Jesper Augustsson

Patellofemoral pain syndrome: a review of current issues.

AbstractThere is no clear consensus in the literature concerning the terminology, aetiology and treatment for pain in the anterior part of the knee. The term ‘anterior knee pain’ is suggested to encompass all pain-related problems. By excluding anterior knee pain due to intra-articular pathology, peripatellar tendinitis or bursitis, plica syndromes, Sinding Larsen’s disease,Osgood Schlatter’s disease, neuromas and other rarely occurring pathologies, it is suggested that remaining patients with a clinical presentation of anterior knee pain could be diagnosed with patello-femoral pain syndrome (PFPS). Three major contributing factors of PFPS are discussed: (i) malalignment of the lower extremity and/or the patella; (ii) muscular imbalance of the lower extremity; and (iii) overactivity.The significance of lower extremity alignment factors and pathological limits needs further investigation. It is possible that the definitions used for malalignment should be re-evaluated, as the scientific support is very weak for determining when alignment is normal and when there is malalignment. Consequently, pathological limits must be clarified, along with evaluation of risk factors for acquiring PFPS.Muscle tightness and muscular imbalance of the lower extremity muscles with decreased strength due to hypotrophy or inhibition have been suggested, but remain unclear as potential causes of PFPS. Decreased knee extensor strength is a common finding in patients with PFPS. Various patterns of weaknesses have been reported, with selective weakness in eccentric muscle strength, within the quadriceps muscle and in terminal knee extension. The significance of muscle function in a closed versus open kinetic chain has been discussed, but is far from well investigated. It is clear that further studies are necessary in order to establish the significance of various strength deficits and muscular imbalances, and to clarify whether a specific disturbance in muscular activation is a cause or an effect (or both) of PFPS.The most common symptoms in patients with PFPS are pain during and after physical activity, during bodyweight loading of the lower extremities in walking up/down stairs and squatting, and in sitting with the knees flexed. However, the source of patello-femoral pain in patients with PFPS cannot be sufficiently explained. There are several types of clinical manifestation of pain, and therefore a differentiated documentation of the patient’s pain symptoms is necessary. The connection between strength, pain and inhibition, as well as between personality and pain, needs further investigation.Many different treatment protocols are described in the literature and recent studies advocate a comprehensive treatment approach allowing for an individual and specifically designed treatment. Surgical treatment is rarely indicated.It is strongly suggested that, when presenting studies on PFPS, a detailed description should be provided of the diagnosis, inclusion and exclusion criteria of the patients should be specified along with a detailed methodology, and the conclusions drawn should be compared with those of other studies in the published literature. As this is not the case in most studies on PFPS found in the literature, it is only possible to make general comparisons. In order to further develop treatment models for PFPS we advocate prospective, randomised, controlled, long term studies using validated outcome measures. However, there is a strong need for basic research on the nature and aetiology of PFPS in order to better understand this mysterious syndrome.

The Influence of Frequency, Intensity, Volume and Mode of Strength Training on Whole Muscle Cross-Sectional Area in Humans

Strength training is an important component in sports training and rehabilitation. Quantification of the dose-response relationships between training variables and the outcome is fundamental for the proper prescription of resistance training. The purpose of this comprehensive review was to identify dose-response relationships for the development of muscle hypertrophy by calculating the magnitudes and rates of increases in muscle cross-sectional area induced by varying levels of frequency, intensity and volume, as well as by different modes of strength training.Computer searches in the databases MEDLINE, SportDiscus® and CJNAHL® were performed as well as hand searches of relevant journals, books and reference lists. The analysis was limited to the quadriceps femoris and the elbow flexors, since these were the only muscle groups that allowed for evaluations of dose-response trends. The modes of strength training were classified as dynamic external resistance (including free weights and weight machines), accommodating resistance (e.g. isokinetic and semi-isokinetic devices) and isometric resistance. The subcategories related to the types of muscle actions used. The results demonstrate that given sufficient frequency, intensity and volume of work, all three types of muscle actions can induce significant hypertrophy at an impressive rate and that, at present, there is insufficient evidence for the superiority of any mode and/or type of muscle action over other modes and types of training. Tentative dose-response relationships for each variable are outlined, based on the available evidence, and interactions between variables are discussed. In addition, recommendations for training and suggestions for further research are given.

Single-leg hop testing following fatiguing exercise: reliability and biomechanical analysis

A fatiguing exercise protocol was combined with single‐leg hop testing to improve the possibilities of evaluating the effects of training or rehabilitation interventions. In the first test–retest experiment, 11 healthy male subjects performed two trials of single‐leg hops under three different test conditions: non‐fatigued and following fatiguing exercise, which consisted of unilateral weight machine knee extensions at 80% and 50%, respectively, of 1 repetition maximum (1 RM) strength. Intraclass correlation coefficients ranged from 0.75 to 0.98 for different hop test conditions, indicating that all tests were reliable. For the second experiment, eight healthy male subjects performed the fatiguing exercise protocol to investigate how fatigue influences lower‐extremity joint kinematics and kinetics during single‐leg hops. Hip, knee and ankle joint angles, moments and powers, as well as ground‐reaction forces were recorded with a six‐camera, motion‐capture system and a force platform. Recovery of hop performance following the fatiguing exercise was also measured. During the take‐off for the single‐leg hops, hip and knee flexion angles, generated powers for the knee and ankle joints, and ground‐reaction forces decreased for the fatigued hop conditions compared with the non‐fatigued condition (P<0.05). Compared with landing during the non‐fatigued condition, hip moments and ground‐reaction forces were lower for the fatigued hop conditions (P<0.05). The negative joint power was two to three times greater for the knee than for the hip and five to 10 times greater for the knee than for the ankle during landing for all test conditions (P<0.05). Most measured variables had recovered three minutes post‐exercise. It is concluded that the fatiguing exercise protocol combined with single‐leg hop testing was a reliable method for investigating functional performance under fatigued test conditions. Further, subjects utilized an adapted hop strategy, which employed less hip and knee flexion and generated powers for the knee and ankle joints during take‐off, and less hip joint moments during landing under fatigued conditions. The large negative power values observed at the knee joint during the landing phase of the single‐leg hop, during which the quadriceps muscle activates eccentrically, indicate that not only hop distance but also the ability to perform successful landings should be investigated when assessing dynamic knee function.

Ischemic strength training: a low-load alternative to heavy resistance exercise?

Strength training with low loads in combination with vascular occlusion has been proposed as an alternative to heavy resistance exercise in the rehabilitation setting, especially when high forces acting upon the musculo‐skeletal system are contraindicated. Several studies on low‐to‐moderate intensity resistance exercise combined with cuff occlusion have demonstrated increases in muscle strength and size that are comparable to those typically seen after conventional high‐load strength training. However, the physiological mechanisms by which occlusion training induces increased muscle mass and strength are currently unclear, although several candidate stimuli have been proposed. Also, the long‐term safety, practicality, and efficacy of this training method are still controversial. Furthermore, recent studies have demonstrated that in some instances, tourniquet cuffs may not be necessary for relative ischemia and significant training effects to occur with resistance exercise at low‐to‐moderate loads. The aims of the present review are to summarize current opinion and knowledge regarding the physiology of ischemic strength training and to discuss some of the training and health aspects of this type of exercise. In addition, suggestions for further research are given.

Ability of closed and open kinetic chain tests of muscular strength to assess functional performance

The purpose of this study was to investigate the ability of closed and open kinetic chain tests of muscular strength to assess functional performance. Sixteen healthy male subjects, with a mean (±SD) age, body mass and height of 27±5 years, 78±9 kg and 183±9 cm, respectively, volunteered to participate in the study. In the closed kinetic chain test (involving muscles working across multiple joints), the subjects performed a 3 repetition maximum (3 RM) barbell squat. The open kinetic chain test (involving muscles working across a single joint) consisted of a concentric isokinetic knee extension at an angular velocity of 60°/s, and was performed using a Kinetic Communicator II dynamometer. The test of functional performance (vertical jump) was performed with the subject standing erect, quickly performing a countermovement jump for maximal height. Moderately strong significant (P<0.05) correlations between the test of functional performance and the closed and open kinetic chain tests of muscular strength were noted, r=0.51 and r=0.57, respectively. It is suggested that the effect of training or rehabilitation interventions should not be based exclusively on tests of muscular strength. Rather, various forms of dynamometry including functional performance tests could be recommended.

Acute effects of blood flow restriction on muscle activity and endurance during fatiguing dynamic knee extensions at low load.

Wernbom, M, Järrebring, R, Andreasson, MA, and Augustsson, J. Acute effects of blood flow restriction on muscle activity and endurance during fatiguing dynamic knee extensions at low load. J Strength Cond Res 23(8): 2389-2395, 2009-The purpose of this study was to investigate muscle activity and endurance during fatiguing low-intensity dynamic knee extension exercise with and without blood flow restriction. Eleven healthy subjects with strength training experience performed 3 sets of unilateral knee extensions with no relaxation between repetitions to concentric torque failure at 30% of the 1 repetition maximum. One leg was randomized to exercise with cuff occlusion and the other leg to exercise without occlusion. The muscle activity in the quadriceps was recorded with electromyography (EMG). Ratings of perceived exertion (RPE) and acute pain were collected immediately, and delayed onset muscle soreness (DOMS) was rated before and at 24, 48, and 72 hours after exercise. The results demonstrated high EMG levels in both experimental conditions, but there were no significant differences regarding maximal muscle activity, except for a higher EMG in the eccentric phase in set 3 for the nonoccluded condition (p = 0.005). Significantly more repetitions were performed with the nonoccluded leg in every set (p < 0.05). The RPE and acute pain ratings were similar, but DOMS was higher in the nonoccluded leg (p < 0.05). We conclude that blood flow restriction during low-intensity dynamic knee extension decreases the endurance but does not increase the maximum muscle activity compared with training without restriction when both regimes are performed to failure. The high levels of muscle activity suggest that performing low-load dynamic knee extensions in a no-relaxation manner may be a useful method in knee rehabilitation settings when large forces are contraindicated. However, similarly to fatiguing blood flow restricted exercise, this method is associated with ischemic muscle pain, and thus its applications may be limited to highly motivated individuals.

Effects of Vascular Occlusion on Muscular Endurance in Dynamic Knee Extension Exercise at Different Submaximal Loads

Strength training with low load under conditions of vascular occlusion has been proposed as an alternative to heavy-resistance exercise in the rehabilitation setting, when large forces acting upon the musculoskeletal system are unwanted. Little is known, however, about the relative intensity at which occlusion of blood flow significantly reduces dynamic muscular endurance and, hence, when it may increase the training effect. The purpose of this study was to investigate endurance during dynamic knee extension at different loads with and without cuff occlusion. Sixteen subjects (20–45 years of age) with strength-training experience were recruited. At 4 test sessions, the subjects performed unilateral knee extensions to failure with and without a pressure cuff around the thigh at 20, 30, 40, and 50% of their 1 repetition maximum (1RM). The pressure cuff was inflated to 200 mm Hg during exercise with occlusion. Significant differences in the number of repetitions performed were found between occluded and nonoccluded conditions for loads of 20, 30, and 40% of 1RM (p < 0.01) but not for the 50% load (p = 0.465). Thus, the application of a pressure cuff around the thigh appears to reduce dynamic knee extension endurance more at a low load than at a moderate load. These results may have implications regarding when it could be useful to apply a tourniquet in order to increase the rate of fatigue and perhaps also the resulting training effect. However, the short- and long-term safety of training under ischemic conditions needs to be addressed in both healthy and less healthy populations. Furthermore, the high acute pain ratings and the delayed-onset muscle soreness associated with this type of training may limit its potential use to highly motivated individuals.

Injuries and preventive actions in elite Swedish volleyball.

The purpose of this study was to examine the prevalence of injury and the extent of preventive actions in elite Swedish volleyball players. Injuries to players in the elite male and female Swedish division, during the 2002–2003 season, were registered by using a questionnaire. Of the 158 volleyball players (70% response rate), a total of 82 players (52%) reported 121 injuries, during a total exposure time of 24 632 h, representing an overall incidence of 0.77 injuries per player. The majority of the injuries were located in the ankle (23%), followed by the knee (18%) and the back (15%). Most injuries (62%) were classified as being of minor severity. Most injuries occurred during training (47%), and 41% of the injuries had a gradual onset. Fifty‐four percent of the injuries that could be related to a specific court situation occurred during blocking, and 30% during spiking. Most players (96%) participated in injury prevention training of some kind, generally performed without supervision (58%).

Gender differences and reliability of selected physical performance tests in young women and men

Although push-ups and sit-ups are among the most commonly used body-weight exercises to improve and assess strength and fitness, there is a lack of reproducible test protocols in the scientific literature. The aim of this study was to evaluate the test–retest reliability of sit-ups and push-ups and to determine performance differences in muscular endurance (maximal number of repetitions) and power (timed, maximal number of repetitions in 30 s) in young women and men. Thirty-eight women and 25 men, 18–35 years of age, participated in the study. Thirteen women participants performed two test sessions of each test using a test–retest design. A high reliability was noted for both the sit-up and the push-ups tests (intraclass correlation values ranged from 0.92 to 0.95). There were no significant differences between the men and the women in the mean number of sit-ups (42 and 41 repetitions respectively for endurance and 16 and 14 repetitions respectively for power), whereas the men performed significantly more push-ups than the women (39 and 17 repetitions respectively for endurance and 29 and 13 repetitions respectively for power). In conclusion, sit-ups and push-ups are tests with high reliability, which are easy to perform and may therefore be recommended for clinical use to evaluate muscular endurance and power in young men and women. Moreover, the fact that men performed twice as many push-ups as women indicates that, when designing training programme for women, attention should be turned towards strengthening exercises of the upper body.

Documentation of strength training for research purposes after ACL reconstruction

PurposeThe purpose of this systematic literature review was to evaluate strength training protocol documentation during rehabilitation after anterior cruciate ligament (ACL) reconstruction. The aim was further to present recommendations concerning what components (i.e. methods, principles and training variables) could be considered vital to document when it comes to strength training for research purposes after ACL reconstruction.MethodsA search of the PUBMED/MEDLINE, CINAHL and SportDiscus databases was made of relevant literature relating to strength training after ACL reconstruction. The database search was based on relevant medical subject headings terms (strength/resistance/weight training, anterior cruciate ligament reconstruction/rehabilitation). The literature was reviewed regarding the way methods and variables were documented in strength training protocols during rehabilitation after ACL reconstruction in peer-reviewed original prospective articles.ResultsThe systematic literature search identified 139 citations published between January 1983 and May 2012. Six studies contained a strength training programme-part of the rehabilitation protocol after ACL reconstruction that met the inclusion criteria. Basic information (i.e. training frequency, intensity, volume, progression or the duration of the training period) regarding the strength training protocols used during rehabilitation after ACL reconstruction was not documented in full in four of the studies.ConclusionThe results clearly indicate the need of a more standardised and detailed way of documenting strength training for research purposes after ACL reconstruction in order to increase the value of future studies on this subject. This review gives recommendations on strength training protocol documentation after ACL reconstruction to facilitate this goal.Level of evidenceIV.