particularly for assessing change due to intervention, should be critically conducted.

Grip, Key Pinch (KP), 3 Point Pinch (3PP) and 2 Point Pinch (2PP) strengths were measured twice weekly in 32 women with primary osteoarthritis of the hand (POAH) and 25 healthy women. Reproducibility was assessed by standard error of measurement (SEM) and the coefficient of variation (CV). Cutoff values for significant improvement or deterioration were determined and expressed, respectively, as either the smallest detectable difference (SDD) or critical difference (CD). The SDD and CD of grip and pinch strengths were higher in POAH patients than in the healthy group. Among the pinch tests the 2PP findings were least reproducible. The relatively high SDD and CD scores indicate that improvement may be detected only in patients with moderate to severe weakness of grip and pinch. Furthermore, in POAH patients, diagnosing strength changes using the 2PP test is invalid due to low reproducibility.