Handgrip strength: a predictive indicator of upper body maximal strength?

In the last few years, Handgrip strength has been widely recognized as a relevant indicator of physical function, nutritional status and quality of life in a clinical population. The validity of this indicator has been reported in many experimental and epidemiological investigations, showing a significant association of this value with several physiological and not physiological parameters. Bone health, functional capacity, nutritional status as well as postoperative complications, increased length of hospitalization and higher rehospitalisation rate are all elements found to be strongly associated with an acceptable or with an impaired grip strength. These outcomes, as well as the possibility to estimate this value in an easy and not invasive way through the use of specifically designed dynamometers, might represent the mains reason why this practice is gaining increasingly attention. However, the scientific literature is still lacking of knowledge regarding the use of this indicator within a general healthy and physically active population. In spite of some studies trying to establish normal reference values for handgrip strength in healthy subjects according to age, gender and anthropometric characteristics (weight and height), no studies can be found investigating this concept in relation to fitness and sport performance. The possibility to use the handgrip strength as an indicative value of some specific physical qualities, such as the upper body maximal strength (expressed in terms of 1RM bench press), can be considered an unexplored field and its development might represent a relevant support for the strength and conditioning professionals. Therefore, we hypothesize that a significant association might be found between handgrip strength, body composition and upper body maximal strength and that this association might be used as a specific “performance predictor”. Accordingly, we have started a pilot study to examine possible critical aspects to be considered in the design of a larger controlled trail. The main idea is to collect a sufficiently wide and heterogeneous sample of data to support the development of a 1RM bench press prediction equation based on subjects’ handgrip performance. Fifteen healthy subjects (8 men / 7 women; age 25.53 ± 7.14 yr; body mass 65.58 ± 13.26 kg; height 167±10 cm) without habitual intensive exercise participated in this pilot intervention. Body composition, handgrip strength and maximal body upper strength were evaluated. Subjects’ body composition was estimated through a bioelectrical impedance analysis (BIA 101, Akern srl, Florence, Italy) and resulted in a mean value of 22.12 ± 8.64% of fat and 77.81 ± 8.5%1 of lean mass. Handgrip strength was estimated for both dominant and not dominant side, respectively (39.27 ± 14.52 w; 37.59 ± 13.49 w) through the use of a handgrip dynamometer (Kern map, Sinergica Soluzioni, Montesilvano, Italy). The test was performed two times for each side and values were averaged. Subjects’ upper body strength was tested using a bench press 1RM test. Subjects performed a standardized warm up consisting of 1 set of 15 reps with no load (only the barbell). Then they were asked to perform a set of as many reps as possible with a workload corresponding to one-third of the subject’s body mass. The result of this set (in terms of workload and number of reps) was used to predict subject’s 1RM using the Mayhew’s equation. The purpose of predicting a 1RM was to minimize fatigue in subsequent 1RM tests. Finally, after a 5 min rest, subjects performed an attempt with the maximal predicted workload. After each successful attempt, the load was increased by 2–5% until failure of lifting the load in 2–3 following attempts. The rest period between each attempt was 5 minutes. Subjects’ maximal strength resulted in an average of 49.21 ± 23.87 kg. All BIA, handgrip and 1RM testing were overseen by the same investigator and conducted with the same equipment. Subjects were assessed at the same time of day to account for diurnal variation. Each subject was instructed to refrain from any strenuous activities for 72 hours before testing day. Following the intervention, data were used for statistical analysis using the STATISTICA Software package© for Windows©. In a simple linear regression analysis, a significant association between handgrip strength and upper body maximal strength was observed (r= 0.77; p= 0.0007). A multiple regression analysis shown a not significant association between the body composition and handgrip strength (p= 0.81). These preliminary results shown that the handgrip strength might be associated to the individual maximal strength performance and it might be considered as a valid predictor of upper body strength performance within a sport/fitness context. Although the presented pilot intervention cannot draw any conclusion on the topic, due to the limited sample analysed, it represented a relevant support in the design of a larger controlled trial that is currently undertaken with a larger representative population to strengthen the evidence for this hypothesis. This approach might open to a deeper and more comprehensive discussion on the development of a specific linear regression model.